JP3308680B2 - Drive device for brushless motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor driving apparatus for obtaining a position detection signal based on a terminal voltage of a stator winding.

[0002]

2. Description of the Related Art For example, a brushless motor has been adopted as a drive motor for a compressor of a refrigerator or an air conditioner in applications where the capacity of the compressor is required because of its easy control of rotation speed. In particular, the relative position between the stator winding and the permanent magnet type rotor is induced in the stator winding without using a position sensor such as a Hall element because of the features such as a small number of lead wires. Position sensorless type detection using an induced voltage has been adopted.

A conventional brushless motor driving apparatus of this type will be described with reference to FIGS. First, the overall configuration will be described with reference to FIG. The positive and negative terminals of the DC power supply 1 are connected to input terminals 4 and 5 of a drive circuit 3 via a current detection resistor 2 on the negative terminal side. Incidentally, the negative terminal of the DC power supply 1 is grounded.

A driving circuit 3 as an output means has an input terminal 4,
5, NPN transistors 6 to 8 and 9 to 11 as semiconductor switching elements are connected in a three-phase bridge. The freewheel diodes 12 to 17 are connected in parallel to the transistors 6 to 11, respectively. The common connection point of the transistors 6 and 9 is connected to the output terminal 18, the common connection point of the transistors 7 and 10 is connected to the output terminal 19, and the common connection point of the transistors 8 and 11 is connected to the output terminal 20. I have.

[0005] The brushless motor 21 includes a stator 2 having U, V and W phase stator windings 22U, 22V and 22W.
2 and a permanent magnet type rotor (not shown). One terminal of the stator windings 22U, 22V and 22W is commonly connected, and the other terminals are connected to the output terminals 18, 19 and 20 of the drive circuit 3, respectively.

The voltage dividing circuit 23 serving as detecting means includes a voltage dividing resistor 2
4 to 29, and the stator windings 22U, 22V
And 22W, that is, the output terminal 1 of the drive circuit 3
8, 19 and 20 and ground and the voltage dividing resistors 24 and 2
5, a series circuit of the voltage dividing resistors 26 and 27 and a series circuit of the voltage dividing resistors 28 and 29 are connected. Then, the voltage dividing resistors 24 and 25 and the voltage dividing resistor 26
And 27 and the voltage dividing resistors 28 and 29 are used as detecting terminals 30, 31, and 32, respectively.

Reference voltage generating circuit 3 serving as reference voltage generating means
Reference numeral 3 includes resistors 34 and 35 for voltage division, which are connected between the positive terminal and the negative terminal of the DC power supply 1.
The common connection point of the resistors 34 and 35 is used as a reference terminal 36.

The resistance ratio between the voltage dividing resistors 24, 26 and 28 of the voltage dividing circuit 23 and the voltage dividing resistors 25, 27 and 29 is K
2 (where K is a natural number), and the resistance value ratio between the resistors 34 and 35 of the reference voltage generating circuit 33 is (K + 1): 1.
Is set to

The comparing means 37 comprises three comparators 38, 39 and 40, each of which has a non-inverting input terminal (+) connected to the detection terminals 30, 31 and 32 of the voltage dividing circuit 23,
Each inverting input terminal (-) is commonly connected to the reference terminal 36 of the reference voltage generation circuit 33.

The control device 41 is composed of a microcomputer and its peripheral circuits. For convenience of description, when shown in a block diagram for each function, a main control circuit 42, a voltage command generation circuit 43, a pulse width modulation (PWM) A) a signal generation circuit 44 and an enable signal generation circuit 45;
In the main control circuit 42, three input ports are connected to output terminals of the comparators 38, 39 and 40, and the other two input ports are output terminals of the PWM signal generation circuit 44 and the enable signal generation circuit 45. And six output ports are connected to the bases of the transistors 6, 7, 8, 9, 10, and 11 via a base drive circuit,
The other output port is connected to the input terminal of the voltage command signal generation circuit 43.

Further, in the voltage command signal generation circuit 43, a speed command signal SV is provided to another input terminal, and an output terminal is connected to an input terminal of the PWM signal generation circuit 44. The other output terminal of the PWM signal generation circuit 44 is connected to the input terminal of the enable signal generation circuit 45.

Next, the operation of the above-mentioned conventional configuration will be described with reference to FIGS. While the brushless motor 21 is rotating, the stator windings 22U, 22V
And 22 W terminal voltages UV, VV and WV
3, the detection voltages UVa, VVa and WVa
Are input to the non-inverting input terminals (+) of the comparators 38, 39 and 40. The power supply voltage E of the DC power supply 1 is divided by a reference voltage generation circuit 33 and output as a reference voltage VR.
Is input to the inverting input terminal (−).

