JP2003116293A - Parallel drive circuit of dc brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure a stabilized parallel operation at all times even when a load is not uniform. SOLUTION: A parallel drive circuit comprising a circuit 30 generating a switching signal using the rotor position detection signal of each motor in order to drive a plurality of DC brushless motors MA and MB connected in parallel is further provided with a signal select circuit 40 for delivering a control signal to the switching signal generating circuit 30 such that the rotor position detection signal used for generating a switching signal is switched between respective motors within a period where the rotor position detection signal of each motor does not vary and a switching signal is generated using a switched rotor position detection signal, and a speed control circuit 50 for detecting the shift of each rotor position detection signal and lowering the speed of each motor MA, MB when the shift exceeds a threshold.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a parallel drive circuit for driving a plurality of DC brushless motors that are connected in parallel to each other to operate a plurality of fans, pumps, etc. at the same speed.

[0002]

2. Description of the Related Art The present applicant previously applied for a parallel driving circuit of this type as Japanese Patent Application No. 2001-222412. That is, the parallel drive circuit according to the prior application is a parallel drive circuit that drives a plurality of DC brushless motors connected in parallel with each other at the same speed by a drive circuit having a plurality of semiconductor switching elements. In the parallel drive circuit of the DC brushless motor, wherein the means uses the rotor position detection signal of each motor to create the switching signal of the switching element, the switching signal is generated within a period in which the rotor position detection signal of each motor does not change. A signal selection unit that outputs a control signal to the switching signal generation unit so that the rotor position detection signal to be used is switched between the motors and a switching signal is created using the rotor position detection signal of the motor after the switching. Be prepared.

FIG. 8 shows the overall structure of the above-mentioned conventional description, and is a case where two DC brushless motors MA and MB are driven by one drive circuit. In FIG. 8, DC brassless motors MA and MB having the same configuration are connected in parallel to the output terminals U, V, and W of the three-phase bridge circuit, and Hall elements HU and H are provided in the respective DC brassless motors MA and MB.
V and HW are connected to the rotor position detection circuits 21 and 22.

The rotor position detection signals of the motors MA and MB output from the detection circuits 21 and 22 are input to the signal selection circuit 40, and the position detection signal of which motor MA or MB is used is switched. It is selectable. Then, from the signal selection circuit 40, the switching elements T1 to T are switched according to the position detection signal of the selected motor.
A control signal for the switching signal generation circuit 30 is output to turn on and off 6. In addition, 50 is a speed control circuit of each motor MA, MB.

As shown in FIG. 9, the signal selection circuit 40 includes XOR (exclusive OR) gates IC1 and IC2 to which a position detection signal of the motor MA is input, and an XOR gate IC.
NAND gates IC3 to IC7 connected to the output side of 2
, NAND gates IC8 to IC10 to which the position detection signal of the motor MB is input, and a resistor R1 such as a pull-up resistor
~ R10, capacitor C1, and NAND gate IC5
~ IC10 includes output side diodes D1 to D7 and output side transistors TR1 to TR3.
The signal selection circuit 40 is a motor M as shown in FIG.
When the position detection signal of each phase of A and MB is input, the switching signal generation circuit 30 outputs a control signal for driving the switching element of one phase or two phases of the motors MA and MB to the transistors TR1 to TR3. It works to output from.

The operation of the prior art shown in FIG. 8 will be described below with reference to FIGS. 9 and 10. Now, assuming that the motors MA and MB are synchronously operating at the same speed, their position detection signals are synchronously output as shown in FIG. In addition, in FIG. 10, the signal regarding the motor MA is A,
A signal relating to the motor MB is indicated by B.

In order to operate both motors MA and MB in synchronization with the position detection signal, the rotor rotation angle (spatial angle) in FIG. 10 is 0 °, 60 °, 120 °, 180 °, 24.
It is necessary to change the switching signal output from the switching signal generation circuit 30 in accordance with the change of the position detection signal at the timing of 0 ° and 300 °.

On the other hand, the rotation angle in FIG.
Between 60 ° and 120 °, between 120 ° and 180 °, between 180 ° and 240 °, between 240 ° and 300 °, and between 300 ° and 0 °, each motor MA, MB. In both cases, there is no change in the position detection signal, and a constant state is maintained.
Therefore, as described above, there is no adverse effect even if the position detection signal of the motor MA and the position detection signal of the motor MB are switched while the position detection signal remains unchanged and constant.

