JPH0140599B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control circuit that detects the rotational speed of a DC motor using a reverse induced voltage of the DC motor and controls the rotational speed to be constant.

Conventionally, a tachometer generator has been used as a rotation speed detection device for an electric motor. Since a tachometer generator was used, the device was expensive, and the configuration of the electric motor had to be changed in order to install the tachometer generator, resulting in an increase in size. Furthermore, in motors with a small rotor inertia, if the inertia of the tachogenerator increases, the motor becomes less responsive, which reduces the effectiveness of the motor with the small inertia.

In order to eliminate these drawbacks, the present invention detects a time period when power cannot be supplied to the motor from the half-wave or full-wave rectified output of an AC power supply due to the reverse induced voltage of the motor, and detects the reverse induced voltage in the time period. By sampling the voltage and holding the reverse induced voltage with a capacitor at other times, the rotational speed of the motor is detected using the reverse induced voltage to obtain an electrical signal proportional to the rotational speed. Performs speed control.

In addition, the output torque is controlled by the output of the armature current detection circuit using a chopper circuit as an armature current corresponding to the reference positive voltage, and the error amplification circuit and the above-mentioned electric signal proportional to the rotation speed are controlled. constant speed control is performed.

Therefore, there is no need for a large capacitor for smoothing the output of the rectifier circuit for driving the motor, and the power supply circuit can be constructed in a small size and at low cost.

Next, the details of the embodiments shown in FIG. 1 and subsequent figures will be explained.

FIG. 1 shows an embodiment of the invention. Symbol 1 is an AC power supply, and symbol 2 is a bridge diode that performs full-wave rectification of the AC voltage of the AC power supply 1. Symbol 3 is a diode, and symbol 4 is a smoothing capacitor.
Symbol 5 is a resistor, and symbol 6 is a Zener diode. Symbol 7 is a semiconductor switching element (for example, a transistor), and symbol 8 is a reverse voltage protection diode of transistor 7. Symbol 9 is a DC motor, and symbol 10 is an armature current detection device (for example, a resistor). Transistor 7, diode 8, motor 9 and resistor 10 are connected in series. Symbol 11 is a freewheel diode, and electric motor 9
and the resistor 10 are connected in parallel. Symbol 12 is a transistor, and symbol 13 is a diode. Symbol 14 is a capacitor, which is connected to the motor 9 via a transistor 12 and a diode 13.
It is connected to the. Symbol 15 is an OP amplifier whose input terminals are connected to both ends of resistor 10. symbol 1
A transistor 6 is controlled by an OP amplifier 15 to control the transistor 12. symbol 1
7 and 18 are resistors, and symbol 19 is a variable resistor.
Symbol 20 is an OP amplifier, which uses the voltage obtained by dividing the output voltage of the capacitor 14 with resistors 17 and 18 as one input, and the output of the variable resistor 19, that is, the voltage of the reference voltage source for controlling the rotation speed, as the other input. There is. Symbol 21 is an OP amplifier, symbols 22, 23,
24 is a resistance. Symbol 25 is a resistance. Symbol 25 is a Schmitt trigger circuit and OP amplifier 21
and resistors 22, 23, and 24. Schmitt trigger circuit 25 is OP amplifier 2
The output of resistor 10 is used as one input, and the output of resistor 10 is used as the other input. Symbol 26 is a transistor. OP amplifier 21 controls transistor 7 via transistor 26.

Next, FIG. 2 will be explained in detail. The vertical axis of the graph is voltage V, and the horizontal axis is time T. curve 27
is the output voltage waveform of the OP amplifier 20. curve 2
8-1, 28-2 are Schmitt trigger circuits 25
The upper slice level and the lower slice level. A curve 29 is the output voltage waveform of the resistor 10.
Curves 30-1 and 30-2 are times when the output of the bridge diode 2 cannot supply power to the motor 9 due to the reverse induced voltage of the motor 9.

Next, the operation shown in FIG. 1 will be explained in detail using FIG. 2. It is assumed that the output of the OP amplifier 20 is set to an arbitrary value. The current flowing through the motor 9 is detected by the resistor 10, and the detected output is sent to the upper slice level curve 2 of the Schmitt trigger circuit 23.
When the voltage rises above 8-1, the Schmitt trigger circuit 25 turns off the transistor 26, and when the transistor 26 turns off, the transistor 7 also turns off.
When the transistor 7 is cut off, the magnetic energy stored in the armature coil of the motor 9 is discharged via the freewheeling diode 11, and the armature current gradually decreases. When the armature current decreases, the resistance 10
As the output voltage of drops and drops beyond the lower slice level curve 28-2 of the Schmitt trigger circuit 25, the Schmitt trigger circuit 25 conducts transistor 26, and when transistor 26 conducts, transistor 7 conducts. . The armature current therefore increases again. This results in a pulsating flow whose ripple width is determined by the hysteresis width of the Schmitt trigger circuit 25.

Therefore, the armature current, ie, the output torque, is regulated by the output of the OP amplifier 20.

