JPH07123775A - Rotor position signal generator for sensorless brushless motor and driver for the same motor - Google Patents

Abstract

PURPOSE:To simplify a circuit without necessity for complicated process using an integration circuit, etc., by comparing phase voltages of armature windings of a sensorless brushless motor with each other, and obtaining a rotor position signal. CONSTITUTION:When a motor 2 starts, phase voltages U, V, W present at armature windings 3u, 2v, 3w are applied to comparators 6a, 6b, 6c through filters 9u, 9v, 9w. The comparators 6a, 6b, 6c obtain differences of output voltages Vu, Vv, Vw, and output voltages V1, Vb, Vc. The voltages Va, Vb, Vc respectively correspond to predetermined angular positions of a rotor 4 to become rotor position signals of the motor 2. A controller 5 applies it to a switching signal generator 54 through contacts 58a, 58b, 58c to generate a switching signal. Since a commutation circuit 1 is controlled by the switching signal, it is ordinarily stably operated at a predetermined synchronizing speed.

Description

Detailed Description of the Invention

The present invention relates to a sensorless brushless motor, and more particularly to a rotor position signal generation circuit for a sensorless brushless motor and a drive circuit for a sensorless brushless motor.

[0002]

2. Description of the Related Art In a conventional brushless motor drive circuit, a rotor position signal used for generating a motor drive signal is obtained from a plurality of Hall sensors provided around the rotor so as to surround it. There was something I did. However, in this case, the wire from the Hall sensor goes out of the motor, which complicates the wiring, and because the Hall sensor is placed around the rotor, miniaturization of the motor is hindered, and the Hall sensor may be damaged if the temperature rises. there were.

From this point of view, in recent years, a sensorless brushless motor has been developed in which a rotor position signal is obtained without using a sensor such as a Hall sensor. One example thereof is disclosed in Japanese Patent Publication No. 58-25038. It is shown. In such a conventional technique, the rotor electromotive force induced in the armature winding is compared with the neutral point voltage to detect the rotor position. Specifically, the signal obtained as a result of the comparison is detected. Through an integrator circuit with the phase and attenuation adjusted appropriately,
The signals thus obtained are compared again to obtain the rotor position signal.

[0004]

In the prior art described in the above Japanese Patent Publication, a complicated process is required by using an integrating circuit and the like, which complicates the circuit, which complicates the assembly and the cost. It became high.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a rotor position signal generation circuit of a sensorless brushless motor and a sensorless brushless motor which can generate a rotor position signal with an inexpensive and simple structure. To provide a driving circuit.

[0006]

SUMMARY OF THE INVENTION According to the present invention, by comparing the phase voltage of each pair of armature windings of a sensorless brushless motor with a comparator, the rotor position signal of the sensorless brushless motor is output from each comparator. Is to get. Further, a filter is connected to each of the armature windings, and a phase voltage obtained from the filter for each pair of the filters is compared by a comparator to obtain a rotor position signal more accurately. Is.

[0007]

In the present invention, the phase voltage of each armature winding is
It is the superimposed voltage of the excitation voltage from the drive circuit and the rotation electromotive force, and the peak value of each phase voltage appears at a predetermined angular position of the rotor, and therefore the voltage difference between the phase voltages of each pair of armature windings. Paying attention to the point that appears at the phase angle position corresponding to the rotor position signal, the rotor position signal of the sensorless brushless motor is obtained by comparing the phase voltage of each pair of armature windings with a comparator. Is. Further, the phase voltage of each armature winding is passed through a filter (low-pass filter) and then compared by a comparator to obtain a rotor position signal more accurately. Therefore, the circuit configuration required to obtain the rotor position signal is only the comparator (and the filter), and the circuit configuration can be simplified, so that the inexpensive rotor position signal generating circuit can be provided.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a rotor position signal generating circuit for a sensorless brushless motor and a drive circuit for a sensorless brushless motor according to the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a circuit diagram showing a configuration of an embodiment of the present invention, and FIG. 2 is a timing chart showing signal waveforms in respective parts of FIG. Although the present embodiment applies the present invention to a three-phase sensorless brushless motor as a typical example, the present invention can be applied to a multi-phase sensorless brushless motor regardless of the number of phases.