The comparators 38, 39 and 40 compare these detection voltages UVa, VVa and WVa with the reference voltage VR to detect zero-cross points of induced voltages induced in the stator windings 22U, 22V and 22W. I do.

Here, the principle of detecting the position detection signal on behalf of the terminal voltage UV will be described. That is, the comparator 38
As shown in FIG. 7A, the terminal voltage UV and the reference voltage VR
By detecting the cross point with (= E / 2), that is, by detecting the zero cross point of the induced voltage induced in the stator winding 22U, as shown in FIG.
Obtain the phase signal DSU. Then, the main control circuit 42 calculates a time corresponding to an electrical angle of 30 degrees from the phase signal DSU, and shifts the phase signal DSU by the calculated time.
As shown in (c), a position detection signal PSU is obtained. The main control circuit 42 performs the same processing for the other terminal voltages VV and WV to obtain two position detection signals.

The main control circuit 42 logically converts these three position detection signals to obtain base signals as six energization timing signals, and provides these to the bases of the transistors 6 to 11 of the drive circuit 3, Sequential transistor 6
To 11 are turned on and off, so that the stator windings 22U,
Electric current is supplied to 22V and 22W to rotate the rotor.

The control device 41 performs pulse width modulation (PWM) control to perform output adjustment based on the speed command signal SV during actual operation. Specifically, the main control circuit 42 detects a speed detection signal DV indicating the actual rotation speed of the brushless motor 21 based on the position detection signal obtained by the calculation, and sends this to the voltage command signal generation circuit 43. give. Then, the voltage command signal generation circuit 43 compares the speed command signal SV and the speed detection signal DV, and provides a PWM duty signal to the PWM signal generation circuit 44 such that the difference between the two becomes zero.

The PWM signal generating circuit 44 outputs a PWM signal having a duty corresponding to the duty signal supplied from the voltage command signal generating circuit 43 and supplies the PWM signal to the main control circuit 42. The main control circuit 42 Drive circuit 3
Since the base signal supplied to the positive transistors 6, 7, and 8 is modulated by the PWM signal, for example, the terminal voltage UV also becomes a pulse-like voltage as shown in FIG. Of the phase signal DSU obtained by the comparison is also pulse-shaped as indicated by DSU 'in FIG. 8B. Accordingly, the phase signal shown in FIG.
As shown in FIG. 7C, the position detection signal PS is obtained from DSU ' .
I can't get U. The same applies to other terminal voltages VV and WV.

Therefore, conventionally, the enable signal generating circuit 45 generates the enable signal SE in synchronization with the PWM signal (pulse signal) as shown in FIG. 8C, and only when the enable signal SE is generated. For example, the configuration is such that comparison between the terminal voltage UV and the reference voltage VR is permitted. Therefore, as shown in FIG. 8D, a continuous phase signal DSU similar to FIG. 7B can be obtained. The same applies to other terminal voltages VV and WV.

[0019]

In the conventional configuration, the PW
When the carrier frequency of M (the frequency of the PWM signal) is increased, the on-period and the off-period of the pulsed terminal voltage UV (VV, WV) are both shortened, and the phase signal DSU '
Also becomes shorter. Therefore, the enable signal SE
The main control circuit 42 that determines the presence or absence of the pulse of the phase signal DSU ′ only when the occurrence of the phase error is required, and a high-speed determination process is required. This makes it difficult to detect the position detection signal.

In the conventional configuration, the terminal voltages UV, VV
And WV generate vibration immediately after rising. It is known that this is caused by the inductance of the stator windings 22U, 22V and 22W and the stray capacitance between the emitter and the collector of the transistor constituting the drive circuit 3.
In this way, for example, as shown in FIG. 9A, assuming that the terminal voltage UV oscillates,
As shown in the figure, the terminal voltage UV 'that does not reach the reference voltage VR.
, The phase signal DSU ′ is output. Therefore, when the enable signal SE shown in FIG. 9C is given, the main control circuit 42 generates the phase signal DSU as shown in FIG.
The phase signal DSU generated as shown by the broken line in (d) is significantly shifted by the time Tz, and the position detection signal obtained based on this is also significantly shifted.

As in such a conventional configuration, it becomes difficult to detect a position detection signal due to high frequency pulse width modulation,
Alternatively, when the detection of the position detection signal is significantly shifted due to the vibration of the terminal voltage, the brushless motor 21 does not operate or the brushless motor 21 vibrates.

