JP3307582B2 - Brushless motor drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet field type brushless motor drive circuit, and more particularly to a brushless motor capable of driving a plurality of brushless motors without using a magnetic field position sensor of a field. It relates to a drive circuit.

[0002]

2. Description of the Related Art Conventionally, a sensorless drive circuit of a brushless motor focuses on a correlation between a speed electromotive force generated in an armature winding of a rotating brushless motor and a position of a field, and uses the speed electromotive force to perform a brushless motor. The commutation timing of the motor is determined, and the brushless motor is commutated in accordance with the commutation timing, whereby the brushless motor is rotationally driven without a sensor.

[0003]

The speed electromotive force is:
It has to be detected using the armature winding voltage of the brushless motor. Therefore, when a plurality of brushless motors are connected to one brushless motor drive circuit, the armature winding voltage of each brushless motor cannot be detected individually, and the speed electromotive force of each brushless motor cannot be detected. As a result, the commutation timing of the brushless motor cannot be determined. Therefore, in a sensorless drive circuit of a brushless motor based on such a speed electromotive force, 1
There is a problem that a plurality of brushless motors cannot be connected to one circuit and driven to rotate without a sensor.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to provide a brushless motor drive circuit that can rotationally drive a plurality of brushless motors without a sensor.

[0005]

In order to achieve this object, a brushless motor drive circuit according to claim 1 comprises a plurality of switching elements for sequentially supplying a DC voltage to a plurality of armature windings of a brushless motor. And an energization control circuit that turns on or off a plurality of switching elements of the inverter circuit to perform commutation and rotate the brushless motor, and further connects a plurality of brushless motors to the inverter circuit. And a current for converting a current flowing through the armature windings of the plurality of brushless motors connected to the inverter circuit by the connection circuit into at least one voltage for each energized phase and converting the current into a voltage. A plurality of brushless modes based on a detection circuit and a detection voltage of the current detection circuit.
Commutation of 1 for the total current flowing through the armature windings of the
Detecting the second current increase region in the cycle and detecting the same
And a commutation command circuit that outputs a commutation command to the energization control circuit at the specified timing and commutates the plurality of brushless motors.

When the brushless motor rotates, the positional relationship between the field of the motor and the energized armature winding changes. With this change, the value of the current flowing through the armature winding also changes. The brushless motor driving circuit according to the first aspect enables sensorless driving of the brushless motor by determining the commutation timing by paying attention to such a change in the armature current. Specifically, as shown in FIG. 1, when the armature winding is energized while the brushless motor is being driven, the value of the current flowing through the armature winding shows a remarkable increase twice (41, 42). ). Therefore, the commutation timing is determined by detecting the second remarkable current increase region 42 (second current increase region).

That is, according to the brushless motor driving circuit of the present invention, the switching elements of the inverter circuit are connected to the armature windings of the plurality of brushless motors connected to the inverter circuit by the connection circuit by the conduction control circuit. While being turned on, an armature current flows. The armature current of all brushless motors is
At least one voltage is converted into one for each energized phase and detected, and based on the detected voltage , the current flowing through the armature windings of the plurality of brushless motors by the commutation command circuit
The arrival of the second current increase region in one commutation cycle is detected for the total value of . A commutation command is output from the commutation command circuit to the conduction control circuit at the timing of the arrival of the second current increase region, and the switching element of the inverter circuit is turned on or off by the conduction control circuit based on the commutation command. Is done. As a result, commutation to the brushless motor is performed, and the plurality of brushless motors are driven without a sensor.

According to a second aspect of the present invention, in the brushless motor driving circuit according to the first aspect, the commutation command circuit includes an averaging circuit for averaging the output of the current detection circuit, and the current detection circuit. A commutation command output circuit that outputs a commutation command to the energization control circuit when the output of the circuit becomes a predetermined multiple of the output of the averaging circuit.

According to a third aspect of the present invention, in the brushless motor driving circuit according to the first aspect, the commutation command circuit includes a sampling circuit for extracting an instantaneous output of the current detection circuit, and the current detection circuit. And a commutation command output circuit for outputting a commutation command to the energization control circuit when the output of the control circuit becomes a predetermined multiple of the extraction value of the sampling circuit.

According to a fourth aspect of the present invention, in the brushless motor driving circuit according to the third aspect, the sampling circuit extracts the instantaneous output of the current detection circuit every time a commutation operation is performed by the conduction control circuit. Is what is done.

According to a fifth aspect of the present invention, in the brushless motor driving circuit according to the third or fourth aspect, the instantaneous output of the current detection circuit is extracted by the sampling circuit by increasing the first armature current. This is performed after the region and before the second armature current increase region.

According to a sixth aspect of the present invention, in the brushless motor driving circuit according to any one of the first to fifth aspects, the switching element of the inverter circuit, which is turned on by the energization control circuit, is controlled by chopper control. A chopper control circuit for turning on or off, and storing an output voltage of the current detection circuit in synchronization with an on operation of the switching element of the inverter circuit by the chopper control circuit, and replacing the stored voltage with the current detection circuit. And a speed changing circuit for changing the on / off duty ratio of the chopper control circuit to change the rotation speed of the plurality of brushless motors.

According to a seventh aspect of the present invention, in the brushless motor driving circuit according to the sixth aspect, the speed changing circuit is for setting target speeds of the plurality of brushless motors. A speed detection circuit that detects an actual speed of the brushless motor based on a commutation command output from a flow command circuit; and a real speed detected by the speed detection circuit and a target speed set by the speed change circuit. A speed correction circuit that changes an on-off duty ratio of the chopper control circuit based on the actual speed of the plurality of brushless motors to a target speed.

According to the brushless motor drive circuit of the present invention, the brushless motor operates in the same manner as the brushless motor drive circuit of the sixth embodiment, and the actual speed of the brushless motor is:
The speed is detected by the speed detection circuit based on the commutation command.
On the other hand, the target speed of the brushless motor is set by a speed changing circuit. The actual speed and the target speed are fed back to the speed correction circuit, and the speed correction circuit changes the on / off duty ratio of the chopper control circuit based on the two speeds, thereby correcting the actual speed of the brushless motor to the target speed. .

According to an eighth aspect of the present invention, in the brushless motor driving circuit according to any one of the second to seventh aspects, when the plurality of brushless motors are started, the plurality of brushless motors generate starting torque. A commutation command output circuit that outputs a sufficient voltage to the commutation command output circuit in place of the averaging circuit or the sampling circuit. When the output voltage of the wave removing circuit becomes a predetermined multiple of the output voltage of the starting compensation circuit, a commutation command is output to the energization control circuit.

According to a ninth aspect of the present invention, in the brushless motor driving circuit according to the sixth or seventh aspect, the on-duty ratio of the switching element of the inverter circuit by the chopper control circuit is less than a predetermined value. A start compensation circuit that outputs a voltage sufficient for the plurality of brushless motors to generate a start torque to the commutation command output circuit instead of the averaging circuit or the sampling circuit every time the value becomes equal to or more than the value. The commutation command output circuit outputs a commutation command to the energization control circuit when the output voltage of the harmonic elimination circuit becomes a predetermined multiple of the output voltage of the start compensation circuit. .

According to the brushless motor driving circuit of the ninth aspect, the operation is the same as that of the brushless motor driving circuit of the sixth or seventh aspect, and the ON duty ratio of the chopper control circuit is reduced to less than a predetermined value. Therefore, even if the plurality of brushless motors stop or rotate at a low speed, if the ON duty ratio is increased to a predetermined value or more thereafter, the plurality of brushless motors are sent from the start compensation circuit to the commutation command output circuit. A voltage sufficient to generate the starting torque is output. Therefore, the plurality of brushless motors once stopped or rotated at a low speed are restarted accurately.

According to a tenth aspect of the present invention, in the brushless motor driving circuit according to any one of the first to ninth aspects, each time a commutation instruction is output from the commutation instruction circuit to the energization control circuit. And a zero reset circuit for artificially resetting the output voltage of the current detection circuit or the harmonic elimination circuit output to the commutation command circuit to approximately zero volts.

[0019]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. The principle of operation of the brushless motor drive circuit in this embodiment is described in Japanese Patent Application No. 7-207665, and a description thereof will be omitted.

FIG. 2 shows a sensorless DC according to this embodiment.
FIG. 2 is a circuit diagram of a brushless motor drive circuit 1; This motor drive circuit 1 is used for variable-speed operation of a small PM brushless motor for an indoor fan, a transport device in which a load torque can change suddenly, and a brushless motor for an outdoor fan of an air conditioner that is easily affected by a gust or the like. As a sensorless drive circuit. The brushless motor 51 to be driven in the present embodiment is a surface magnet type brushless motor in which a field of a permanent magnet is a rotor and a three-phase armature winding is a stator. It should be noted that a motor with a slip ring in which an armature winding is a rotor with a field as a stator, a brushless motor of an embedded magnet type, and an outer rotor motor in which a stator is provided inside and a rotor is provided outside. This motor drive circuit 1 can be used.

The motor drive circuit 1 is connected with five brushless motors 51 of the same model in parallel via a connection circuit 52 connected to the inverter circuit 3. Motors of the same model are motors having the same speed electromotive force constant, torque constant, and inertia. The brushless motor 51 connected to one motor drive circuit 1 must be the brushless motor 51 of the same model, but if the brushless motor 51 of the same model, two or more brushless motors 51 A brushless motor 51 can be connected. The number of brushless motors 51 that can be connected is (maximum output current of the inverter circuit 3) /
(Maximum current of the brushless motor 51).

The auxiliary power supply circuit 2 of the motor drive circuit 1
This is a circuit that generates and outputs a stable 10-volt voltage from a 0-volt DC power supply 50. The 10-volt voltage generated by the auxiliary power supply circuit 2 is supplied as a drive voltage to each circuit such as the start-up compensation circuit 7 and the commutation instruction circuit 9.

The inverter circuit 3 is a circuit for sequentially switching 30-volt DC voltage to three-phase (U-phase, V-phase, W-phase) armature windings of a plurality (five) of brushless motors 51. It is. The source terminals of three P-MOS field-effect transistors Qu, Qv, and Qw as upper arm transistors are connected to the positive input terminal P of the DC power supply 50 of the inverter circuit 3. Have three NMs as lower arm transistors
The source terminals of the OS field effect transistors Qx, Qy, and Qz are connected to form three arms corresponding to three-phase armature windings.

The upper arm transistors Qu-Qw have their gate terminals connected to the respective outputs u-w of the distribution circuit 12 via the resistances Ru1-Rw1 of 10 kΩ. It is configured to be turned on and off (see FIG. 3B). A 47 kΩ resistor R for protecting and preventing floating of the gate voltage is provided between the gates and sources of the upper arm transistors Qu to Qw.
u2 to Rw2 and the upper arm transistors Qu to Qw corresponding to the lower arm transistors Qx to Qz when the lower arm transistors Qx to Qz are turned on by chopper control.
Is connected to the lower arm transistors Qx to Qz to prevent them from turning on at the same time.
0pF) Cu to Cw are respectively connected.

On the other hand, the gate terminals of the lower arm transistors Qx to Qz are respectively connected to the respective outputs x to z of the distribution circuit 12 via the resistors Rx1 to Rz1 of 1 k.OMEGA. It is connected to the output terminal of the chopper control circuit 18 via the terminal. Each of the inverters Ix to Iz is constituted by an open collector NPN digital transistor whose emitter terminal is connected to the ground-side input terminal N of the DC power supply 50 (that is, the circuit is grounded). Therefore, the lower arm transistors Qx to Qz are turned on and off according to the outputs x to z of the distribution circuit 12 and the output of the chopper control circuit 18. Specifically, when a low signal is output from the chopper control circuit 18 to turn off the collector and the emitter of the inverters Ix to Iz, and a high signal is output from the outputs x to z of the distribution circuit 12, The arm transistors Qx to Qz are turned on. That is, as shown in FIGS. 3A and 3B,
The lower arm transistors Qx to Qz are chopper-controlled according to the output of the chopper control circuit 18.

Note that 5.6 kΩ resistors Rx2 to Rz2 for protection and prevention of gate voltage floating are connected between the gates and sources of the lower arm transistors Qx to Qz, respectively. In addition, each arm transistor Qu
Between the source and the drain of each of the arm transistors Qu to Qz, free wheel diodes Du to Dz for circulating a current caused by a back electromotive force generated in the armature winding of the brushless motor 51 when the arm transistors Qu to Qz are turned on and off. ,
Each is connected in anti-parallel.