In FIG. 1, armature windings 3u, 3v, 3w of the brushless motor 2 have resistors 8u, 8v, 8 respectively.
The capacitors 7u, 7v, and 7w are connected via w to one end, and the other ends of these capacitors are grounded. Each set of these resistors 8u, 8v, 8w and capacitors 7u, 7v, 7w constitutes low pass filters 9u, 9v, 9w, respectively. The comparator 6a is connected to the connection point of the resistor 8u and the capacitor 7u, and the comparator 6b is connected to the resistor 8v and the capacitor 7v.
The comparator 6c is connected to the connection point of the resistor 8w and the capacitor 7w. The comparator 6a compares the voltage at one end of the capacitors 7u and 7w, the comparator 6b compares the voltage at one end of the capacitors 7u and 7v, and the comparator 6c.
Compares the voltages at one ends of the capacitors 7v and 7w. The output voltage signals Va, Vb, Vc of the comparators 6a, 6b, 6c are given to the control circuit 5 as position signals of the rotor.

The control circuit 5 includes a timer 50, a starting rotor position signal generating circuit 52, and a switching signal generating circuit 5.
4, a relay 56 controlled by a timer, a contact 5 responsive to the relay and connected to the switching signal generating circuit 54
It has 8a, 58b and 58c. Under the control of the timer 50, the starting rotor signal generating circuit 52 generates a starting rotor position signal for a predetermined time after starting the motor 2 and generates a switching signal via the relay contacts 58a, 58b, 58c. It is given to the circuit 54. The relay 56 has a contact 58 under the control of the timer 50 for a predetermined time after the motor 2 is started.
a, 58b and 58c are the starting rotor position signal generating circuit 5
2 side, after a predetermined time has elapsed, contacts 58a, 58b,
58c is connected to the side of the comparators 6a, 6b, 6c. Therefore, the switching signal generating circuit 54 is based on the starting rotor position signal from the starting rotor position signal generating circuit 52 for a predetermined time after starting, and after the predetermined time has elapsed, the comparator 6
Rotor position signals Va, Vb, Vc from a, 6b, 6c
Generates a switching signal based on These switching signals are transmitted to the semiconductor switching element with each control electrode of the semiconductor commutation circuit 1, for example, the transistor 1
0u, 10v, 10w, 12u, 12v, 12w. Each transistor 10u, 10v, 10w, 12
Free wheel diodes 20u, 20v, 20w, 22u, 22v, are connected in parallel to u, 12v, 12w, respectively.
22w is connected. These six transistors are three-phase bridge connected. Transistors 10u, 1
2u is for generating an excitation signal to the armature winding 3u, transistors 10v and 12v are for generating an excitation signal to the armature winding 3v, and transistors 10w and 12w are for generating an excitation signal to the armature winding 3w. The configuration for generating the switching signal to the semiconductor commutation circuit 1 in the control circuit 5 may be a known one, and therefore its detailed description will be omitted. Here, the starting rotor position signal generation circuit 52
Outputs a starting rotor position signal (waveforms similar to (g), (h), and (i) in FIG. 2) in which the duty ratio is the same and the frequency becomes higher as time elapses after the start. The duty ratio of the starting rotor position signal is the same as that of the rotor position signals Va, Vb, Vc, and its frequency is preferably substantially the same as the frequency of the rotor position signal at the synchronous speed when a predetermined time has elapsed. .