The present invention has been made in view of the above circumstances, and has as its object the purpose of the present invention even when the pulse width modulation is performed at a high frequency or when the terminal voltage of the stator windings vibrates. Another object of the present invention is to provide a brushless motor driving device capable of obtaining an accurate position detection signal.

[0023]

According to the present invention, there is provided a brushless motor driving apparatus, comprising: detecting means for detecting terminal voltages of a plurality of phases of stator windings of a brushless motor; reference voltage generating means for generating a reference voltage; Comparison means for outputting a signal by comparing the reference voltage from the reference voltage generation means with the terminal voltage from the detection means; latch means for latching the signal from the comparison means; Control means for obtaining a detection signal and outputting an energization timing signal based on the position detection signal and a pulse width modulation signal for output adjustment; and energizing the stator winding based on the energization timing signal from the control means. Output means for performing the latch operation at a timing when the pulse width modulation signal changes from on to off. Having the features (claim 1).

In this case, it is further preferable that the latch means is configured to perform a latch operation at a timing delayed by a predetermined time from when the pulse width modulation signal changes from on to off (claim 2).

Further, the predetermined time can be set in a range from when the pulse width modulation signal changes from on to off to when the terminal voltage changes from on to off (claim 3).

Preferably, the latch means comprises a D flip-flop.

[0027]

According to the brushless motor driving device of the first aspect, the latch means latches the signal from the comparison means at the falling timing of the pulse width modulation signal from on to off, so that the pulse width modulation is not performed. Even if the operation is performed at a high frequency, a position detection signal can be easily obtained in response to this, and even if a vibration occurs in the terminal voltage of the stator winding, the position can be detected without being affected by the vibration. A signal can be obtained.

According to the brushless motor driving device of the second aspect, the latch means changes the signal from the comparison means for a predetermined time (preferably, the pulse width) from the time when the pulse width modulation signal falls from on to off. It is set in a range from when the modulation signal changes from on to off to when the terminal voltage changes from on to off.- Claim 3) Since the latch is performed at a delayed timing, the pulse width modulation is performed at a high frequency. Even in this case, the position detection signal can be obtained without any influence of the oscillation of the terminal voltage of the stator winding.

According to the brushless motor driving device of the fourth aspect, since the latch means is constituted by the D flip-flop, the structure is simple and a reliable operation can be expected.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. 1 to 3. In this embodiment, the same parts as those of the conventional example shown in FIGS. The description is omitted here, and only different parts will be described.

That is, in FIG. 1, the control device 46 includes a voltage command signal generation circuit 43 and a P
A WM signal generation circuit 44; a latch circuit 47 as a latch means; and a main control circuit 4 as a control means.
8 and a latch timing signal generation circuit 49.

As shown in FIG.
D flip-flops 47U, 47V and 47W. Then, the D flip-flop 47U,
At 47V and 47W, each data terminal D is connected to the output terminals of comparators 38, 39 and 40, each output terminal Q is connected to three input ports of the main control circuit 48, and each clock terminal CK is The output terminal of the latch timing signal generation circuit 49 is commonly connected.

In the main control circuit 48, another input port is connected to the output terminal of the PWM signal generation circuit 44, and six output ports are connected to the transistors 6, 7, 8,.
The bases 9, 9, and 11 are connected via a base drive circuit, and the other output port is connected to the input terminal of the voltage command signal generation circuit 43. The input terminal of the latch timing signal generation circuit 49 is connected to another output terminal of the PWM signal generation circuit 44.

Next, the operation of the present embodiment will be described with reference to FIG. The control device 46 performs pulse width modulation (PWM) control to adjust the output based on the speed command signal SV in the same manner as the conventional control device 41. That is,
Specifically, as described later, the main control circuit 48 controls the brushless motor 2 based on the position detection signal obtained by the calculation.
The speed detection signal DV indicating the actual rotation speed of the motor 1 is detected and supplied to the voltage command signal generation circuit 43. Then, the voltage command signal generation circuit 43 compares the speed command signal SV and the speed detection signal DV, and provides a PWM duty signal to the PWM signal generation circuit 44 such that the difference between the two becomes zero.

The PWM signal generating circuit 44 outputs a PWM signal having a duty corresponding to the duty signal given from the voltage command generating circuit 43 and gives it to the main control circuit 48. The main control circuit 48 Since the base signal supplied to the transistors 6, 7, and 8 on the positive side of the circuit 3 is modulated by the PWM signal PS , for example, the terminal voltage UV also becomes a pulse-like voltage as shown in FIG. The phase signal DSU obtained by comparison with the voltage VR also has a pulse shape as indicated by DSU ′ in FIG.