The current detection circuit 4 collects the currents flowing through the armature windings of the plurality (five) of the brushless motors 51,
This is a circuit for converting this into a voltage and outputting it to the harmonic elimination circuit 13. This current detection circuit 4 includes a DC power supply 50
And a shunt resistor Rs of 0.1Ω (2 W) inserted between the ground side input terminal N and the inverter circuit 2. All three-phase armature currents of the five brushless motors 51 are converted by the shunt resistor Rs except for the return currents to the freewheel diodes Du to Dz. FIG. 3C shows the brushless motor 5.
1 shows an output voltage waveform of the current detection circuit 4 during normal operation.

The harmonic elimination circuit 13 synchronizes with the chopper control by the chopper control circuit 18 to
Is a circuit for storing the output voltage of the current detection circuit 4 while the lower arm transistors Qx to Qz are on, and outputting the output voltage to the sampling circuit 5 and the commutation command circuit 9. In other words, harmonic components are removed by chopper control,
The output voltage of the current detection circuit 4 is output to the sampling circuit 5 and the commutation command circuit 9. Harmonic removal circuit 13
Represents an analog switch AS1, a capacitor C1, a resistor R3 that functions as an RC low-pass filter together with the capacitor C1, resistors R4, R5, and an operational amplifier OP.
1 and a non-inverting amplifier configured as described above.

One channel terminal of the analog switch AS1 is connected to the output terminal of the current detection circuit 4 via a 550Ω resistor R3, and the other channel terminal is connected to a 0.1 μF capacitor C1 whose one end is grounded. It is connected. The gate of the analog switch AS1 is connected to the output terminal of the chopper control circuit 18 via the inverter Ia, and while the row signal is output from the chopper control circuit 18 (the lower arm of the inverter circuit 3 is controlled by the chopper control). The analog switch AS1 is turned on while the transistors Qx to Qz are turned on. Therefore, the output voltage of the current detection circuit 4 is controlled by the lower arm transistors Qx to Qx by the chopper control circuit 18.
The data is stored in the capacitor C1 in synchronization with the ON operation of Qz. Therefore, in combination with the RC low-pass filter constituted by the resistor R3 and the capacitor C1, the output voltage of the current detection circuit 4 from which higher harmonic components have been removed by the chopper control can be stored in the capacitor C1.

The inverter Ia is constituted by an open collector type NPN type digital transistor whose emitter is grounded, and is connected to a 10 volt output of the auxiliary power supply circuit 2 via a 1 kΩ pull-up resistor R6. .

The non-ground terminal of the capacitor C1 is connected to the non-inverting input terminal of the operational amplifier OP1. This operational amplifier OP1 forms a non-inverting amplifier together with the resistors R4 and R5. Since the resistance value of the resistor R4 is 47 kΩ and the resistance value of the resistor R5 is 10 kΩ, the output of the capacitor C1 is amplified by about 5.7 times by the non-inverting amplifiers OP1, R4 and R5, and its output terminal Is output to the sampling circuit 5 and the commutation command circuit 9 connected to That is,
The output voltage of the current detection circuit 4 is amplified by a factor of about 5.7 after the harmonic components are removed by the harmonic removal circuit 13 and output to the sampling circuit 5 and the commutation command circuit 9. FIG. 3D illustrates the output voltage of the harmonic elimination circuit 13.

The non-inverting amplifiers OP1, R4, R5
Can be eliminated by increasing the resistance value of the shunt resistor Rs of the current detection circuit 4. For example, the resistance value of the shunt resistor Rs is increased
When the resistance is doubled to 1Ω, the output voltage of the current detection circuit 4 is also increased by a factor of ten. Therefore, in such a case, the non-inverting amplifier OP
The output of the capacitor C1 may be output to the sampling circuit 5 and the commutation command circuit 9 without passing through R1, R4, and R5. In this embodiment, a resistor Rs having a small resistance value is used to suppress a temperature rise of the shunt resistor Rs.

The sampling circuit 5 includes the harmonic elimination circuit 1
3 is a circuit for storing the instantaneous value of the output voltage and outputting the instantaneous value to the amplifier circuit 6. Sampling circuit 5
Has an analog switch AS2, a capacitor C2, and resistors R7 and R8. Analog switch AS2
Is connected to the output terminal of the harmonic elimination circuit 13, and the other channel terminal is connected to a 1 kΩ resistor R7.
Are connected to a 0.1 μF capacitor C2 and a 1MΩ resistor R8, both ends of which are both circuit grounded. The gate of the analog switch AS2 is connected to the output terminal of the commutation command circuit 9, and while the high commutation command 56 is being output from the commutation command circuit 9 (see FIG. 3 (g)). AS2 is turned on.

The capacitor C2 is connected to the analog switch AS
2 is connected to the output terminal of the harmonic elimination circuit 13 via the resistor R7 while the switch 2 is on. This capacitor C2 is connected to a resistor R7
Together with an RC low-pass filter to remove harmonic components that cannot be completely removed by the harmonic removal circuit 13,
The output voltage of the harmonic elimination circuit 13 is stored. The non-ground terminal of the capacitor C2 is connected only to the analog switch AS2 via the resistor R7, the resistor R8, and the non-inverting input terminal of the operational amplifier OP2 of the amplifier circuit 6, and the resistance value of the resistor R8. Is very large at 1MΩ,
The voltage value of the capacitor C2 is held for a predetermined time even after the analog switch AS2 is turned off. Therefore, the voltage value (instantaneous output) of the harmonic elimination circuit 13 immediately before the analog switch AS2 is turned off is stored in the capacitor C2.

The commutation command 56 is, as described later,
When the output voltage of the harmonic elimination circuit 13 becomes higher than the output voltage of the sampling circuit 5 amplified by the amplification circuit 6, the output is output from the commutation command circuit 9. Therefore, if for some reason a large voltage value is held in the capacitor C2 of the sampling circuit 5, the output voltage of the harmonic elimination circuit 13 cannot be higher than the amplified output voltage of the sampling circuit 5, and the commutation command 56 cannot be generated, and the brushless motor 51 stops.

However, since the resistor R8 is connected in parallel to the capacitor C2 of the sampling circuit 5, the electric charge accumulated in the capacitor C2 is gradually discharged, though slightly, by the resistor R8. The voltage value of C2 also gradually decreases. Therefore, the resistance R8
Is connected in parallel to the capacitor C2, even if a large voltage value is held in the capacitor C2,
The commutation command 56 can always be regenerated, and the brushless motor 51 does not stop.

The resistance value of the resistor R8 is determined by the value of the capacitor C2.
And the lower limit of the commutation frequency of the inverter circuit 3 at the time of startup. That is, when the lower limit value of the commutation frequency at the time of starting is about 2 Hz, a time constant slightly larger than the cycle of 12 Hz, which is six times that of the commutation frequency, is set. The resistance value of R8 and the capacitance of capacitor C2 are determined. In this embodiment, since the capacitance of the capacitor C2 is 0.1 μF,
The resistance value of the resistor R8 is 1 MΩ.

Note that, depending on the type of the operational amplifier OP2 of the amplifier circuit 6, a leakage current (input bias current) may flow from the non-inverting input terminal to the ground. In such a case, the voltage value of the capacitor C2 rises due to the leakage current, that is, the stored commutation target voltage which is the voltage value of the harmonic elimination circuit 13 changes in the rising direction. This makes it impossible to perform a normal commutation operation. However, by connecting the resistor R8 in parallel with the capacitor C2, such a leakage current can flow through the resistor R8, so that the voltage value of the capacitor C2 can be prevented from increasing, and the voltage value of the capacitor C2 always decreases. Therefore, the output voltage of the harmonic elimination circuit 13 can be maintained in the capacitor C2.

The amplifier circuit 6 amplifies the voltage value stored by the sampling circuit 5 and outputs the amplified voltage value to the priority circuit 8. The amplifier circuit 6 includes the operational amplifier OP2 and 10k
A non-inverting amplifier constituted by two resistors R9 and R10 of Ω, and a variable resistor VR1 of 100 kΩ for reducing the output of the non-inverting amplifier to 1 or less, and a slider of the variable resistor VR1 From the end, the commutation target voltage at the time of steady operation is output.

The operational amplifier OP2 of the non-inverting amplifier has a non-inverting input terminal connected to a capacitor C2 which is an output terminal of the sampling circuit 5, and an output terminal of the operational amplifier OP2 having a resistor R9 and a variable resistor having one end grounded. VR1
Is connected. The other end of the resistor R9 is connected to an operational amplifier OP
2 and one end of a resistor R10, and the other end of the resistor R10 is grounded.

The resistance values of the two resistors R9 and R10 of the non-inverting amplifier are both the same 10 kΩ. Therefore, the output of the sampling circuit 5 is supplied to the non-inverting amplifiers OP2 and OP2.
It is amplified approximately twice by R9 and R10. The output of the sampling circuit 5 that has been amplified by a factor of two is output to the variable resistor VR1, and is reduced to one or less by the variable resistor VR1.
Output to the priority circuit 8. In this embodiment, the output of the sampling circuit 5 that has been amplified twice by the non-inverting amplifiers OP2, R9, and R10 is reduced to 0.7 times by the variable resistor VR1. Therefore, the output of the sampling circuit 5 as a whole is amplified by a factor of 1.4.
FIG. 3E shows an output voltage waveform of the amplifier circuit 6.

It should be noted that the variable resistor VR1
By adjusting the position of the slider, the amplification factor of the entire amplification circuit 6 can be changed, so that the amplification factor can be changed in accordance with the use situation. That is, tuning can be performed so that the motor efficiency is most improved in the normal operation region of the brushless motor 51.

The starting compensation circuit 7 includes a brushless motor 51
Is a circuit for outputting a commutation target voltage to the commutation command circuit 9 in place of the amplified output of the sampling circuit 5 so that the brushless motor 51 can generate a sufficient starting torque at the time of starting. . This starting compensation circuit 7
Operates in conjunction with the output of the chopper control circuit 18.
That is, when the duty ratio of the chopper control output from the chopper control circuit 18 is increased from a small value less than the predetermined value to a predetermined value or more, for example, in this embodiment, the duty ratio of the row output is about 3.8. %, The starting compensation circuit 7 outputs the commutation target voltage at the time of starting to the commutation command circuit 9 via the priority circuit 8. The above-mentioned duty ratio of about 3.8% is determined by the voltage division ratio of the resistors R32 (390Ω) and R33 (10 kΩ).

The starting compensation circuit 7 includes a chopper control circuit 18
Is provided with a 100-kΩ resistor R31, and the other end of the resistor R31 is connected to one end of a 0.1 μF capacitor C11 and an inverting input terminal of an operational amplifier OP11. The other end of the capacitor C11 is connected to the 10 volt output of the auxiliary power supply circuit 2. Operational amplifier OP
One non-inverting input terminal of the auxiliary power supply circuit
A 390Ω resistor R32 connected to the volt output and a 10kΩ resistor R33, one end of which is grounded, are connected. The output terminal of the operational amplifier OP11 is connected to the anode of the diode D11 and a 10 μF electrolytic capacitor C1.
2 is connected to the positive terminal. Diode D11
Is connected to the 10 volt output of the auxiliary power supply circuit 2, while the negative terminal of the electrolytic capacitor C12 is
100 kΩ resistor R34 grounded to the circuit, cathode of diode D12 grounded to the anode, and 500 kΩ
It is connected to one end of a variable resistor VR2 of Ω. The other end of the variable resistor VR2 is connected to one end of a 100 kΩ resistor R35, and the other end of the resistor R35 is connected to the anode of a diode D3 which is the input terminal of the priority circuit 8 as the output terminal of the starting compensation circuit 7. I have.

The operation of the starting compensation circuit 7 will now be described with reference to FIGS. The voltage dividing ratio of the variable resistor VR4 of the speed setting circuit 16 is set low (FIG. 4A)
A), when the duty ratio of the row output of the chopper control circuit 18 is less than about 3.8% (FIG. 4B)
A), since the chopper pulse output from the chopper control circuit 18 is absorbed (suppressed) by the capacitor C11 constituting the low-pass filter of the starting compensation circuit 7, the input voltage to the inverting input terminal of the operational amplifier OP11 is equal to the resistance R3.
2 and about 9.6 input to the non-inverting input terminal by R33
It is 2 volts or more (FIG. 4 (c) A). In such a case, the output voltage of the operational amplifier OP11 is 0 volt (FIG. 4D). Therefore, when the duty ratio of the row output of the chopper control circuit 18 is less than about 3.8%,
The output voltage from the starting compensation circuit 7 is 0 volt (FIG. 4 (e) A). In this state, the brushless motor 5
1 is in a stopped state.