In a section where the output voltage of the bridge diode 2, which serves as a rectifier circuit, is lower than the reverse induced voltage of the motor 9 (which is proportional to the rotational speed), the motor 9 is de-energized, so the armature current becomes zero. becomes.

In the above-mentioned period, the output of the OP amplifier 15 rises, making the transistors 16 and 12 conductive. During this time period, since no armature current flows through the motor 9, the terminal voltage of the motor 9 becomes a reverse induced voltage, the reverse induced voltage is sampled, and the capacitor 14 is charged. While the armature current is flowing
The output of OP amplifier 15 drops and transistor 1
6 and 12 are maintained in a cut-off state, and the voltage of the capacitor 14 is held.

Next, constant speed control will be explained in detail. When the variable resistor 19 is set to an arbitrary position, the rotation speed of the electric motor 9 is determined in accordance with the set position of the variable resistor 19. For example, when the rotational speed of the electric motor 9 increases, the reverse induced voltage increases, and when the reverse induced voltage increases, the output of the OP amplifier 20 decreases. Therefore, the armature current of the motor 9 decreases, controlling the increase in the rotational speed of the motor 9. When the rotational speed of the motor 9 decreases, the reverse induced voltage decreases, and when the reverse induced voltage decreases, the OP amplifier 2
0's output increases. Therefore, the armature current of the electric motor 9 increases, suppressing a decrease in the rotational speed of the electric motor 9. Therefore, the OP amplifier 20 functions as an error amplification circuit.

Symbols 30-1 and 30-2 in FIG. 2 indicate the periods in which the armature current becomes zero due to the reverse induced voltage, that is, the time periods in which the armature circuit becomes non-conductive.

Although the control circuit in the case of full-wave rectification of the AC power supply has been described, the object of the present invention can be achieved with a similar circuit in the case of half-wave rectification.

Another embodiment will be described in detail with reference to FIG. Since the same symbols as in FIG. 1 represent the same members and have the same effects, their explanation will be omitted. Symbol 31 is a diode, symbol 32 is a resistor, symbol 33 is a FET
It is. Symbol 34 is a Zener diode, and symbol 35 is a capacitor. Symbol 36 is an OP amplifier. Symbols 37, 38, 39, 40 are resistances
A differential amplifier circuit is configured with the OP amplifier 36,
Connect the output of bridge diode 2 to resistor 32 and FET
The output voltage divided by 33 is input. Reference numeral 42 denotes an OP amplifier, one input of which is a voltage obtained by dividing the output voltage of the capacitor 14 by resistors 17 and 18, and the other input of which is the output of the variable resistor 19.

Next, FIG. 4 will be explained in detail. The same symbols as in FIG. 2 refer to the same members and have the same effects, so a description thereof will be omitted. Symbol 41 is the output voltage waveform of the OP amplifier 36.

The reason for this will be explained next.

The OP amplifier 36 is a linear amplification circuit, and an output voltage proportional to its two inputs is obtained.

The above two inputs of the OP amplifier 36 are FET
(Field Effect Transistor) It is proportional to the voltage drop between the source and drain of 33, that is, the gate input voltage. The gate voltage is the output voltage of the OP amplifier 42.

When the output of the OP amplifier 42 is a predetermined value, the resistance of the FET 33 also becomes a corresponding predetermined value, so the resistor 32 creates a voltage curve 41 proportional to the output voltage of the bridge diode 2. .

Next, the operation of the constant speed control shown in FIG. 3 will be explained in detail using FIG. 4. When the variable resistor 19 is set at an arbitrary position, the rotation speed of the electric motor 9 is determined in accordance with the set position of the variable resistor hole 19. For example, when the rotational speed of the electric motor 9 increases, the reverse induced voltage increases, and when the reverse induced voltage increases, the output of the OP amplifier 42 increases. Therefore, the gate voltage of the FET also increases, and the resistance value between the source and drain decreases. Therefore, the divided voltage output obtained by dividing the output voltage of the bridge diode 2 becomes smaller, and therefore the voltage amplitude of the OP amplifier 36 also becomes smaller. When the output amplitude of the OP amplifier 36 becomes smaller, the armature current of the motor 9 decreases. Therefore, an increase in the rotational speed of the electric motor 9 is suppressed. When the rotational speed of the electric motor 9 decreases, the reverse induced voltage drops, and when the reverse induced voltage drops, the output of the OP amplifier 42 drops. Therefore, the gate voltage of the FET also drops, and the resistance value between the source and drain increases. Therefore, curve 4 which divides the output voltage of bridge diode 2
The divided voltage output indicated by 1 also increases, and the output amplitude of the OP amplifier 36 also increases. As the output amplitude of the OP amplifier 36 increases, the armature current of the motor 9 also increases. Therefore, a decrease in the rotational speed of the electric motor 9 is suppressed.

The armature current control described above will be explained in more detail.

Curves 28-1 and 28-2 in FIG. 4 indicate the upper and lower slice levels of the Schmitt trigger circuit 25.