In this case, the terminal voltage UV oscillates immediately after rising as shown in FIG.
Then, as shown in FIG. 3C, the rise and fall of the terminal voltage UV are delayed by the time Ton with respect to the rise of the PWM signal PS from off to on and the fall from on to off.
And Toff, and the time Te from the rise of the terminal voltage UV to the fall of the PWM signal PS is longer than the oscillation time Ts of the terminal voltage UV (Te> Ts).

Thus, the latch timing signal generating circuit 4
9 outputs the latch timing signal LS at the falling timing of the PWM signal PS from ON to OFF, as shown in FIG. 3D, and the D flip-flops 47U and 47V of the latch circuit 47. And 47W latch the signals from the comparators 38, 39 and 40 when the latch timing signal LS is applied to the clock terminal CK.

Accordingly, even if the phase signal DSU 'from the comparator 38 changes to high as shown in FIG. 3B due to the oscillating voltage of the terminal voltage UV' as shown in FIG. When the D flip-flop 47U of the latch circuit 47 receives the latch timing signal LS at the clock terminal CK, the phase signal DSU 'from the comparator 38 is low, whereby the D flip-flop 47U
Does not output high as the phase signal DSU as shown in FIG.

Thereafter, when the terminal voltage UV becomes equal to or higher than the reference level VR, the D flip-flop 47U outputs the phase signal DSU 'from the comparator 38 when the latch timing signal LS is supplied. D
High is output as SU ′. As a result, FIG.
As shown in (e), a continuous phase signal DSU is output. Then, the main control circuit 48 calculates a time corresponding to the electrical angle of 30 degrees from the phase signal DSU and shifts the phase of the phase signal DSU by the calculated time, whereby the position detection signal similar to that of FIG. Get PSU. The main control circuit 48 performs the same processing for the other terminal voltages VV and WV to obtain two position detection signals.

The main control circuit 48 logically converts these three position detection signals to obtain six base signals as conduction timing signals. These base signals are sequentially replaced with transistors 6 to 11 of the drive circuit 3 by transistors. 6 to 11
Is turned on and off, and the stator windings 22U, 22V and 22W are energized to rotate the rotor.

As described above, in the present embodiment, the latch circuit 47 outputs the phase signal from the comparing means 37 based on the latch timing signal LS output at the falling timing of the PWM signal PS from ON to OFF. Latching is performed to obtain a continuous phase signal, which is supplied to the main control circuit 48. Therefore, even when the PWM control is performed at a high frequency, the main control circuit 48 can reliably obtain the position detection signal in response to the PWM control.

Normally, the time Ts of the oscillating voltage of the stator winding (for example, UV) is equal to the PWM from the rising of the terminal voltage.
Since it is shorter than the time Te until the fall of the signal PS,
The position detection signal can be obtained without being affected by the oscillation of the terminal voltage of the stator winding. In this case, the rising of the phase signal (for example, DSV) from the latch circuit 47 is slightly delayed from the rising of the terminal voltage (for example, UV). However, since this detection deviation is extremely small as compared with the conventional case, the main control is performed. The circuit 48 can reliably obtain the position detection signal.

As described above, a reliable position detection signal can be obtained by the main control circuit 48 both when the PWM control is performed at a high frequency and when the terminal voltage of the stator winding oscillates. Thus, the brushless motor 21 can be reliably driven, and the brushless motor 21 does not vibrate.

Further, since the latch circuit 47 is composed of three D flip-flops 47U to 47W, the configuration is simple and a reliable latch operation can be expected.

FIGS. 4 and 5 show a second embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals, and only the different parts will be described below. That is,
4, the control device 50 includes a latch timing signal generation circuit 51 instead of the latch timing signal generation circuit 49. This latch timing signal 51
As shown in FIG. 5D, the latch timing signal LS is output at a point in time that is delayed by a predetermined time Tα from the point in time when the PWM signal PS falls from on to off. However, the predetermined time Tα is set smaller than the delay time Toff (Tα <Toff). FIG.
(A), (b) and (c) correspond to FIGS. 3 (a), (b) and (c).

Therefore, in the second embodiment, FIG.
As shown in (e), the latch circuit 47 (for example, the D flip-flop 47U) has a predetermined time T longer than that of the first embodiment.
A phase signal (for example, DSU) is output with a delay of α.