In this state, the voltage dividing ratio of the variable resistor VR4 of the speed setting circuit 16 is increased (FIG. 4A), and the duty ratio of the row output of the chopper control circuit 18 is set to about 3.8.
% (B in FIG. 4B), the discharge of the capacitor C11 of the starting compensation circuit 7 cannot follow the charge, and the input voltage to the inverting input terminal of the operational amplifier OP11 becomes about 9.6.
The voltage drops to 2 volts or less (FIG. 4C). As a result, the input voltage to the non-inverting input terminal of the operational amplifier OP11 becomes higher than the input voltage to the inverting input terminal, and the operational amplifier OP1
1 rises from 0 volts to about 8.5 volts (FIG. 4 (d) B). Here, about 8.5 volts is the limit value of the output voltage determined by the characteristics of the operational amplifier (the operational amplifier can output only up to 1.5 volts of the power supply voltage or less due to the characteristics. Is 10 volts, so 10 volts−1.5 volts =
It is 8.5 volts. The value of 1.5 volts naturally depends on the type of the operational amplifier.)

The output voltage of the operational amplifier OP11 is about 8.5
When the voltage reaches volts, a voltage of about 8.5 volts is applied to a differentiating circuit composed of the capacitor C12 and the resistor R34. For this reason, a differential pulse-like voltage wave that gradually decreases as time elapses from a voltage value of slightly less than 8.5 volts by subtracting the voltage drop from the starting compensation circuit 7 through the variable resistor VR2 and the resistor R35. It is output to the priority circuit 8 (FIG. 4 (e) B). Since the capacitance of the capacitor C12 is 10 μF and the resistance of the resistor R34 is 100 kΩ, this voltage wave is generated after one second (10 μF × 100 kΩ = 1).
In s), it is reduced to about 37% of its peak value.

The output voltage of starting compensation circuit 7 output to priority circuit 8 is output to commutation command circuit 9 as a commutation target voltage. Therefore, since the commutation target voltage at the time of starting the brushless motor 51 is set high, at the time of starting the plurality of brushless motors 51, an armature current sufficient to generate a starting torque flows (FIG. 4 (f) B). ), The plurality of brushless motors 51 are started accurately.

On the other hand, if the voltage dividing ratio of the variable resistor VR4 of the speed setting circuit 16 is reduced during the rotation of the brushless motor 51 (FIG. 5A), the brushless brushless motor 51 and the brushless motor decrease in duty ratio of the row output. The effective value of the voltage applied to the motor 51 also decreases, and the brushless motor 51 is decelerated. And the chopper control circuit 1
When the duty ratio of the row output of No. 8 falls below about 3.8% (FIG. 5B), the charging of the capacitor C3 of the starting compensation circuit 7 cannot follow the discharging, and the operational amplifier OP11
The input voltage to the inverting input terminal of FIG. 1 rises to 9.62 volts or more, which is the input voltage to the non-inverting input terminal (FIG. 5C), and the output voltage of the operational amplifier OP11 changes from approximately 8.5 volts to 0 volts. It descends (FIG. 5D). When the output voltage of the operational amplifier OP11 becomes 0 volt, the electric charge stored in the capacitor C12 is changed to the diode D12 and the operational amplifier O11.
It is rapidly discharged through P11 and returns to the initial state.

From this state, the voltage division ratio of the variable resistor VR4 of the speed setting circuit 16 is increased again (FIG. 5A), and the duty ratio of the row output of the chopper control circuit 18 is about 3.
When it exceeds 8% (FIG. 5B), the operational amplifier OP11
, The input voltage to the inverting input terminal drops to 9.62 volts or less (FIG. 5C), and the output voltage of the operational amplifier OP11 rises to about 8.5 volts (FIG. 5D). As a result, until the discharged capacitor C12 is recharged, a voltage pulse in the form of a differential pulse is output again from the starting compensation circuit 7 (FIG. 5 (e)).

When the DC power supply 50 is turned off during the operation of the brushless motor 51, the charge stored in the capacitor C12 is rapidly discharged through the diodes D11 and D12, and returns to the initial state. Therefore, even when the DC power supply 50 is turned on immediately after the power is turned off, the start-up compensation circuit 7 is normally operated, and the brushless motor 5 is operated.
1 can be started smoothly.

As described above, in the starting compensation circuit 7 of the present embodiment, even if the voltage dividing ratio of the variable resistor VR4 of the speed setting circuit 16 is reduced and the plurality of brushless motors 51 being driven stop or rotate at a low speed. , Then the variable resistor V
By increasing the voltage division ratio of R4, a commutation target voltage sufficient for starting the plurality of brushless motors 51 can be output from the start compensation circuit 7. Therefore, even in such a case, the plurality of brushless motors 51 can be started accurately. Thus, the start compensation circuit 7 is configured to operate in conjunction with the speed setting by the variable resistor VR4 of the speed setting circuit 16.

The priority circuit 8 outputs the output of the sampling circuit 5 amplified by the amplifier circuit 6, that is, the commutation target voltage at the time of steady operation, and the output of the starting compensation circuit 7, that is, the commutation target voltage at the time of starting. Is a circuit for outputting the larger output voltage to the commutation command circuit 9, and is constituted by a diode D3. This diode D3
Has its anode connected to the output terminal of the starting compensation circuit 7, its cathode connected to the output terminal of the amplifier circuit 6, and the inverting input terminal of the comparator CP 1 which is one input terminal of the commutation command circuit 9. . Therefore, the higher output voltage of the amplifier circuit 6 and the starting compensation circuit 7 is output to the commutation command circuit 9 as the commutation target voltage by the priority circuit 8.

The commutation command circuit 9 includes a brushless motor 51
Of the commutation command 56 of the counting circuit 11, the sampling circuit 5,
And a circuit for outputting to the zero reset circuit 10. The circuit mainly includes a comparator CP1 and a monostable multivibrator MM1. Comparator CP
1 is connected to the output terminal of the priority circuit 8, while the non-inverting input terminal is connected to the output terminal of the harmonic elimination circuit 13 via the resistor R16. Further, the comparator C
The output terminal of P1 is connected to the input terminal A of the monostable multivibrator MM1.
K, the sampling circuit 5 and the zero reset circuit 10 are connected to the gates of both analog switches AS2 and AS3.

The commutation command circuit 9 includes a diode D4, the anode of which is connected to the output terminal of the sampling timing correction circuit 19, and the cathode of which is connected to one end of a 100 kΩ variable resistor VR3. I have.
The other end of the variable resistor VR3 is connected to one end of a 10 kΩ resistor R15, and the other end of the resistor R15 is connected to one end of a 0.1 μF capacitor C5 and the monostable multivibrator MM1. The other end of the capacitor C5 is also connected to the monostable multivibrator MM1.

In the commutation command circuit 9, the comparator CP1
The output voltage of the harmonic elimination circuit 13 and the priority circuit 8
The magnitude of the output voltage is compared with the magnitude of the output voltage. As a result of the comparison, when the output voltage of the harmonic elimination circuit 13 becomes larger than the output voltage of the priority circuit 8, as shown in FIG. 3F, the high signal 55 is output from the output terminal of the comparator CP1 to the monostable multivibrator MM1. Output to input terminal A. As a result, a one-shot high signal (commutation command 56) is output from the output terminal Q of the monostable multivibrator MM1 to the counting circuit 11, as shown in FIG. The commutation command 56 is also output to the gates of the analog switches AS2 and AS3 of the sampling circuit 5 and the zero reset circuit 10 at the same time.
Is turned on.

The sampling circuit 5 holds the instantaneous output of the harmonic elimination circuit 13 immediately before the analog switch AS2 is turned off. Since the analog switch AS2 is turned on while the high commutation command 56 is output,
The sampling circuit 5 holds the instantaneous output of the harmonic removal circuit 13 at the timing when the commutation command 56 falls. Therefore, the timing of extracting the instantaneous output by the sampling circuit 5 is determined by the pulse width of the commutation command 56.

For this reason, the pulse width of the commutation command 56 is such that the end position of the pulse is located between the first current increasing region 41 and the second current increasing region 42 shown in FIG. Is set to That is, the pulse width of the commutation command 56 is set so that sampling by the sampling circuit 5 is performed in regions other than the first and second current increasing regions 41 and 42.

The reason for this is that the current value of the first current increasing region 41 depends on the difference between the voltage applied to the armature winding of the brushless motor 51 and the speed electromotive force due to the rotation of the motor, and the armature impedance. This is because, in particular, the current increase rate is uniquely determined by the time constant of the armature impedance, and is not the current value and the increase rate determined by the generated torque of the motor. Further, the current value of the second current increasing region 42 is a difference between the voltage applied to the armature winding of the brushless motor 51 and the speed electromotive force due to the rotation of the motor,
This is because the current value is substantially determined by the resistance component in the armature impedance and hardly contributes to the generated torque of the motor.

Therefore, the first and second current increasing regions 4
It is not possible to determine an appropriate commutation timing for maintaining the generated torque according to the load based on the current values of 1, 42. In other words, an appropriate commutation timing can be determined based on current values in regions other than the first and second current increasing regions 41 and 42. Therefore, the first and second current increasing regions 4
The pulse width of the commutation command 56 is set so that the sampling circuit 5 performs extraction in an area other than the areas 1 and 42.

Specifically, the pulse of the commutation command 56 is the first
And the shortest pulse width of the commutation command 56 is 3 to 10 times or more the LR time constant (τ) determined by the armature impedance of the brushless motor 51 so as to end in an area other than the second current increasing areas 41 and 42. Time (3τ to 10τ)
Seconds). At the time of the sample holding operation of the sampling circuit 5, the instantaneous output of the harmonic elimination circuit 13 shows a tendency to be substantially saturated, and a time margin of 95% or more of the final value is considered. Further, the longest pulse width of the commutation command 56 is set to a time (２ / 3 × T seconds) which is ／ times the commutation period (T) when the brushless motor 51 rotates at the highest speed.
This is because the width of the second current increasing region 42 at the time of the highest rotation was set to 1/3 × T by an experiment ((1-1 / 3) × T = 2/3 × T).

As described above, the variable resistor VR
The output voltage of the sample timing correction circuit 19 is applied to the resistor 3 and the resistor R15 via the diode D4.

The sampling time correction circuit 19 changes the pulse width of the commutation command 56 output from the commutation command circuit 9 according to the rotation speed of the brushless motor 51, and changes the sampling time (instantaneous output) (Extraction time) is corrected to an appropriate timing.
The sample timing correction circuit 19 includes a comparator CP4,
It comprises a 1 kΩ pull-up resistor R43 connected to the output terminal of the comparator CP4. The non-inverting input terminal of the comparator CP4 is connected to the output terminal of the speed detection circuit 15, and the inverting input terminal is connected to the output terminal of the sawtooth wave generation circuit 14. The output terminal of the comparator CP4 is connected to the anode of the diode D4 of the commutation command circuit 9. Therefore, as shown in FIG. 6, the output voltage 6 of the speed detection circuit 15 is output from the sampling time correction circuit 19.
When 1 is higher than the output voltage 62 of the sawtooth wave generation circuit 14, a voltage of 10 volts is output. Conversely, when the output voltage 61 of the speed detection circuit 15 is lower than the output voltage 62 of the sawtooth wave generation circuit 14, 0 volt is output. Is output.

As will be described later, the speed detection circuit 15 outputs a voltage 61 corresponding to the rotation speed of the brushless motor 51.
That is, a high voltage is output when the brushless motor 51 is rotating at a high speed, and a low voltage is output when the brushless motor 51 is rotating at a low speed. On the other hand, the sawtooth wave generation circuit 14
A sawtooth voltage 62 that changes at a constant cycle of about 20 kHz is output. Therefore, the output voltage of the sample timing correction circuit 19 is a rectangular wave whose duty ratio changes according to the output voltage of the speed detection circuit 15. As shown in FIG. 6, the duty ratio of the rectangular wave increases as the rotation speed of the brushless motor 51 increases, and decreases as the rotation speed of the brushless motor 51 decreases. Therefore, the effective value of the voltage output from the sampling timing correction circuit 19 and applied to the variable resistor VR3 and the resistor R15 via the diode D4 changes according to the duty ratio of the rectangular wave.