Next, the operation of this embodiment will be described with reference to FIG. At startup, the timer 50 of the control circuit 5
Connects the contacts 58a, 58b, 58c to the starting rotor position signal generating circuit 52 side for a predetermined time in response to a starting switch (not shown), and causes the starting rotor position signal generating circuit 52 to start the starting rotor. Generate a position signal. Therefore, the starting rotor position signal is transmitted to the contacts 58a, 58b, 5
8c is applied to the switching signal generation circuit 54, whereby the switching signal generation circuit 54 applies a switching signal having a duty ratio and frequency corresponding to the starting rotor position signal to the semiconductor commutation circuit 1 to start the brushless motor 2. To do. Here, the predetermined time is preferably a time required for the motor 2 to reach the synchronous speed, and the duty ratio is a duty ratio required for the motor 2 to rotate at the synchronous speed. When a predetermined time has elapsed after the motor 2 is started, the contacts 58a, 58 are controlled by the timer 50.
b and 58c are connected to the comparators 6a, 6b and 6c side, the output of the starting rotor position signal generating circuit 52 is stopped, and instead the rotor position signals Va and Vb from the comparators 6a, 6b and 6c are used. , Vc are applied to the switching signal generating circuit 54 via the contacts 58a, 58b, 58c. Therefore, the switching signal generation circuit 54 gives a switching signal to the semiconductor commutation circuit 1 based on the rotor position signals Va, Vb, Vc. Therefore, when a predetermined time elapses after the motor 2 is started, the switching signal to the commutation circuit 1 corresponds to the rotor position signals Va, Vb, Vc.

The switching signal generated by the switching signal generation circuit 54 will be described below. Motor 2
Is started, the armature winding 3u,
The waveforms of the phase voltages U, V, and W appearing at 3v and 3w are as shown in (a), (b), and (c) of FIG. Here, the characteristics of these phase voltage waveforms will be described by taking the phase voltage U as an example. First, the pulsed voltage appearing in the periods t1 to t2 is a voltage generated by turning off the transistor 12u corresponding to the U phase, and the gradually increasing voltage in the periods t2 to t3 is the armature winding 3u of the U phase. Is a counter electromotive force induced by approaching the magnetic pole of the rotor 4,
t6 is a voltage applied from the semiconductor commutation circuit 1 when the U-phase transistor 10u is turned on. When the transistor 10u is turned off at time t6, a negative pulse voltage appears at times t6 to t7.
The gradually decreasing voltage appearing in the period t7 to t8 is the counter electromotive force induced by the U-phase armature winding 3u moving away from the magnetic pole of the rotor 4. Here, the peak value of the pulse voltage in the periods t1 to t2 and the peak value of the counter electromotive force near the time t3 are both the transistor 10u in the periods t3 to t6.
The value slightly exceeds the applied voltage value Vum due to turning on. Further, both the negative peak value of the pulse voltage in the period t6 to t7 and the negative peak value of the counter electromotive force near the time t8 are
It is a value slightly lower than the voltage value 0V due to the turning off of the transistor 10u in the period t6 to t10. The voltage waveforms of the other phases have similar waveforms.

The phase voltages U, V, W appearing in the armature windings are supplied to the corresponding comparators 6a, 6b, 6c via the corresponding filters 9u, 9v, 9w. The phase voltages that have passed through the filters 9u, 9v, 9w, that is, the output voltages Vu, Vv, Vw of the filters 9u, 9v, 9w are shown in FIG.
(D), (e), (f). That is, for example, regarding the phase voltage of the U phase, the peak value of the pulse voltage in the periods t1 to t2 is less than the voltage Vum, and the peak value of the pulse voltage in the periods t6 to t7 is a value exceeding the voltage value 0V, but at time t3. The positive peak value of the back electromotive force in the vicinity is the voltage V
The value exceeds um, and the negative peak value of the back electromotive force near time t8 is less than the voltage value 0V. The time constant of each filter is set so that the positive and negative peak values of the pulse voltage are greatly reduced and the positive and negative peak values of the counter electromotive force unit are slightly reduced. Therefore, the positive and negative peak values of the output voltages Vu, Vv, Vw of the filters 9u, 9v, 9w correspond to the predetermined angular positions of the rotor.