For example, a switching signal for driving the motor MA using the position detection signal of the motor MA (since the motors MA and MB are connected in parallel, the motor MB
When it is outputting a switching signal for driving the motor MB, the switching signal for switching the position detection signal of the other motor MB to drive the motor MB (also the switching signal for driving the motor MA). (Possible) is output, if the switching is performed during a period when the position detection signal does not change, there is no concern that the voltage applied to the motor suddenly changes at the moment of switching. Further, if the switching is performed in a cycle shorter than the cycle of the position detection signal as in this example, there is little possibility that the operation becomes unstable.

Therefore, in this conventional technique, the angle is 0 ° to 6 °.
0 °, 60 ° to 120 °, 120 ° to 180 °
, 180 ° to 240 °, 240 ° to 300 °, 300 ° to 0 ° (360 °), 30 °, 9
At the time of 0 °, 150 °, 210 °, 270 °, and 330 °, the signal selection circuit 40 alternately selects the position detection signals of the motors MA and MB between the motors to select the selected position detection signal. Based on the motor MA,
A switching signal for driving the MB is output.

That is, as shown in FIG. 10, for example, 330
The position detection signal of the motor MA is selected between 0 ° and 30 °, and the switching signal generation circuit 3 is selected based on this signal.
0 outputs a switching signal so that the U-phase coil CU and the W-phase coil CW are energized (the periods are different). Further, the position detection signal of the motor MB is selected between 30 ° and 90 °, and the switching signal generation circuit 30 energizes the U-phase coil CU and the W-phase coil CW based on this signal (the period is different from each other). ) To create a switching signal. Thereafter, similarly, the position detection signal of the motor MA is selected between 90 ° and 150 °, and the switching signal generation circuit 30 is based on this signal and the switching signal generation circuit 30 outputs the U-phase coils CU and V.
A switching signal is created so as to energize the phase coil CV, and a position detection signal of the motor MB is selected between 150 ° and 210 °, and the switching signal generation circuit 30 determines the U phase coil CU, V phase based on this signal. A switching signal is created so that the coil CV is energized.

In FIG. 10, the angle is 30 for convenience of explanation.
°, 90 °, 150 °, 210 °, 270 °, 330 °
The position detection signals of the motors MA and MB are switched by, but between 0 ° and 60 °, between 60 ° and 120 °, 120
Between 180 ° and 180 °, 240 ° between 180 ° and 240 °
The same effect can be obtained by switching at any angle between 300 ° and 300 ° and between 0 ° (360 °) and the position detection signals of the motors MA and MB do not change.

When the operation of the signal selection circuit 40 shown in FIG. 9 is confirmed, for example, rotor position detection signals (U phase, V phase, etc.) of the motors MA and MB between 30 ° and 60 ° in FIG.
If the W phase) is expressed by logic (1, 0, 1) and these are inputted as position detection signals of the motors MA and MB, the output side transistor T is converted by the logic circuit of FIG.
The logic of the output signals of R1, TR2 and TR3 (U-phase, V-phase, W-phase) is (1, 0, 1), and the position detection signals of the motors MA and MB between the next 60 ° and 90 ° ( U phase, V phase, W
If all the phases are logic (1, 0, 0), output side transistors TR1, TR2, TR3 (U phase, V phase, W phase)
The output signal has a logic of (1, 0, 0),
It can be seen that it matches the change of the output (control signal) of the signal selection circuit in the period of 0 ° to 90 °.

By the above operation, the two motors M
It is possible to stably drive A and MB in parallel with a single drive circuit in synchronization with the rotor position detection signal. The switching elements are PWM (pulse width modulation) so that the voltages applied to the motors MA and MB are equivalently sine waves.
A sine wave PWM control method for controlling is well known. Applying this method to the switching signal generation circuit 30, PW
By driving the switching element with M pulses, the motor can be operated more stably.

[0015]

In the above-mentioned prior art, there is no problem if the two motors MA and MB have exactly the same load states. For example, a fan of a cooling tower installed outdoors by these motors, etc. When each is driven, the natural wind may not evenly reach each fan.
For this reason, the magnitudes of the loads on the motors MA and MB become uneven, and there is a possibility that the operation becomes unstable, especially when the speed is increased.

Therefore, the present invention is intended to provide a parallel drive circuit for a DC brushless motor, which enables stable parallel operation at all times even when the loads are uneven and which can be provided at low cost.

[0017]

In order to solve the above-mentioned problems, the invention described in claim 1 has a plurality of DC brushless motors connected in parallel with each other at the same speed by a drive circuit having a plurality of semiconductor switching elements. Is a parallel drive circuit of a DC brushless motor for generating the switching signal of the switching element by using the rotor position detection signal of each motor, and the rotor position detection signal of each motor is The switching signal generating means is configured to switch the rotor position detection signal used to create the switching signal between the motors within a period that does not change, and to create the switching signal using the rotor position detection signal of the switched motor. In a parallel drive circuit having a signal selection means for outputting a control signal to Detecting a deviation of each rotor position detection signal, in which this shift with a speed control means for controlling to reduce the speed of the motors when the threshold is exceeded.