The pulse width of the commutation command 56 output from the monostable multivibrator MM1 decreases as the voltage value applied to the variable resistor VR3 and the resistor R15 increases, and conversely, decreases as the applied voltage value decreases. become longer.
Therefore, when the rotation speed of the brushless motor 51 increases, the duty ratio of the rectangular wave output from the sampling timing correction circuit 19 increases, the effective value of the voltage applied to the variable resistor VR3 increases, and the commutation command The pulse width of 56 becomes shorter. Conversely, when the rotation speed of the brushless motor 51 decreases, the duty ratio of the rectangular wave output from the sampling timing correction circuit 19 decreases, and the variable resistance V
The effective value of the voltage applied to R3 decreases, and the pulse width of commutation command 56 also increases. In this way, the sampling timing correction circuit 19 follows the rotation speed of the brushless motor 51, the pulse width of the commutation command 56 is increased or decreased, and the instantaneous output extraction timing by the sampling circuit 5 is automatically corrected to an appropriate position. Because Therefore, commutation command 5
6, the degree of freedom of the setting range of the pulse width is increased, and the setting can be easily performed. It is most preferable that the pulse width of the commutation command 56 be set to be 倍 times (１ ／ T) of the commutation period (T) when the brushless motor 51 rotates at the highest speed.

The zero reset circuit 10 includes a commutation command circuit 9
For each commutation command 56 output from the
Is a circuit for artificially resetting the output voltage to 0 volts, and includes a resistor R16 of 10 kΩ, a capacitor C6 of 180 pF, and an analog switch AS3. One end of the resistor R16 is connected to the output end of the harmonic elimination circuit 13, and the other end of the resistor R16 is connected to one end of a capacitor C6 that is grounded to form an RC low-pass filter. With this RC low pass filter,
In addition to electrostatic transfer (induction) noise and electromagnetic noise generated by the chopper control, harmonic components that cannot be completely removed by the harmonic removal circuit 13 are further removed.

The other end of the resistor R16, that is, the output end of the RC low-pass filter is connected to the analog switch A.
It is connected to one channel terminal of S3 and one input terminal of the commutation command circuit 9 which is a non-inverting input terminal of the comparator CP1. The other channel terminal of the analog switch AS3 is grounded, and the gate of the analog switch AS3 is connected to the output terminal of the commutation command circuit 9. For this reason, the high commutation command 56 from the commutation command circuit 9
Is output, the analog switch AS3 is turned on by the commutation command 56, the non-inverting input terminal of the comparator CP1 of the commutation command circuit 9 is grounded, and the voltage is reset to 0 volt.

The counting circuit 11 counts each time the commutation command 56 output from the commutation command circuit 9 rises.
It comprises a binary counter CT (TC4017 and clear circuit). The output terminal of the commutation command circuit 9 is connected to the input terminal CK of the counter CT, and the output terminals 0 to 5 of the counter CT are connected to the respective OR gates ORu to Ou of the distribution circuit 12.
The output terminals 6 to 9 of the counter CT are connected to a diode D
The terminals are connected to the clear terminal CLR through 5 to D8, respectively. The clear terminal CLR is connected to a capacitor C7 for noise prevention and a pull-down resistor R17 whose other end is grounded to the circuit. When a rising signal is input from the commutation command circuit 9 to the input terminal CK of the counter CT, the output terminal 0, the output terminal 1,...
A high signal is output from the counter CT in the order of the output terminal 5 and the output terminal 0.

The distribution circuit 12 is a circuit for distributing the output from the counting circuit 11 to the inverter circuit 3 and outputting the same. The distribution circuit 12 includes six OR gates ORu to ORz and three inverters Iu to Iw. I have. Inverters Iu to I
w is an open collector type NPN type digital transistor whose emitter terminal is grounded to a circuit, and has a high withstand voltage. It should be noted that each of the inverters Iu to Iw is replaced with a digital transistor, and the source terminal is connected to a circuit grounded N.
-It may be constituted by a MOS field effect transistor. Moreover, you may comprise using a photocoupler etc. as needed.

The input terminal of the OR gate ORu of the distribution circuit 12 is connected to the output terminals 0 and 1 of the counter CT, and the output terminal is connected to the input terminal of the inverter Iu. The input terminal of the OR gate ORv is connected to the output terminals 2 and 3 of the counter CT, and the output terminal is connected to the input terminal of the inverter Iv. The input terminal of the OR gate ORw is a counter C
It is connected to the output terminals 4 and 5 of T, and its output terminal is connected to the input terminal of the inverter Iw. The input terminal of the OR gate ORx is connected to the output terminals 3 and 4 of the counter CT, the input terminal of the OR gate ORy is connected to the output terminals 5 and 0 of the counter CT, and the input terminal of the OR gate ORz is connected to the counter C
It is connected to the output terminals 1 and 2 of T. Inverter Iu ~
The output terminals of Iw and the OR gates ORx to ORz are connected to resistors R1u to R1z connected to the gate terminals of the field effect transistors Qu to Qz of the inverter circuit 3. FIG. 7 shows the relationship between the input and output of the distribution circuit 12, and
The three phases (U
(Phase, V-phase, Z-phase).

The speed detection circuit 15 receives the commutation command 56 output from the commutation command circuit 9 and
1 is a circuit for detecting a commutation period of one and detecting the rotation speed of the brushless motor 51 from the commutation period. The detected speed is converted into a voltage value and output to the speed correction circuit 17 and the sample timing correction circuit 19. In addition, an inverted output (Q bar) of the commutation command 56 is input to the speed detection circuit 15 on the circuit. This takes into account the drive capability of the monostable multivibrator MM1 of the commutation command circuit 9.
Therefore, the output terminal Q of the monostable multivibrator MM <b> 1 may be input to the speed detection circuit 15 when there is no problem in the drive capability. That is, the monostable multivibrator MM2 described later may be configured to output a single pulse for each single pulse output operation of the monostable multivibrator MM1.

The speed detecting circuit 15 has a monostable multivibrator MM2. The input terminal A of the monostable multivibrator MM2 is connected to the output terminal Q bar of the monostable multivibrator MM1 of the commutation command circuit 9. ing. The monostable multivibrator MM2 has one end connected to a 10-volt output of the auxiliary power supply circuit 2 and a 50 k output terminal.
The resistor R36 of Ω, the other end of the resistor R36 and the 0.1 μF capacitor C13 connected to the monostable multivibrator MM2 are connected. Further, the output terminal Q of the monostable multivibrator MM2 has a resistance R of 100 kΩ.
The other end of the resistor R37 is connected to a plus terminal of a 10 μF electrolytic capacitor C14 whose minus terminal is grounded to the circuit and an input terminal of an operational amplifier OP12 forming a buffer. Operational amplifier OP
The output terminal 12 is connected to a speed correction circuit 17 and a sample timing correction circuit 19 as an output terminal of the speed detection circuit 15.

Each time the commutation command 56 falls, a high pulse is output from the output terminal Q bar of the monostable multivibrator MM1 of the commutation command circuit 9 (FIG. 8 (b)). A one-shot high pulse 58 is output from the output terminal Q of the monostable multivibrator MM2 of the circuit 15 (FIG. 8C). The high pulse 58 is averaged by an RC averaging circuit including the resistor R37 and the capacitor C14, and the averaged voltage value appears at a connection end between the resistor R37 and the capacitor C14.

Incidentally, the monostable multivibrator MM
Since the resistor R36 and the capacitor C13 connected to 2 are fixed, the width of the high pulse 58 is constant.
The high pulse 58 is output for each commutation command 56.
Therefore, the shorter the generation cycle of the commutation command 56, that is, the higher the rotation speed of the brushless motor 51, the more the capacitor C
The voltage between the terminals 14 becomes higher (B in FIG. 8 (c)).
The longer the generation cycle of the commutation command 56, that is, the lower the rotation speed of the brushless motor 51, the lower the voltage between the terminals of the capacitor C14 (FIG. 8 (c) A). Thus, the rotation speed of the brushless motor 51 is detected as a voltage between terminals of the capacitor C14.

Since the output impedance (R37) of the RC averaging circuit is relatively large at 100 kΩ, the output impedance is reduced via the buffer constituted by the operational amplifier OP12, and the output impedance is reduced to the speed correction circuit 17 and the sample timing correction circuit 19. Output. Therefore, without causing an RC averaging calculation error in the speed detection circuit 15,
The averaging result can be transmitted to a plurality of circuits (speed correction circuit 17 and sample timing correction circuit 19).

The speed setting circuit 16 includes the brushless motor 5
1 is a circuit for starting and stopping, and for setting a rotation speed. The speed setting circuit 16 is connected to the auxiliary power supply circuit 2.
A 2.2 kΩ resistor R41 connected to the volt output, a 560Ω resistor R42 grounded to the circuit, and both resistors R41,
And a variable resistor VR4 of 5 kΩ connected between R42. A target voltage of the rotation speed is output from a slider end of the variable resistor VR4. That is, by changing the position of the slider of the variable resistor VR4, the brushless motor 51 can be started or stopped, and further its rotation speed can be changed.

The slider end of the variable resistor VR4 has a resistance of 10 kΩ.
A first-order delay circuit composed of a resistor R40 and a 10 μF electrolytic capacitor C16 is connected. The negative terminal of the capacitor C16 is grounded, and the positive terminal thereof is connected to the speed correction circuit 17 together with the resistor R40.

Variable resistance V for setting target voltage of rotation speed
If the slider position of R4 is suddenly changed by the user, the current flowing through the brushless motor 51 changes abruptly, so that the commutation timing becomes unstable or the brushless motor 51
In such a case, a problem such as an overcurrent may flow. However, in the speed setting circuit 16, the target voltage is output through the primary delay circuit including the resistor R40 and the capacitor C16. Therefore, even in such a case, the target voltage can be changed gently. The occurrence of points can be avoided. Therefore, even when the position of the slider of the variable resistor VR4 changes abruptly, the rotation speed of the brushless motor 51 can be gradually changed and the brushless motor 51 can be driven smoothly.

The speed correction circuit 17 compares the voltage value of the target speed set by the speed setting circuit 16 with the voltage value of the actual speed detected by the speed detection circuit 15, and determines the operation amount to be corrected by the chopper. This is for outputting to the control circuit 18. The speed correction circuit 17 allows the speed setting circuit 16
The brushless motor 51 can be rotated at the target speed set in the above.

The speed correction circuit 17 has an operational amplifier OP13. The non-inverting input terminal of the operational amplifier OP13 is connected to the output terminal of the speed setting circuit 16, and the inverting input terminal of the operational amplifier OP13 is connected to the output of the speed detecting circuit 15 via a 5 kΩ resistor R38. Each end is connected. The inverting input terminal of the operational amplifier OP13 is connected to a resistor R39 of 50 kΩ and one end of an integrating capacitor C15 of 0.1 μF. The other ends of the resistor R39 and the capacitor C15 are connected to the output terminal of the operational amplifier OP13. Further, the output terminal of the operational amplifier OP13 is connected to the inverting input terminal of the comparator CP3 of the chopper control circuit 18 as the output terminal of the speed correction circuit 17.

The operational amplifier OP13 of the speed correction circuit 17
Constitutes a non-inverting amplifier for the output of the speed setting circuit 16 together with the resistors R38 and R39. Operational amplifier O
Input voltage to the noninverting input of P13, i.e., the output voltage of the speed setting circuit 16 and V _1, whereas, the operational amplifier OP1
3, the voltage at the other end of the resistor R38 connected to the inverting input terminal of
That is, assuming that the output voltage of the speed detection circuit 15 is V ₂ , 2
Since One of the resistors R38, the resistance value of R39 is respectively 5kΩ and 50kohm, the output voltage V _o of the operational amplifier OP13 _{is, V o = V 1 + 50} /5 × (V 1 -V 2) = V 1 +10
(V ₁ −V ₂ ).

The output voltage of the speed correction circuit 17 is output to the inverting input terminal of the comparator CP3 of the chopper control circuit 18. On the other hand, as described later, the comparator CP
The sawtooth wave generating circuit 14 outputs a sawtooth wave oscillating at a constant period to the non-inverting input terminal of No. Therefore, the target voltage V ₁ of the speed setting circuit 16 is higher than the speed detection circuit 15.
In the case of higher than the detection voltage V ₂ is chopper control circuit 1
The duty ratio of the row output of the rectangular wave output from 8 increases, the effective value of the voltage applied to the brushless motor 51 increases, and the rotational speed of the brushless motor 51 is corrected in the upward direction. Conversely, when the target voltage V ₁ of the speed setting circuit 16 is lower than the detection voltage V ₂ of the speed detection circuit 15, the duty ratio of the row output of the rectangular wave output from the chopper control circuit 18 decreases. Thus, the effective value of the voltage applied to the brushless motor 51 is reduced, and the rotation speed of the brushless motor 51 is corrected in the downward direction. In addition, the stability of the control system is achieved by the integration capacitor C15.

The sawtooth wave generating circuit 14 is a circuit for generating a sawtooth wave 62 having a constant frequency (about 20 kHz in the present circuit) (see FIG. 6). The generated sawtooth wave is output to chopper control circuit 18 and sample timing correction circuit 19.