A curve 29 shows the armature current due to the chopper action of the transistors 26 and 7 turned on and off by the output of the Schmitt trigger circuit 25.
The armature current 29 is a part of a sine wave, unlike the previous embodiment.

The OP amplifier 42 serves as an error amplification circuit and performs constant speed control.

Although the control circuit in the case of full-wave rectification of the AC power supply has been described, the object of the present invention can be achieved with a similar circuit in the case of half-wave rectification. By making the current waveform of the electric motor 9 part of the voltage waveform obtained by half-wave or full-wave rectification of the alternating current voltage using a semiconductor switching element and a freewheel diode, power supply noise can be reduced, and noise, vibration, etc. can be reduced. can be suppressed.

As explained above, the period when power cannot be supplied to the motor due to the reverse induced voltage of the motor is detected from the half-wave or full-wave rectified output of the AC power supply, and the reverse induced voltage is sampled during the above-mentioned time period. By holding the reverse induced voltage with a capacitor during the time period, the rotation speed of the motor can be detected using the reverse induced voltage.This has the effect of allowing the rotation speed of the motor to be detected without the need for additional equipment such as a tachogenerator. There is.

Further, a capacitor for smoothing the output of the bridge diode (rectifier circuit) 2 is not required, which has the effect of making it smaller and cheaper.

Since the transistor 7 is controlled in the saturation region, it has the effect of improving efficiency in the case of a motor with a large output.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of the control circuit of the device of the present invention;
The figure is a graph for explaining the circuit operation of FIG. 1, and FIG. 3 is a circuit diagram of a control circuit according to another embodiment of the present invention.
FIG. 4 shows graphs for explaining the circuit operation of FIG. 3, respectively. 1... AC power supply, 2... Bridge diode,
3, 8, 31... Diode, 4, 35... Capacitor, 5, 10, 17, 18, 22, 23,
24, 32, 37, 38, 39, 40...resistance,
6, 34... Zener diode, 7, 12, 1
6, 26...transistor, 9...motor, 11
...Freewheel diode, 15, 20, 2
1, 36, 42...OP amplifier, 19...Variable resistor, 25...Schmitt trigger circuit, 27...
Output voltage waveform of error amplifier circuit 20, 28-1, 2
8-2... Upper slice level, lower slice level of Schmitt trigger circuit 25, 29... Output voltage waveform of resistor 10, 30-1, 30-2...
Armature current non-conducting time period, 33...FET, 41
...Output voltage waveform of OP amplifier 36.

Claims (1)

[Scope of Claims] 1 A. A rectifier circuit without a smoothing capacitor that performs full-wave rectification of single-phase sinusoidal alternating current; B. A DC motor driven by the output voltage of the rectifier circuit; C. A rectifier circuit connected in series to the DC motor. an armature current detection circuit that detects the armature current by detecting the voltage drop across the resistor; D. a transistor inserted between the positive voltage terminal of the rectifier circuit and the DC motor; A freewheeling diode connected in parallel to the series connection body, and E. Only the reverse induced voltage in the section where the output voltage of the rectifier circuit described above is less than the reverse induced voltage of the DC motor is charged to a capacitor and smoothed, and the charged voltage is rotated. A rotational speed detection circuit that obtains an electrical signal proportional to the speed, F. A reference positive voltage source for commanding the rotational speed, and G. An error amplification circuit that receives the voltage of the reference positive power supply and the output voltage of the rotational speed detection circuit as input. circuit, H. When the output of the rotational speed detection circuit exceeds a set value by the output of the error amplification circuit, the above-mentioned transistor is turned non-conductive, and the armature current through the freewheel diode drops by a predetermined value. 1. A constant speed control circuit for a DC motor, comprising an electric circuit that maintains a set speed by repeating a cycle of making a transistor conductive again. 2. In the claim set forth in item 1, an electric circuit obtains a constant voltage power source from a part of the output of a rectifier circuit using a diode, a capacitor, and a Zener diode, and divides the constant voltage power source by a variable resistor to obtain a reference positive voltage. 1. A constant speed control circuit for a DC motor, characterized by comprising a voltage dividing circuit as a source. 3. In the claim set forth in item 1, an electric circuit obtains a constant voltage power source from a part of the output of a rectifier circuit using a diode, a capacitor, and a Zener diode, and a reference positive voltage source by dividing the constant voltage power source with a resistor. The output voltage of the rectifier circuit described above is applied to a series connection of a FET and a resistor whose gate input is the output of the error amplification circuit, and the output voltage of the rectifier circuit is applied to the FET.
an electric circuit that obtains a voltage signal having a sinusoidal full-wave rectified waveform from a connection point between the and the resistor; and when the output voltage of the rotational speed detection circuit increases beyond the voltage signal, the transistor is turned non-conducting; A constant speed control circuit for a DC motor, comprising an electric circuit that maintains a set speed by repeating a cycle of turning on a transistor again when the armature current flowing through a freewheel diode drops by a predetermined value.