According to the second aspect of the present invention, the current flowing through the stator of each motor is detected, and when the difference in the magnitude of the current exceeds a threshold value, the speed of each motor is controlled to be reduced. It is provided with speed control means.

According to a third aspect of the present invention, there is provided speed control means for detecting a current flowing through the stator of each motor and controlling so as to reduce the speed of each motor when the magnitude of the current exceeds a threshold value. Be prepared.

According to a fourth aspect of the present invention, the pulsating component of the current flowing through the stator of the motor is detected, and when the magnitude of the pulsating component exceeds a threshold value, the speed is controlled so as to reduce the speed of each motor. It is provided with a control means.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a first embodiment of the present invention corresponding to the invention of claim 1, and the same components as those in FIG. 8 are designated by the same reference numerals.

In this embodiment, the rotor position detection signals of the motors MA and MB are input to the phase difference detection circuit 60, and the phase difference detection signal corresponding to the phase difference of the position detection signals is input to the speed control circuit 50. . The signal selection circuit 40
Performs the same operation as described with reference to FIG. 8, and its internal configuration is also the same as in FIG.

The operation of this embodiment will be described below with reference to FIGS. Now, assuming that the loads of the motors MA and MB are fans and the motors MA and MB are synchronously operating at the same speed, the rotor position detection signals of the motors MA and MB are as shown in FIG. In FIG. 2, a signal regarding the motor MA is indicated by A and a signal regarding the motor MB is indicated by B. In order to operate both motors MA and MB in synchronization with the position detection signal, the rotor rotation angles are 0 °, 60 °, 120 °, 180 °, 240 °, 30.
It is necessary to change the switching signal output from the switching signal generation circuit 30 in accordance with the change of the position detection signal at the timing of 0 °.

On the other hand, the rotation angle in FIG. 2 is 0 ° to 60 °.
Between 60 ° and 120 °, between 120 ° and 180 °, between 180 ° and 240 °, between 240 ° and 300 °, and between 300 ° and 0 °, both motors MA, MB The position detection signal does not change and maintains a constant state (for example, between 0 ° and 60 °, the U-phase and W-phase signals continue to be detected as the position detection signals of the motors MA and MB, Between 60 ° and 120 °, the state in which only the U-phase signal is detected as the position detection signal of the motors MA and MB continues).

Therefore, there is no adverse effect even if the position detection signal of the motor MA and the position detection signal of the motor MB are switched while the position detection signal remains unchanged and does not change as described above. For example, a switching signal for driving the motor MA using the position detection signal of the motor MA (which may be a switching signal for driving the motor MB because the motors MA and MB are connected in parallel) is output. While switching to the position detection signal of the other motor MB and outputting a switching signal for driving the motor MB (which may also be a switching signal for driving the motor MA), the switching is performed. If the operation is performed during the period when the position detection signal does not change, there is no concern that the voltage applied to the motor suddenly changes at the moment of switching. Further, if the switching is performed in a cycle shorter than the cycle of the position detection signal as in this example, there is little possibility that the operation becomes unstable.

Therefore, in this embodiment, the angle is from 0 ° to
Between 60 °, 60 ° to 120 °, 120 ° to 180
Between 180 ° and 240 °, between 240 ° and 300 °
Between 30 °, which is between 300 ° and 0 ° (360 °),
At 90 °, 150 °, 210 °, 270 °, and 330 °, the signal selection circuit 40 alternately switches the position detection signals of the motors MA and MB between the motors to select the selected position detection signals. Based on the motor MA,
A switching signal for driving MB is output.

That is, as shown in FIG. 2, for example, 330 °
The position detection signal of the motor MA is selected between ˜30 °, and the switching signal generation circuit 30 is selected based on this signal.
Outputs a switching signal so that the U-phase coil CU and the W-phase coil CW are energized (the periods are different from each other).
Further, the position detection signal of the motor MB is selected between 30 ° and 90 °, and the switching signal generation circuit 30 energizes the U-phase coil CU and the W-phase coil CW based on this signal (the period is different from each other). ) To create a switching signal.

Similarly, thereafter, the position detection signal of the motor MA is selected between 90 ° and 150 °, and the switching signal generating circuit 30 energizes the U-phase coil CU and the V-phase coil CV based on this signal. Create a switching signal,
A position detection signal of the motor MB is selected between 150 ° and 210 °, and the switching signal generation circuit 30 creates a switching signal based on this signal so as to energize the U-phase coil CU and the V-phase coil CV.