The sawtooth wave generation circuit 14 includes a comparator CP2. A non-inverting input terminal of the comparator CP2 is connected to a resistor R19 of 100 kΩ, a resistor R20 of 220 kΩ, and an anode of a diode D9. . The other end of the resistor R20 is grounded, and the resistor R19
Is connected to the 10 volt output of the auxiliary power supply circuit 2. The cathode of the diode D9 is connected to a resistor R18 of 1 kΩ whose other end is connected to the 10-volt output of the auxiliary power supply circuit 2, an output terminal of the comparator CP2, and an output terminal of 82 kΩ.
And the cathode of the diode D10. The other end of the resistor R21 and the anode of the diode D10 are connected to a 180-pF capacitor C8, the other end of which is grounded, and the inverting input terminal of the comparator CP2. An inverting input terminal of the comparator CP2 is connected to a chopper control circuit 18 and a sample timing correction circuit 19 as an output terminal of the sawtooth wave generation circuit 14. That is, the sawtooth wave 62 of about 20 kHz applied to the inverting input terminal of the comparator CP2 is output to the chopper control circuit 18 and the sample timing correction circuit 19.

The chopper control circuit 18 converts the chopper-shaped rectangular wave into the lower arm transistors Qx to Qx of the inverter circuit 3.
This is a circuit for outputting to Qz to control the brushless motor 51 by chopper control. The brushless motor 5 is controlled by controlling the duty ratio of the rectangular wave output from the chopper control circuit 18, that is, by performing pulse width modulation.
1, the effective voltage applied to the brushless motor 51 is controlled, and the variable speed operation of the brushless motor 51 is performed.

The chopper control circuit 18 has a comparator CP 3, the non-inverting input terminal of which is connected to the output terminal of the sawtooth wave generating circuit 14, and the inverting input terminal of which is connected to the output terminal of the speed correction circuit 17. ing. The output terminal of the comparator CP3 is a 1 kΩ pull-up resistor R25.
And the output terminals of the chopper control circuit 18 are connected to the input terminals of the inverters Ia, Ix to Iz and the input terminal of the starting compensation circuit 7. .

The chopper control circuit 18 outputs a rectangular wave of about 20 kHz, which is the same as the frequency of the sawtooth wave output from the sawtooth wave generation circuit 14. The duty ratio of this rectangular wave is determined by the position of the slider of the variable resistor VR4 of the speed setting circuit 16 and the rotation speed of the brushless motor 51 detected by the speed detection circuit 15. As the duty ratio of the rectangular wave row output increases, the brushless motor 51 rotates at a higher speed.

Next, the operation of the brushless motor drive circuit 1 configured as described above will be described. When a DC voltage of 30 volts is applied from the DC power supply 50, the auxiliary power supply circuit 2
Supplies a stabilized voltage of 10 volts to each circuit. The counting circuit 11 receiving the driving voltage of 10 volts from the auxiliary power supply circuit 2 outputs, for example, “10000” from the output terminals 0 to 5.
A signal “0” is output to the distribution circuit 12. Upon receiving this, the distribution circuit 12 outputs “011010” to the inverter circuit 3 as the output of “uvwxyz” (FIG. 7).
reference). In the inverter circuit 3, the upper arm transistor Qu is turned on by such a signal, and the lower arm transistor Qy is turned on and off based on the chopper-shaped rectangular wave output from the chopper control circuit 18. As a result, an armature current flows from the U-phase to the V-phase of the armature winding of the brushless motor 51, and the plurality of brushless motors 51
Is started. The armature current is accompanied by a substantially triangular pulsation (harmonic component) that increases when the lower arm transistor Qy is on and decreases when the lower arm transistor Qy is off.

The armature currents flowing through the plurality of brushless motors 51 are collectively detected by the shunt resistor Rs of the current detection circuit 4, converted into a voltage, and output to the harmonic elimination circuit 13. The output voltage of the current detection circuit 4 is
The harmonic removal circuit 13 stores the data in the capacitor C1 in synchronization with the output of the chopper control circuit 18 while the lower arm transistor Qy of the inverter circuit 3 is on. By storing the output voltage of the current detection circuit 4 in synchronization with the chopper control in this way, harmonic components due to the chopper control are removed. The output voltage of the current detection circuit 4 stored in the capacitor C1 is amplified by a factor of about 5.7, and further passed through an RC low-pass filter including a resistor R16 and a capacitor C6. Is output to the non-inverting input terminal.

On the other hand, in the starting compensation circuit 7, when the duty ratio of the row output of the rectangular wave output from the chopper control circuit 18 reaches a predetermined value or more (for example, about 3.8% or more) (FIG. 4B). ), The output voltage of the operational amplifier OP11 is 0
It rises sharply from the bolt to about 8.5 volts (Fig. 4 (d)
B). Due to the increase of the output voltage of the operational amplifier OP11, a differentiating circuit constituted by the capacitor C12 and the resistor R34 operates, and a differential pulse-like voltage gradually falling from a voltage value of slightly less than 8.5 volts is output to the priority circuit 8. (FIG. 4 (e) B).

To the priority circuit 8, in addition to the output of the starting compensation circuit 7, the sampling circuit 5 amplified by the amplifier circuit 6
Is also output. However, when the commutation command has not been issued yet, the sampling operation of the sampling circuit 5 is not performed, and the output voltage is 0 volt.
Therefore, the priority circuit 8 gives priority to the output of the starting compensation circuit 7 over the output of the sampling circuit 5 and the commutation command circuit 9
To the inverting input terminal of the comparator CP1.

In the commutation command circuit 9, the comparator CP1
Thus, the output voltage of the harmonic elimination circuit 13 and the priority circuit 8
Is compared with the output voltage of the starting compensation circuit 7 output through As a result of the comparison, the output of the commutation command 56 is on standby until the output voltage of the harmonic elimination circuit 13 becomes higher than the output voltage of the starting compensation circuit 7. While the output of the commutation command 56 is on standby, the same phase of the armature winding (for example, U-phase to V-phase)
Phase), the armature current sufficient to generate the starting torque to the plurality of brushless motors 51 is supplied, and the field rotors of the plurality of brushless motors 51 gradually start rotating. .

The value of the armature current of the brushless motor 51 changes with the rotation of the field. The change in the armature current value is detected by the shunt resistor Rs of the current detection circuit 4 and stored in the harmonic removal circuit 13 in synchronization with the output of the chopper control circuit 18. Stored current detection circuit 4
Is amplified approximately 5.7 times in the harmonic elimination circuit 13 and output to the non-inverting input terminal of the comparator CP1 of the commutation command circuit 9 via the zero reset circuit 10.
As a result, when the output voltage of the harmonic elimination circuit 13 becomes higher than the output voltage of the start compensation circuit 7, the high signal 55 is output from the comparator CP1 of the commutation command circuit 9, and the one-shot multivibrator MM1 outputs the one-shot Flow command 5
6 is output to the counting circuit 11.

The counter CT of the counting circuit 11 to which the commutation command 56 has been input updates the output state of the output terminals 0 to 5 in response to the rise of the pulse of the commutation command 56, and
Output to For example, if the output state of the output terminals 0 to 5 before the commutation command is “100000”, the output is updated to “010000” by the commutation command 56 (see FIG. 7). As a result, each output of “uvwxyz” of the distribution circuit 12 becomes “0”.
11001 ", and the field effect transistors Qu and Qz are turned on in place of the field effect transistors Qu and Qy that were turned on in the inverter circuit 3, and the armature current of the brushless motor 51 flowing from the U phase to the V phase is reduced. It is commutated from the U phase to the W phase.

On the other hand, the commutation command 56 output from the commutation command circuit 9 is output not only to the counting circuit 11 but also to the sampling circuit 5 and the zero reset circuit 10, and the analog switches AS2 and Turn on AS3.

When the analog switch AS3 of the zero reset circuit 10 is turned on, the output voltage of the harmonic elimination circuit 13 is reset to 0 volt. This ensures that the output voltage of the comparator CP1 to the non-inverting input terminal is lower than the output voltage to the inverting input terminal, so that the output of the comparator CP1 of the commutation command circuit 9 is switched from high to low, A pulse 55 is generated (FIG. 3 (f)).
Therefore, the commutation command circuit 9 responding to the single pulse 55
The monostable multivibrator MM1 of the first embodiment has a high output duty ratio of the sample timing correction circuit 15 and a variable resistor VR.
3. When a predetermined time determined by the resistor R15 and the capacitor C5 elapses, the output is switched from high to low, and the state shifts to a state in which the next commutation command 56 is generated.

On the other hand, the sampling circuit 5
6, when the analog switch AS2 is turned on, the analog switch AS2 is connected to the output terminal of the harmonic elimination circuit 13, and the output voltage of the harmonic elimination circuit 13 is applied to the capacitor C2 of the RC low-pass filter including the resistor R7 and the capacitor C2. Is entered. When the commutation command 56 switches from high to low from this state, the analog switch AS2 is turned off.
The voltage value (instantaneous output) of the harmonic elimination circuit 13 immediately before turning off is stored in the capacitor C2. The stored voltage value (instantaneous output) is amplified by about 1.4 times by the amplifier circuit 6 and output to the priority circuit 8. Note that, as described above, the commutation command 56 is transmitted to the first and second current increasing regions 4.
Since it switches from high to low in the middle area of 1,42,
The instantaneous output of the current detection circuit 4 in the intermediate region is extracted by the sampling circuit 5 via the harmonic removal circuit 13.

By the way, as shown in FIG. 4 (e) B, the output voltage of the starting compensation circuit 7 gradually decreases with a lapse of time from a voltage value of slightly less than 8.5 volts with a negative gradient. . On the other hand, since the output voltage of the sampling circuit 5 is the instantaneous value of the armature current detected by the current detection circuit 4, the output voltage gradually (stepwise) increases after the start of the brushless motor 51. That is, the amplified output voltage of the sampling circuit 5 gradually increases discretely with the passage of time after the start of the passage of the armature current.

The priority circuit 8 outputs the larger one of the amplified output voltage of the sampling circuit 5 and the output voltage of the starting compensation circuit 7 to the commutation command circuit 9.
Therefore, the output of the priority circuit 8 switches from the output voltage of the starting compensation circuit 7 to the amplified output voltage of the sampling circuit 5 at a certain point in time. After this switching, the amplified output voltage of the sampling circuit 5 is continuously output to the commutation command circuit 9 as the output voltage of the priority circuit 8 (that is, the commutation target voltage).

The comparator CP1 of the commutation command circuit 9
When the output voltage of the harmonic elimination circuit 13 becomes 1.4 times or more the output voltage of the sampling circuit 5, a high signal 55 is output to the monostable multivibrator MM1 (FIG. 3).
(F)). As a result, a one-shot commutation command 56 is output from the commutation command circuit 9 to the counting circuit 11 (and the sampling circuit 5 and the zero reset circuit 10) (FIG. 3).
(G)) The commutation of the plurality of brushless motors 51 is performed by the counting circuit 11, the distribution circuit 12, and the inverter circuit 3. And by continuing this commutation,
The plurality of brushless motors 51 are rotated.

The commutation command 56 is transmitted from the commutation command circuit 9.
(Q bar output) is output to the speed detection circuit 15 (FIG. 8). In the speed detection circuit 15, a one-shot high pulse 58 having a fixed time width is output from the monostable multivibrator MM2 every time the inverted output rises.
The high pulse 58 is supplied to the resistor R37 and the capacitor C14.
(FIG. 8)
(C)). Since the high pulse 58 is output for each commutation command, the shorter the commutation cycle, that is, the brushless motor 51
The higher the rotation speed of is, the higher the averaged voltage value (the voltage value between the terminals of the capacitor C14). Therefore, the averaged voltage between the terminals of the capacitor C14 is used as the actual speed information of the brushless motor 51 via the buffer OP12 via the speed correction circuit 17 and the sample timing correction circuit 19.
Output (feedback).

[0102] In addition to the voltage value as the actual speed information output from the speed detection circuit 15, the speed correction circuit 17
The voltage value as the target speed information set by the speed setting circuit 16 is output. The speed correction circuit 17 compares and amplifies the two voltage values, and outputs the amplified result to the chopper control circuit 18 as an operation amount. As described above, V ₁ the voltage value of the target speed, when the voltage value of the actual speed is V _2, from the speed correction circuit 17, V _o = V ₁ +10 voltage V _o of (V ₁ -V ₂₎
Is output to the inverting input terminal of the comparator CP3 of the chopper control circuit 18.