According to the second embodiment, the PW
Since there is a delay time Toff from the time when the M signal PS falls from on to off to the time when the terminal voltage (for example, UV) of the stator winding actually falls, the latch circuit 47 of the latch circuit 47 is considered in consideration of the delay time Toff. The latch timing is set to be immediately before the time when the actual terminal voltage falls, so that even if the PWM control is performed at a high frequency, the position detection signal is more surely received without being affected by the oscillation of the terminal voltage. Can be obtained.

It should be noted that the present invention is not limited to the embodiment described above and shown in the drawings, and it is needless to say that the present invention can be appropriately modified and implemented without departing from the scope of the invention.

[0049]

As described above, the present invention has the following effects. According to the brushless motor driving device according to the first aspect, the latch means switches the signal from the comparison means for comparing the terminal voltage of the stator winding with the reference voltage from the ON state to the OFF state of the pulse width modulation signal. , The position detection signal can be obtained easily in response to the pulse width modulation performed at a high frequency, and oscillation occurs in the stator winding terminal voltage. Even in this case, the position detection signal can be reliably obtained without being affected by the vibration, so that the brushless motor can be reliably driven, and no vibration occurs in the brushless motor.

According to the second and third aspects of the present invention, the latch means causes the signal from the comparison means to be delayed by a predetermined time from the time when the pulse width modulation signal falls from on to off. Since the latch configuration is used, even when the pulse width modulation is performed at a high frequency, the position detection signal can be obtained without any influence of the oscillation of the terminal voltage of the stator winding.

According to the fourth aspect of the present invention, since the latch means is constituted by the D flip-flop, the structure is extremely simple and a reliable operation can be expected.

[Brief description of the drawings]

FIG. 1 is an electrical configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a latch circuit.

FIG. 3 is a waveform diagram of each part.

FIG. 4 is an electrical configuration diagram showing a second embodiment of the present invention.

FIG. 5 is a waveform diagram of each part.

FIG. 6 is an electrical configuration diagram showing a conventional example.

FIG. 7 is a diagram illustrating the principle for obtaining a position detection signal.

FIG. 8 is a waveform diagram of each part.

FIG. 9 is an enlarged waveform diagram of each part.

[Explanation of symbols]

In the drawing, 3 is a driving circuit (output means), 21 is a brushless motor, 22 is a stator, 22U to 22W are stator windings, 23 is a voltage dividing circuit (detecting means), 33 is a reference voltage generating circuit (reference voltage). Generating means), 37 is comparing means, 38 to 40 are comparators, 43 is a voltage command signal generating circuit, and 44 is P
WM signal generation circuit, 46 is a control device, 47 is a latch circuit (latch means), 47U to 47W are D flip-flops, 48 is a main control circuit (control means), 49 is a latch timing signal generation circuit, 50 is a control device, Reference numeral 51 denotes a latch timing signal generation circuit.

Claims (4)

(57) [Claims] 1. A detecting means for detecting terminal voltages of a plurality of phases of stator windings of a brushless motor, a reference voltage generating means for generating a reference voltage, a reference voltage from the reference voltage generating means, and A comparison means for outputting a signal by comparing with a terminal voltage of the latch means; a latch means for latching a signal from the comparison means; a position detection signal obtained by a signal from the latch means; Control means for outputting an energization timing signal based on a pulse width modulation signal; and output means for energizing the stator winding based on the energization timing signal from the control means, wherein the latch means comprises: A drive device for a brushless motor, wherein a latch operation is performed at a timing when a pulse width modulation signal changes from on to off. A detecting means for detecting terminal voltages of a plurality of stator windings of the brushless motor; a reference voltage generating means for generating a reference voltage; a reference voltage from the reference voltage generating means; A comparison means for outputting a signal by comparing with a terminal voltage of the latch means; a latch means for latching a signal from the comparison means; a position detection signal obtained by a signal from the latch means; Control means for outputting an energization timing signal based on a pulse width modulation signal; and output means for energizing the stator winding based on the energization timing signal from the control means, wherein the latch means comprises: A brushless motor configured to perform a latch operation at a timing delayed by a predetermined time from when the pulse width modulation signal changes from on to off. Data drive. 3. The apparatus according to claim 2, wherein the predetermined time is set in a range from when the pulse width modulation signal changes from on to off to when the terminal voltage changes from on to off. Drive device for brushless motor. 4. A brushless motor driving apparatus according to claim 1, wherein said latch means is constituted by a D flip-flop.