Comparators 6a, 6b, 6c corresponding to the output voltages Vu, Vv, Vw of these filters 9u, 9v, 9w.
Is given to each of the comparators 6a, 6b, 6c, the difference (Vu−Vw), (Vv) between the corresponding output voltages Vu, Vv, Vw.
-Vu), (Vw-Vv) is calculated and output voltages Va, Vb,
Output as Vc ((g), (h), (i) in FIG. 2). That is, for example, in the comparator 6a, the output voltage Va shown in (g) of FIG. 2 is obtained by obtaining the difference between the output voltages Vu and Vw of the filters 9u and 9w. This is because, as described above, the output voltage Vu ((d) of FIG. 2) of the filter 9u has a positive peak near times t3 and t11 and a negative peak around time t8, for example.
Further, the output voltage Vw of the filter 9w (dotted line in (d) of FIG. 2) has a positive peak near time t9, and the time t5.
Since it has a negative peak near t12 and the like, the voltage obtained as the difference between the output voltages Vu and Vw becomes high level from time t3 to t8 and the like, and becomes low level from time t8 to t11 and the like. The output voltages Vb and Vc of the other comparators 6b and 6c also have the waveforms shown in (h) and (i) of FIG. The comparators 6a, 6b, 6c thus obtained
The output voltages Va, Vb, Vc of each correspond to a predetermined angular position of the rotor and become a rotor position signal of the motor 2. The output voltage of these comparators 6a, 6b, 6c is controlled by the control circuit 5
Is applied to the switching signal generating circuit 54 via the contacts 58a, 58b, 58c at, and as described above, the generating circuit 54 generates a switching signal based on these rotor position signals. Therefore, the transistors 10u, 12u, 10v, 12v, 10w of the commutation circuit 1
The output voltage of 12w is as shown in (j) to (o) of FIG.

Therefore, in this embodiment, the commutation circuit is operated by the switching signal from the switching signal generating circuit 54 based on the starting rotor position signal from the starting rotor position signal generating circuit 52 for a predetermined time after starting. 1 is controlled to drive the motor 2, and when a predetermined time has elapsed after the start-up, the commutation circuit 1 is controlled by the switching signal from the switching signal generation circuit 54 based on the rotor position signals Va, Vb, Vc, and the motor 2 is driven. To be done. Therefore, after a lapse of a predetermined time after starting, the motor 2 is controlled in accordance with the rotor position signal generated in synchronization with the counter electromotive force (rotational electromotive force), so that the motor 2 is stably maintained at the predetermined synchronization speed without being out of synchronization. It will be in steady operation.

A case in which the speed of the motor 2 changes due to load fluctuations of the motor 2 in such a state, for example, the speed becomes slower than the synchronous speed will be described with reference to FIG. In FIG. 3, the solid line shows the state at the synchronous speed, and the dotted line shows the state slower than the synchronous speed. For example, in the state where the motor is in steady operation at the synchronous speed, when the motor speed decreases, each phase voltage U, V, W, for example, the phase voltage U changes as shown in FIG. Filter 9
The output voltages Vu, Vv, Vw of u, 9v, 9w, for example, Vu also change as shown in FIG. Therefore, each rotor position signal Va, from each comparator 6a, 6b, 6c,
As shown in FIG. 3D, the rising phase of Vb and Vc, for example, Va is delayed, and the duty thereof is also increased. Therefore, the rotation speed of the motor 2 increases and returns to the synchronous speed promptly. Similarly, when the speed is higher than the synchronous speed, the synchronous speed is promptly restored.