Comparator CP of chopper control circuit 18
A sawtooth wave oscillating at a constant period is output from the sawtooth wave generating circuit 14 to the non-inverting input terminal 3. Therefore, the target voltage V ₁ is the speed detection circuit of the speed setting circuit 16 1
When 5 higher than the detection voltage V ₂ of (V _1> V _2), chopper control circuit 18 increases the duty ratio of the low output of the rectangular wave output from the effective voltage applied to the brushless motor 51 Is increased, and the rotation speed is corrected in the upward direction. Conversely, if the target voltage V ₁ of the speed setting circuit 16 is lower than the detection voltage V ₂ of the speed detection circuit 15 (V ₁ <V ₂ ), the duty of the rectangular wave row output output from the chopper control circuit 18 The ratio becomes smaller, the effective value of the voltage applied to the brushless motor 51 decreases,
The rotation speed is corrected in the downward direction. As described above, the actual rotation speeds of the plurality of brushless motors 51 are fed back and corrected so as to match the target speed.

As described above, the brushless motor 5
When the armature current 1 becomes 1.4 times or more the instantaneous value held by the sampling circuit 5, a commutation command 56 is output. Since the extraction by the sampling circuit 5 is performed in the area between the first and second current increasing areas 41 and 42, the commutation command 56 is output in the second current increasing area 42, and the brushless motor 51 commutation is performed. Therefore, the brushless motor drive circuit 1 can smoothly drive the plurality of brushless motors 51 without using a rotor magnetic pole position sensor such as a Hall element or a shaft encoder.

In particular, in the motor drive circuit 1 of the present embodiment,
The actual speed information of the brushless motor 51 is fed back, compared with the target speed set by the user, and the effective voltage applied to the brushless motor 51 is changed according to the difference. Therefore, the plurality of brushless motors 51 can be constantly rotated at a speed matching the target.

The effective voltage applied to the brushless motor 51 is changed by pulse width modulation (PWM) control, and chopper control is used to perform the pulse width modulation control. Harmonic components accompany the chopper control, but the harmonic components are not removed by averaging with a low-pass filter but are removed by operating the harmonic removing circuit 13 in synchronization with the chopper control. Therefore, even when the duty ratio of the chopper control is small, the detection can be performed while the armature current is kept at a correct value. be able to. Accordingly, the plurality of brushless motors 51 can be operated at a variable speed in the entire range where the duty ratio is about 3.8% to 100%.

Further, the instantaneous output of the current detection circuit 4 is extracted by the sampling circuit 5 for each commutation operation, and the commutation operation is performed based on the instantaneous value. The commutation timing is quickly adjusted, and an appropriate commutation operation can be performed.

Next, a modification of the first embodiment will be described with reference to the drawings. FIG. 9 shows a brushless motor drive circuit 100 according to the second embodiment. The brushless motor driving circuit 100 according to the second embodiment includes a speed detection circuit 15 for correcting the actual speed to the target speed by feeding back speed information from the brushless motor driving circuit 1 according to the first embodiment. The circuit 17 and the sample timing correction circuit 19 are deleted and slightly modified. In particular, the starting compensation circuit 107, the commutation command circuit 109,
Changes have been made to the PWM chopper control circuit 114. The same portions as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

The start compensation circuit 107 replaces the amplified output of the sampling circuit 5 with a commutation target voltage so that the brushless motor 51 can generate a sufficient start torque when the plurality of brushless motors 51 start. Is output to the commutation command circuit 109. The start compensation circuit 107 operates in conjunction with the PWM chopper control circuit 114. That is, the PWM chopper control circuit 11
When the duty ratio of the chopper control according to 4 is increased from a small value less than a predetermined value to a predetermined value or more, for example,
When the duty ratio is increased from less than 3% to more than 3%,
The commutation target voltage is transferred to the commutation command circuit 109 via the priority circuit 8.
Output to

The starting compensation circuit 107 includes a diode D101 which is cathode-connected to the output terminal of the PWM chopper control circuit 114, and the anode of the diode D101 is connected to the anode of a 9-volt zener diode ZD100. Zener diode ZD10
0 is connected to one end of a capacitor C103 of 0.1 μF and one end of a resistor R111 of 56 kΩ,
101 is connected to the base terminal. The emitter terminal of the transistor Q101 is connected to the other end of the capacitor C103 and the resistor R111, and to the 10 volt output of the auxiliary power supply circuit 2. The collector terminal of the transistor Q101 is connected to a circuit grounded 1 kΩ resistor R112.
Is connected to the plus side terminal of a 10 μF electrolytic capacitor C104, and the minus side terminal of the electrolytic capacitor C104 is connected to a circuit grounded 100 kΩ
3, a cathode of a diode D102 whose anode is grounded, and one end of a variable resistor VR102 of 500 kΩ. The other end of the variable resistor VR102 is 150 kΩ
The other end of the resistor R114 is connected to the anode of the diode D3, which is the input terminal of the priority circuit 8, as the output terminal of the starting compensation circuit 107.

According to the starting compensation circuit 107, the PWM
The voltage dividing ratio of the variable resistor VR104 of the chopper control circuit 114 is reduced to less than a predetermined value (for example, less than 3%), and the plurality of driven brushless motors 51 temporarily stop or rotate at a low speed. And then
When the voltage division ratio of the variable resistor VR 104 is increased again to a predetermined value or more (for example, 3% or more), a commutation target voltage sufficient for starting the brushless motor 51 is output from the start compensation circuit 107. The motor 51 is started properly. Thus, the starting compensation circuit 107
Operate in conjunction with the PWM chopper control circuit 114.

The commutation command circuit 109 is a circuit for outputting a commutation command of the brushless motor 51 not only to the counting circuit 11 but also to the sampling circuit 5 and the zero reset circuit 10. And a stable multivibrator MM100. The inverting input terminal of the comparator CP101 is connected to the output terminal of the priority circuit 8, while the non-inverting input terminal is connected to the output terminal of the harmonic elimination circuit 13 via the resistor R16. The output terminal of the comparator CP101 is connected to the input terminal A of the monostable multivibrator MM100. Both analog switches AS of the zero reset circuit 10
2, AS3.

The commutation command circuit 109 is provided with a diode D
The diode D104 has an anode connected to an output terminal of the inverter Ia, and a cathode connected to one end of a 100 kΩ variable resistor VR103. The other end of the variable resistor VR103 is a resistor R of 10 kΩ.
115 is connected to one end of the resistor R115.
It is connected to one end of a 1 μF capacitor C105 and the monostable multivibrator MM100. The other end of the capacitor C105 is also connected to the monostable multivibrator MM.
100.

In the commutation command circuit 109, the comparator C
By P101, the magnitude of the output voltage of the harmonic elimination circuit 13 and the magnitude of the output voltage of the priority circuit 8 are compared. As a result of the comparison, when the output voltage of the harmonic elimination circuit 13 becomes higher than the output voltage of the priority circuit 8, a high signal is output from the output terminal of the comparator CP101 to the monostable multivibrator MM100.
Is output to the input terminal A. As a result, a one-shot high signal (commutation command) is output from the output terminal Q of the monostable multivibrator MM100 to the counting circuit 11. This commutation command is also output to the gates of the analog switches AS2 and AS3 of the sampling circuit 5 and the zero reset circuit 10 at the same time.
AS3 is turned on.

As in the case of the first embodiment, the sampling circuit 5 holds the instantaneous output of the harmonic elimination circuit 13 immediately before the analog switch AS2 is turned off. Since the analog switch AS2 is turned on while the high commutation command is being output, the sampling circuit 5 supplies the harmonic removal circuit 13
Will be retained. Therefore, the timing at which the sampling circuit 5 extracts the instantaneous output is determined by the pulse width of the commutation command.

Therefore, the pulse width of the commutation command is such that the end position of the pulse is located between the first current increasing region 41 and the second current increasing region 42 shown in FIG. 1B. It is set as follows. That is, the pulse width of the commutation command is set so that sampling by the sampling circuit 5 is performed in regions other than the first and second current increasing regions 41 and 42.

As described above, the PW is connected to the variable resistor VR103 and the resistor R115 via the diode D104.
The output voltage of the M chopper control circuit 114 is the inverter Ia
And applied. Therefore, the effective value of the applied voltage changes according to the change of the duty ratio of the chopper control. Therefore, the monostable multivibrator MM10
The pulse width of the commutation command output from 0 is variable resistor VR
When the voltage value applied to the resistor 103 and the resistor R115 increases, the voltage decreases, and conversely, when the voltage value decreases, the voltage decreases.

For this reason, when the duty ratio of the pulse output from the PWM chopper control circuit 114 increases and the effective value of the voltage applied to the plurality of brushless motors 51 and the variable resistor VR103 increases, the rotation of the brushless motor 51 increases. As the speed increases, the pulse width of the commutation command also decreases. Conversely, the PWM chopper control circuit 11
4, the duty ratio of the pulse output from the plurality of brushless motors 51 and the variable resistors VR10
When the effective value of the voltage applied to 3 decreases, the rotation speed of brushless motor 51 decreases and the pulse width of the commutation command also increases. As described above, according to the commutation command circuit 109, the pulse width of the commutation command (the timing of extracting the instantaneous output by the sampling circuit 5) automatically follows the variable speed operation by the chopper control. It will be corrected.

The PWM chopper control circuit 114 outputs a chopper-shaped rectangular wave to the lower arm transistors Qx to Qz of the inverter circuit 3 and outputs a plurality of brushless motors 51.
Is a circuit for chopper control. By controlling the duty ratio of the rectangular wave output from the PWM chopper control circuit 114, the effective voltage applied to the brushless motor 51 is controlled, and the variable speed operation of the brushless motor 51 is performed.

The PWM chopper control circuit 114 has a comparator CP102.
A non-inverting input terminal 102 has a resistor R119 of 100 kΩ.
And a resistor R120 of 220 kΩ and a diode D109.
Is connected to the anode. The other end of the resistor R120 is grounded, and the other end of the resistor R119 is connected to the auxiliary power circuit 2
10 volt output. The cathode of the diode D109 has a resistor R118 of 1 kΩ connected at the other end to the 10 volt output of the auxiliary power supply circuit 2, an output terminal of the comparator CP102, and a resistor R121 of 82 kΩ.
And the cathode of the diode D110. The other end of the resistor R121 and the anode of the diode D110 are connected to a 180 pF capacitor C10 grounded to the circuit.
8 and the inverting input terminal of the comparator CP102.

The inverting input terminal of the comparator CP102 is
In addition, it is connected to the non-inverting input terminal of the comparator CP103. On the other hand, the inverting input terminal of the comparator CP103 is connected to the plus terminal of the 10 μF electrolytic capacitor C109 whose minus terminal is grounded to the circuit and the resistor R122 of 10 kΩ. The other end of the resistor R122 is
One end of the variable resistor VR104 is connected to the slider of the 5kΩ variable resistor VR104.
The other end is connected to a 2.2 kΩ resistor R123 connected to the volt output, and the other end is connected to a circuit grounded 560Ω resistor R123.
124. Further, the comparator CP10
3 is connected to the 10 volt output of the auxiliary power supply circuit 2 via a 1 kΩ pull-up resistor R125, and as the output terminal of the PWM chopper control circuit 114, the input terminals of the inverters Ia, Ix to Iz; Start compensation circuit 1
07 is connected to the input terminal.

This PWM chopper control circuit 114 outputs a rectangular wave of about 20 kHz. The duty ratio of the rectangular wave is changed by changing the position of the slider of the variable resistor VR104. Note that the variable resistor VR10
When the position of the slider 4 is suddenly changed, the capacitor C1
By the operation of 09, the duty ratio of the rectangular wave output from the PWM chopper control circuit 114 is gradually changed without sudden change. Therefore, even at the time of such a sudden change in the slider position, the rotation speed of the brushless motor 51 is gradually changed, and the brushless motor 51 is driven smoothly.

FIG. 10 shows a brushless motor drive circuit 200 according to the third embodiment. In the brushless motor driving circuits 1 and 100 of the first and second embodiments, the sampling circuit 5 extracts the instantaneous value of the output voltage of the harmonic elimination circuit 13, and the output voltage of the harmonic elimination circuit 13 is substantially equal to the extracted value. The commutation command is output from the commutation command circuits 9 and 109 when the power becomes 1.4 times. On the other hand, the brushless motor drive circuit 200 of the third embodiment averages the output voltage of the
The commutation command is output from the commutation command circuit 209 when the output voltage of No. 3 becomes approximately 1.4 times the averaged voltage. By configuring the circuit in this manner, the plurality of brushless motors 51 can be driven while reducing the circuit cost. Hereinafter, the second
The same parts as those of the brushless motor drive circuit 100 of the embodiment are denoted by the same reference numerals, and the description thereof will be omitted. Only different parts will be described.

The first reduction circuit 205 includes the harmonic elimination circuit 1
3 is a circuit for reducing the output voltage of No. 3 to 1/2 (divided by 0.5) and outputting it to the commutation command circuit 209.
Two resistors R215 and R216 of 10 kΩ and 180p
And an F capacitor C206. Resistance R
One end of 216 is connected to the output end of the harmonic elimination circuit 13, and the other end is connected to one end of a capacitor C206 that is grounded to form an RC low-pass filter. This RC low-pass filter removes electrostatic transfer (induction) noise and electromagnetic noise generated by chopper control, as well as harmonic components that cannot be completely removed by the harmonic removal circuit 13. The other end of the resistor R216 is connected to the non-inverting input terminal of the comparator CP201 of the commutation command circuit 209 and one end of another resistor R215. The other end of the resistor R215 is grounded, and the resistance values of the two resistors R215 and R216 are both 10 kΩ.
5, R216, and is output to the commutation instruction circuit 209 after being reduced by half.

The averaging circuit 206 includes the harmonic elimination circuit 13
This is a circuit for averaging the output voltage of the second and outputting the averaged voltage to the second reduction circuit 208. A 10 kΩ resistor R213 connected to the output terminal of the harmonic elimination circuit 13;
And an integration circuit with a 100 .mu.F electrolytic capacitor C204 having a minus terminal connected to the other end. The positive terminal of the capacitor C204 is connected to a 1-kΩ resistor R212 grounded to the circuit. The averaging circuit 206 shares a part of the configuration with a start compensation circuit 720 described later, and the circuit cost is reduced in this respect as well.

The start compensating circuit 207 includes an averaging circuit 2 for enabling the plurality of brushless motors 51 to generate a sufficient starting torque when the brushless motor 51 is started.
06, the commutation target voltage is set to the commutation command circuit 2
This is a circuit for outputting to the circuit 09. This starting compensation circuit 2
07 operates in conjunction with the PWM chopper control circuit 114. That is, when the duty ratio of the chopper control by the PWM chopper control circuit 114 is increased from a small value less than a predetermined value to a predetermined value or more, for example, when the duty ratio is increased from less than 3% to 3% or more, The commutation target voltage is output to the commutation command circuit 209.

The starting compensation circuit 207 includes a diode D201 which is cathode-connected to the output terminal of the PWM chopper control circuit 114, and the anode of the diode D201 is connected to the anode of a 9-volt zener diode ZD200. Zener diode ZD20
0 is connected to one end of a capacitor C203 of 0.1 μF and one end of a resistor R211 of 56 kΩ,
201 is connected to the base terminal. The emitter terminal of the transistor Q201 is connected to the other end of the capacitor C203 and the resistor R211 and the 10 volt output of the auxiliary power supply circuit 2. The collector terminal of the transistor Q201 is connected to a circuit grounded 1 kΩ resistor R212.
And the negative terminal of the 100 μF electrolytic capacitor C204. The negative terminal of the electrolytic capacitor C204 is connected to one end of a 100 kΩ variable resistor VR202 whose other end is grounded and one end of a 10 kΩ resistor R213. Have been.

The variable resistor VR 202 is connected to the starting compensation circuit 207
While itself forms an averaging circuit 206
And a second reduction circuit 208 for reducing the output voltage of the starting compensation circuit 207. The slider end of the variable resistor VR202 is connected to the inverting input terminal of the comparator CP201 of the commutation command circuit 209 as the output terminal of the second reduction circuit 208. As described above, the start compensation circuit 207 includes the second reduction circuit 208 and shares a part (C204, R212) of the averaging circuit 206, so that the circuit cost is reduced accordingly. be able to.

By adjusting the position of the slider of the variable resistor VR202, the reduction rate of the output voltage of the averaging circuit 206 and the starting compensation circuit 207 can be changed.
Therefore, it is a matter of course that the brushless motor drive circuit 200 is tuned by adjusting the position of the slider in accordance with the use condition, that is, so as to maximize the motor efficiency in the normal operation region of the brushless motor 51. You can do it. In the present embodiment, the averaging circuit 206 and the starting compensation circuit 2
The position of the slider of the variable resistor VR202 is adjusted so that the output voltage of the variable resistor 07 is reduced (divided) by 0.7 times.

The commutation command circuit 209 is a circuit for outputting a commutation command of the brushless motor 51 to the counting circuit 11 and the zero reset circuit 210. The commutation command circuit 209 includes a comparator CP201, a monostable multivibrator MM200, and a 0.1 μF capacitor for setting a pulse width of a one-shot pulse (commutation command) output from the monostable multivibrator MM200. C205 and a variable resistor VR203 of 100 kΩ. The non-inverting input terminal of the comparator CP201 is connected to the output terminal of the first reduction circuit 205, and the inverting input terminal is the variable resistor VR20 which is the output terminal of the second reduction circuit 208.
2 is connected to the end of the slider. Further, the comparator C
The output terminal of P201 is a monostable multivibrator MM20.
0 is connected to the input terminal A, and the monostable multivibrator M
The output terminal Q of M200 is connected to the input terminal CK of the counting circuit 11,
Analog switch AS203 of zero reset circuit 210
Connected to the gate.

In the commutation command circuit 209, the comparator C
By P201, the magnitudes of the output voltage of the first reduction circuit 205 and the output voltage of the second reduction circuit 208 are compared. As a result of the comparison, when the output voltage of the first reduction circuit 205 becomes higher than the output voltage of the second reduction circuit 208, the comparator C
A high signal is output from the output terminal of P201 to the input terminal A of the monostable multivibrator MM200. As a result, a one-shot high signal (commutation command) is output from the output terminal Q of the monostable multivibrator MM200 to the counting circuit 11. This commutation command is transmitted to the zero reset circuit 2
The signal is also output to the gate of the ten analog switches AS203, and while high, the analog switches AS203 are turned on.

The zero reset circuit 210 is provided for each commutation command output from the commutation command circuit 209.
5 is a circuit for artificially resetting the output voltage at 0 to 0 volt, and is constituted by an analog switch AS203. One channel terminal of the analog switch AS203 is connected to the output terminal of the first reduction circuit 205 and the commutation command circuit 20.
9 of the comparator CP201. On the other hand, the other channel terminal of the analog switch AS203 is grounded, and the gate of the analog switch AS203 is connected to the output terminal of the commutation command circuit 209. Therefore, when a high commutation command is output from the commutation command circuit 209, the analog switch AS203 is turned on by the commutation command, and the output voltage of the first reduction circuit 205 is reset to 0 volts.

FIGS. 11 and 12 show modified examples of the distribution circuit. As described in the section of the prior art, conventionally, the commutation timing of the motor is determined by focusing on the correlation between the speed electromotive force generated in the armature winding of the rotating motor and the position of the field. Brushless motor 51
The three-phase armature winding could not be energized by 180 degrees. However, the brushless motor drive circuits 1, 100, and 200 of the present embodiment focus on changes in the armature current,
Since the plurality of brushless motors 51 are driven sensorlessly, it is possible to energize 180 degrees. By performing the 180-degree energization instead of the 120-degree energization, the rotation speed and output of the brushless motor 51 can be improved.

Therefore, FIG. 11 shows a circuit diagram of the distribution circuit 30 in the case where 180-degree conduction is performed, and FIG.
The relationship of the direction of the current flowing through the armature winding of the brushless motor 51 at each output of the distribution circuit 30 is shown. The resistance value of each resistor in the distribution circuit 30 of FIG.
Each was 10 kΩ, and the capacitance of each capacitor was 1000 pF. Also, the distribution circuit is not fixed to 120-degree conduction or 180-degree conduction, but the output of the distribution circuit can be switched between 120-degree conduction and 180-degree conduction in accordance with the driving state of the brushless motor 51. May be configured. Such a configuration can be realized very easily by a microcomputer.

The present invention has been described based on the embodiments. However, the present invention is not limited to the above embodiments, and various improvements and modifications can be made without departing from the gist of the present invention. Can easily be inferred.

For example, in the brushless motor drive circuits 100 and 200 of the second and third embodiments, the effective voltage value applied to the brushless motor 51 is changed by the PWM chopper control circuit 114, and the variable speed of the plurality of brushless motors 51 is changed. It was configured to be able to drive. However, in order to reduce the circuit cost, the PWM chopper control circuit 11
4 may be deleted to form a brushless motor drive circuit. In such a case, the harmonic elimination circuit 13 and the chopper drivers Ia, Ix to Iz can be eliminated together with the PWM chopper control circuit 114, and in addition, the starting compensation which is operated in conjunction with the PWM chopper control circuit 114 Since the circuits 107 and 207 can be simplified so as to operate only when the power is turned on, the circuit cost can be reduced in this respect as well.

The brushless motor driving circuits 1 and 10
At 0 and 200, the shunt resistor Rs constituting the current detection circuit 4 is inserted into the ground line of the DC link,
The configuration is such that armature currents in all three phases are detected by one shunt resistor Rs. However, if the current detection circuit can detect the armature current, it may be provided at a position other than the ground line of the DC link. The current detection circuits may be separately provided.

In the brushless motor driving circuits 1 and 100 of the first and second embodiments, the detection of the instantaneous output of the harmonic elimination circuit 13 by the sampling circuit 5 is performed in order to quickly respond to a sudden change in load torque. Everything was done. But,
The present invention is not limited to this, and the instantaneous output of the harmonic elimination circuit 13 may be detected once for each of a plurality of commutation commands. In the brushless motor 51 provided with the three-phase armature winding as in the present embodiment, such detection may be performed once every three or six commutation instructions.

In this embodiment, in order to reduce power consumption,
Lower arm transistors Qx to Q for which chopper control is performed
A field-effect transistor was used not only for z but also for the upper arm transistors Qu to Qw. However, the upper arm transistors Qu to Q in which chopper control is not performed
As for w, since high-speed operation is not required, a junction PNP transistor may be used instead of a field-effect transistor in order to reduce the cost of the circuit and improve the availability of parts. Also, instead of the lower arm transistors Qx to Qz, the upper arm transistor Qu
Alternatively, a configuration may be adopted in which chopper control is performed with Qw. Further, the chopper control may be performed by both the upper and lower arm transistors Qu to Qz.

A principle configuration similar to that of the present embodiment may be configured by using a combination of an A / D converter and a microcomputer or a digital signal processor, or using a microcomputer and software having an A / D converter.

[0141]

According to the brushless motor drive circuit according to the first aspect, the current detection circuit causes the armature current of the plurality of brushless motors to be at least one for each energized phase.
Collectively Ru is detected is converted to a voltage to. Based on the detected voltage, a plurality of brushless
Of the current flowing through the armature winding of the motor
Arrival of the second current increase region in the flow cycle is detected,
A commutation command is output at the timing when the second current increase region arrives, and commutation of a plurality of brushless motors is performed. Therefore, according to such a brushless motor drive circuit, there is an effect that a plurality of brushless motors can be rotated (driven) without a sensor.

According to the brushless motor drive circuit of the second aspect, in addition to the effect of the brushless motor drive circuit of the first aspect, the output voltage of the current detection circuit is averaged by the averaging circuit. This is compared with the output voltage of the averaging circuit. As a result of the comparison, when the output voltage of the current detection circuit becomes a predetermined multiple of the output voltage of the averaging circuit, a commutation command is output from the commutation command output circuit, and commutation of the plurality of brushless motors is performed. Since the commutation timing is determined simply by averaging the output voltage of the current detection circuit, the cost of the brushless motor drive circuit can be reduced.

According to the brushless motor driving circuit of the third aspect, in addition to the effect of the brushless motor driving circuit of the first aspect, an instantaneous output of the current detection circuit is extracted by the sampling circuit, and based on the extracted value. , A commutation command is output. Therefore, even when the load torque suddenly changes, the sudden change is instantaneously extracted by the sampling circuit, so that the generation timing of the commutation command is quickly adjusted. Therefore, even in an environment where the load torque changes suddenly,
The commutation operation can be performed at an appropriate timing, and there is an effect that the brushless motor can be driven stably.

According to the brushless motor driving circuit of the fourth aspect, in addition to the effect of the brushless motor driving circuit of the third aspect, extraction of the instantaneous output by the sampling circuit is performed for each commutation operation. Therefore, there is an effect that the generation timing of the commutation command can be more quickly adjusted when the load torque suddenly changes.

According to the brushless motor driving circuit according to the fifth aspect, in addition to the effect of the brushless motor driving circuit according to the third or fourth aspect, the instantaneous output by the sampling circuit is extracted by the first (armature). Since the operation is performed after the current increasing region and before the second (armature) current increasing region, the sampling circuit can extract the instantaneous output of the armature current that directly contributes to the torque generated by the brushless motor. Therefore, by generating a commutation command based on this instantaneous output, the commutation operation can be performed at an appropriate timing, and there is an effect that the brushless motor can be driven stably.