In the above embodiment, the timer 50 is used, and the starter rotor position signal from the starter rotor position signal generating circuit 52 is used for a predetermined time after start-up, and the comparators 6a, 6b are operated when a predetermined time has passed after start-up. , 6c is applied to the switching signal generating circuit 54, but a speed detecting means for the motor 2 is provided in place of the timer to start the motor until the speed of the motor reaches the synchronous speed. The starting rotor position signal from the rotor position signal generation circuit 52 is
When the synchronous speed is reached, the rotor position signals from the comparators 6a, 6b and 6c may be given to the switching signal generating circuit 54.

[0018]

As described above, according to the present invention, the phase voltage of each pair of armature windings of a sensorless brushless motor is compared by a comparator, preferably through a filter. Since the rotor position signal of the motor is obtained, the rotor position signal can be obtained more accurately, and the circuit configuration required to obtain the rotor position signal only needs the comparator (and filter). Therefore, the circuit configuration can be simplified and an inexpensive rotor position signal generating circuit can be provided.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a rotor position signal generation circuit and a drive circuit of a sensorless brushless motor according to an embodiment of the present invention.

FIG. 2 is a timing chart showing signal waveforms in various parts of the circuit of the embodiment of FIG.

FIG. 3 is a timing chart showing signal waveforms for explaining the operation when the rotation speed of the motor changes in the embodiment of FIG.

[Explanation of symbols]

1 Commutation Circuit 2 Sensorless Brushless Motor 3u, 3v, 3w Armature Winding 4 Rotor 5 Control Circuit 6a, 6b, 6c Comparator 9u, 9v, 9w Low Pass Filter 10u, 10v, 10w, 12u, 12v, 12w Transistor 20u , 20v, 20w, 22u, 22v, 22w Freewheel diode

Claims (6)

[Claims] 1. A drive circuit of a sensorless brushless motor having a semiconductor commutation circuit in which a plurality of semiconductor switching elements are connected to an armature winding in a multi-phase bridge connection, the drive circuit being provided corresponding to the armature winding of the motor. A comparator (6a, 6a) for comparing the phase voltage of each pair of the armature windings to obtain the rotor position signal of the sensorless brushless motor.
b, 6c) and a switching signal generation circuit (5) for generating a switching signal to the semiconductor commutation circuit (1) based on the rotor position signals (Va, Vb, Vc) from the comparator. Drive circuit for a sensorless brushless motor characterized by: 2. In a drive circuit of a sensorless brushless motor having a semiconductor commutation circuit in which a plurality of semiconductor switching elements are connected to an armature winding in a multi-phase bridge connection, a filter (9u) connected to each of the armature windings. , 9v,
9w) and a comparator (6a, 6b, 6) provided corresponding to each of the filters and comparing the phase voltage of each pair of the armature windings to obtain a rotor position signal of the sensorless brushless motor.
and a switching signal generating circuit for generating a switching signal to the semiconductor commutation circuit based on a rotor position signal from the comparator, and a drive circuit for a sensorless brushless motor. 3. The sensorless brushless motor drive circuit according to claim 1, wherein the filter is a low-pass filter. 4. A rotor position signal generation circuit for a multi-phase sensorless brushless motor, wherein a comparator (6a, 6a, 6a, 6a, 6b) for comparing the phase voltage of each pair of armature windings corresponding to the armature windings of the motor is provided. 6b, 6c), and a rotor position signal generation circuit for a multi-phase sensorless brushless motor, wherein the rotor position signal for the sensorless brushless motor is obtained from the output of the comparator. 5. A rotor position signal generating circuit for a multi-phase sensorless brushless motor, wherein a filter (9u, 9v,
9w) and a comparator (6a, 6b, 6) provided corresponding to each of the filters and comparing the phase voltage of each pair of the armature windings to obtain a rotor position signal of the sensorless brushless motor.
c) and a rotor position signal generating circuit of a multi-phase sensorless brushless motor. 6. The drive circuit for a sensorless brushless motor according to claim 5, wherein the filter is a low-pass filter.