According to the brushless motor drive circuit of the sixth aspect, in addition to the effects of the brushless motor drive circuit of the first aspect, the application of the drive voltage to the brushless motor is performed by a chopper control circuit. The effective voltage applied to the brushless motor can be varied by changing the duty ratio of the chopper control. Since the duty ratio of the chopper control can be changed by the speed changing circuit, there is an effect that the brushless motor can be driven at a variable speed without the sensor by operating the speed changing circuit. In addition, the harmonic elimination circuit stores the output voltage of the current detection circuit in synchronization with the ON operation of the switching element of the inverter circuit by the chopper control circuit, so that harmonic components accompanying the chopper control are eliminated and converted to a voltage. The detected armature current can be detected. Since the commutation command is output based on the output voltage of the harmonic elimination circuit, the commutation operation can be performed at an appropriate timing without being affected by the chopper control, and the brushless motor is driven without a sensor. There is an effect that can be.

According to the brushless motor drive circuit of the seventh aspect, in addition to the effect of the brushless motor drive circuit of the sixth aspect, the actual speed of the brushless motor is detected by the speed detection circuit based on the commutation command. Is fed back to the speed correction circuit. The target speed of the brushless motor is set in a speed change circuit, and this target speed is also output to the speed correction circuit. In the speed correction circuit,
The duty ratio of the chopper control by the chopper control circuit is changed based on the two speeds so that the actual speed of the brushless motor matches the target speed. Therefore, there is an effect that the brushless motor can be driven at a desired speed (target speed).

According to the brushless motor driving circuit according to the eighth aspect, in addition to the effects of the brushless motor driving circuit according to any one of the second to seventh aspects, when starting the brushless motor, the starting torque of the plurality of brushless motors is increased. Is output from the start compensation circuit to the commutation command output circuit. Therefore, even when a plurality of brushless motors are started, a sufficient armature current can be supplied to generate a starting torque, so that the plurality of brushless motors can be started accurately.

According to the brushless motor drive circuit of the ninth aspect, in addition to the effect of the brushless motor drive circuit of the sixth or seventh aspect, the ON duty ratio of the chopper control circuit is reduced to less than a predetermined value. Even if the plurality of brushless motors are stopped or rotated at a low speed, thereafter, when the ON duty ratio is increased to a predetermined value or more, the start compensation circuit to the commutation command output circuit
A voltage sufficient to generate the starting torque is output. Therefore, even at the time of restart after the ON duty ratio of the chopper control is reduced to a value less than the predetermined value, a sufficient armature current can be supplied to generate the starting torque. There is an effect that it can be restarted.

According to the brushless motor driving circuit of the tenth aspect, in addition to the effect of the brushless motor driving circuit of the first aspect, the commutation command is
This signal is output when the output voltage of the current detection circuit or the harmonic elimination circuit becomes a predetermined multiple of the output voltage of the averaging circuit or the sampling circuit. By the zero reset circuit, the output voltage of the current detection circuit or the harmonic elimination circuit is virtually reset to approximately zero volts for each commutation command, and is made smaller than the output voltage of the averaging circuit or the sampling circuit. Therefore, even in the case of a small no-load of the armature current, the zero point can be clearly defined and the commutation command can be reset without fail. Thus, there is an effect that stable sensorless operation can be realized.

[Brief description of the drawings]

1A is a diagram showing a current waveform flowing in one phase of an armature winding of a brushless motor, and FIG.
FIG. 3 is an enlarged view of one block of the current waveform of FIG.

FIG. 2 is a circuit diagram of a brushless motor drive circuit according to one embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between output voltage waveforms of each circuit during a steady operation of the brushless motor. (A)
It is the figure which showed the output voltage waveform of the PWM chopper control circuit, (b) was the figure which showed the ON operation | movement of each transistor of the inverter circuit, (c) showed the output voltage waveform of the current detection circuit. It is a figure, (d) is a figure showing the output voltage waveform of the harmonic elimination circuit, (e) is a figure showing the output voltage waveform of the amplifier circuit, (f) is a commutation command FIG. 3 is a diagram showing an output voltage waveform of a comparator of the circuit;
(G) is a diagram showing an output voltage waveform of the commutation command circuit.

FIG. 4 is a diagram showing a relationship between a voltage dividing ratio of a variable resistor of a speed setting circuit at the time of starting a brushless motor and an output voltage waveform of each circuit. (A) is a figure which shows the mode of change of the voltage division ratio of the variable resistor of a speed setting circuit, (b)
FIG. 3 is a partially enlarged view of an output voltage waveform of a PWM chopper control circuit, and FIG. 3C is a view illustrating a voltage waveform input to an operational amplifier of a start compensation circuit;
(D) is a diagram showing an output voltage waveform of the operational amplifier of the start compensation circuit, (e) is a diagram showing an output voltage waveform of the start compensation circuit, and (f) is an output of the current detection circuit. FIG. 3 is a diagram illustrating a voltage waveform.

FIG. 5 is a diagram illustrating a relationship between a voltage dividing ratio of a variable resistor of a speed setting circuit and an output voltage waveform of each circuit when the brushless motor is driven from a stop to a stop and from a stop to a start. (A) is a diagram showing a state of a change in a voltage dividing ratio of a variable resistor of a speed setting circuit, and (b) is a diagram showing a partially enlarged output voltage waveform of a PWM chopper control circuit. , (C) is a diagram showing a voltage waveform input to the operational amplifier of the starting compensation circuit, (d) is a diagram showing an output voltage waveform of the operational amplifier of the starting compensation circuit,
(E) is a diagram showing an output voltage waveform of the starting compensation circuit, and (f) is a diagram showing an output voltage waveform of the current detection circuit.

FIG. 6 is a diagram showing a relationship between output voltage waveforms of a speed detection circuit, a sawtooth wave generation circuit, and a sample timing correction circuit.

FIG. 7 shows the relationship between the output of the counting circuit and the output of the distribution circuit,
FIG. 4 is a diagram illustrating a relationship between directions of current flowing through an armature winding of the brushless motor at that time.

8A is a diagram showing a voltage waveform of a Q output of a monostable multivibrator of a commutation command circuit, and FIG.
FIG. 3 is a diagram showing a voltage waveform of a Q bar output of a monostable multivibrator of a commutation command circuit, and FIG. FIG. 4 is a diagram illustrating a relationship with a voltage.

FIG. 9 is a circuit diagram of a brushless motor drive circuit according to a second embodiment.

FIG. 10 is a circuit diagram of a brushless motor drive circuit according to a third embodiment.

FIG. 11 is a circuit diagram of a distribution circuit that performs a 180-degree conduction, showing a modification of the distribution circuit.

FIG. 12 is a diagram illustrating a relationship between an output of a counting circuit and an output of a distribution circuit that performs 180-degree conduction, and a relationship of a direction of a current flowing through an armature winding of the brushless motor at that time.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 brushless motor drive circuit 2 auxiliary power supply circuit 3 inverter circuit 4 current detection circuit 5 sampling circuit (part of commutation command circuit) 6 amplifier circuit 7 start compensation circuit 8 priority circuit 9 commutation command circuit (one of commutation command circuits) Part, commutation command output circuit) 10 Zero reset circuit 11 Count circuit (part of conduction control circuit) 12, 30 Distribution circuit (part of conduction control circuit) 13 Harmonic elimination circuit 14 Sawtooth wave generation circuit (chopper control circuit) 15) Speed detection circuit 16 Speed setting circuit (speed change circuit) 17 Speed correction circuit 18 Chopper control circuit (part of chopper control circuit) 19 Sample timing correction circuit 41 First increase area of armature current 42 Electric machine Second increase area of the slave current 50 DC power supply 51 Brushless motor 52 Connection circuit 56 Commutation command 100 Brushless motor drive Circuit 107 Start compensation circuit 109 Commutation command circuit (part of commutation command circuit, commutation command output circuit) 114 PWM chopper control circuit (part of chopper control circuit) VR104 Variable resistor (speed change circuit) 200 Brushless motor drive Circuit 205 First reduction circuit (part of commutation instruction circuit) 206 Averaging circuit (part of commutation instruction circuit) 207 Start compensation circuit 208 Second reduction circuit (part of commutation instruction circuit) 209 Commutation instruction Circuit (part of commutation command circuit, commutation command output circuit) 210 Zero reset circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02P 6/04 H02P 7/74

Claims (10)

(57) [Claims] 1. An inverter circuit having a plurality of switching elements for sequentially supplying a DC voltage to a plurality of phase armature windings of a brushless motor, and commutation by turning on or off the plurality of switching elements of the inverter circuit. A brushless motor drive circuit comprising: an energization control circuit that rotates the brushless motor; a connection circuit that connects a plurality of brushless motors to the inverter circuit; and a connection circuit that is connected to the inverter circuit by the connection circuit. A current detection circuit that converts a current flowing through the armature winding of the brushless motor into a voltage at least once for each energized phase and detects the voltage, and based on the detection voltages of the current detection circuit , B
The total value of the current flowing through the armature winding of the
To detect a second current increase region in one commutation cycle.
And a commutation command circuit for outputting a commutation command to the power supply control circuit at the detected timing and commutating the plurality of brushless motors. 2. The circuit according to claim 1, wherein the commutation command circuit includes an averaging circuit for averaging an output of the current detection circuit, and when an output of the current detection circuit becomes a predetermined multiple of an output of the averaging circuit. 2. A brushless motor drive circuit according to claim 1, further comprising: a commutation command output circuit that outputs a commutation command to the power supply control circuit. 3. The commutation command circuit includes: a sampling circuit for extracting an instantaneous output of the current detection circuit; and a current supply circuit when the output of the current detection circuit becomes a predetermined multiple of an extraction value of the sampling circuit. 2. A brushless motor drive circuit according to claim 1, further comprising a commutation command output circuit for outputting a commutation command to a control circuit. 4. The brushless motor drive circuit according to claim 3, wherein the instantaneous output of the current detection circuit is extracted by the sampling circuit every commutation operation by the conduction control circuit. 5. An extraction of the instantaneous output of the current detection circuit by the sampling circuit is performed after the first armature current increase region and before the second armature current increase region. Item 5. A brushless motor drive circuit according to item 3 or 4. 6. A chopper control circuit for turning on or off a switching element of the inverter circuit turned on by the energization control circuit by chopper control, and synchronizing with an on operation of the switching element of the inverter circuit by the chopper control circuit. A harmonic removal circuit that outputs the stored voltage to the commutation command circuit in place of the current detection circuit, and changes an on / off duty ratio by the chopper control circuit. 6. A brushless motor drive circuit according to claim 1, further comprising a speed changing circuit for changing the rotation speed of said plurality of brushless motors. 7. The speed change circuit is for setting a target speed of the plurality of brushless motors, and determines an actual speed of the brushless motor based on a commutation command output from the commutation command circuit. A speed detection circuit for detecting, and a duty ratio of on / off by the chopper control circuit is changed based on an actual speed detected by the speed detection circuit and a target speed set by the speed change circuit. 7. The brushless motor drive circuit according to claim 6, further comprising a speed correction circuit for correcting an actual speed of the motor to a target speed. 8. When the plurality of brushless motors are started, a voltage sufficient for the plurality of brushless motors to generate starting torque is supplied to the commutation command output circuit instead of the averaging circuit or the sampling circuit. A commutation control output circuit, wherein the commutation command output circuit controls the energization control when an output voltage of the current detection circuit or the harmonic elimination circuit becomes a predetermined multiple of an output voltage of the start compensation circuit. 8. The brushless motor driving circuit according to claim 2, wherein the circuit outputs a commutation command to the circuit. 9. A voltage sufficient for the plurality of brushless motors to generate a starting torque each time the chopper control circuit turns on a duty ratio of a switching element of the inverter circuit from a predetermined value to a predetermined value or more. Is provided in place of the averaging circuit or the sampling circuit to the commutation command output circuit. The commutation command output circuit is configured so that the output voltage of the harmonic elimination circuit is the start compensation. 8. The brushless motor drive circuit according to claim 6, wherein a commutation command is output to the energization control circuit when the output voltage of the circuit becomes a predetermined multiple. 10. Every time a commutation command is output from the commutation command circuit to the energization control circuit, the output voltage of the current detection circuit or the harmonic elimination circuit output to the commutation command circuit is reduced to approximately zero volts. 10. The brushless motor drive circuit according to claim 1, further comprising a zero reset circuit for performing a virtual reset.