In FIG. 2, for convenience of explanation, the angle is 30 °,
The position detection signals of the motors MA and MB are switched at 90 °, 150 °, 210 °, 270 °, and 330 °, but the switching angle is not limited to these values, and as described above, 0 ° to 60 °. Between 60 ° and 120 °, 1 °
Between 20 ° and 180 °, between 180 ° and 240 °, 24
The same effect can be obtained by switching at any angle between 0 ° and 300 °, between 300 ° and 0 ° (360 °), and where the position detection signals of the motors MA and MB do not change. As described above, when the two motors MA and MB are synchronously operated at the same speed, the phase difference detection signal is not output as shown in FIG.

Next, when the loads of the two motors MA and MB are different, the synchronization of the motors MA and MB is deviated, and the position detection signals of the two deviate. FIG. 3 is a timing chart when the synchronization shift occurs. Since the load of the motor MB is larger than that of the motor MA, the position detection signal of the motor MB is output with a delay of 15 °. The delay of this position detection signal becomes large according to the difference in the magnitude of the load.

The operation of the signal selection circuit 40 is the same as when the two motors MA and MB are synchronously operated, but in the state of FIG. 3, the position detection signals of both motors MA and MB change. 15 years without maintaining a certain state
Between ° ~ 60 °, between 750 ° ~ 120 °, 135 ° ~
Between 180 °, 195 ° to 240 °, 255 ° to 3
Since it is between 315 ° and 0 ° (360 °) during 00 °, the rotor position detection signal is switched within each of these periods. As a result, the rotor position detection signal is
It switches at the same timing as.

When the motors MA and MB are out of synchronization as shown in FIG. 3, a phase difference detection signal is output and this signal is input to the speed control circuit 50. In FIG. 3, the phase difference detection signals are shown as “F” and “L”, where “F” means “lead” and “L” means “lag”. In this example, the position detection signal of the motor MB is delayed (the position detection signal of the motor MA is advanced), but for convenience, the rotor position detection signal selected by the signal selection circuit 40 is focused on. Since "advance" and "delay" are determined, for example, the phase difference between 0 ° and 15 ° (the position detection signal of the motor MA is selected) is "F", 60 ° to 7
The phase difference between 5 ° (the position detection signal of the motor MB is selected) is represented as “L”, ....

The speed control circuit 50 receives the phase difference detection signal and controls the speeds of the motors MA and MB. When the phase difference detection signal continues for a certain period of time or when the phase difference becomes a certain angle or more. In this case, it operates so as to reduce the speed of the motors MA and MB. Here, FIG. 4 shows the speed-load torque characteristics of the motors MA and MB. In this example, the load on the motor MB is larger than the load on the motor MA as described above, and the two motors MA, M
It can be seen that as the speed of B decreases, the difference in load torque decreases.

Therefore, when a phase difference occurs in the position detection signals due to the difference in the loads on the motors MA and MB, the speeds of the motors MA and MB are controlled to decrease.
The control for reducing the load difference is performed, and the parallel operation is performed in the direction of eliminating the synchronization deviation. This allows
Coupled with the operation of the signal selection circuit 40, the two motors M
A and MB can be stably operated in parallel.

Next, FIG. 5 is a circuit diagram showing a second embodiment of the present invention corresponding to the invention of claim 2. In this embodiment, the U-phase coil CU of each stator of the motors MA and MB
The current flowing through is detected by the current detectors CTA and CTB, and the detected current values are input to the current difference detection circuit 70. Then, this current difference detection signal is input to the speed control circuit 50. The speed control circuit 50 controls the motors MA, MB when the difference in the magnitude of the currents exceeds the threshold value.
It works to slow down. The operation of the signal selection circuit 40 is the same as that of the first embodiment.

When the two motors MA and MB have different loads, the motors MA and MB are out of synchronization with each other and the magnitude of the current flowing through the stators of the motors MA and MB varies. A difference occurs and this difference increases with the difference in load magnitude. That is, the difference between the currents flowing through the motors MA and MB can be regarded as the difference in the load magnitudes.
As described above, the difference in the magnitude of the load changes according to the speed. Therefore, if the speed of the motors MA and MB is controlled to decrease according to the current difference detected by the current difference detection circuit 70, the difference between the loads will be reduced. The control is performed in the direction of decreasing.
Therefore, in combination with the operation of the signal selection circuit 40, 2
It is possible to stably operate the motors MA and MB in parallel.

FIG. 6 is a circuit diagram showing a third embodiment of the present invention corresponding to the third aspect of the invention. In this embodiment, the currents flowing through the U-phase coils CU of the motors MA and MB are detected by the current detectors CTA and CTB, and the detected current values are input to the current comparison circuits 80A and 80B, respectively. The current comparison circuits 80A and 80B compare the magnitudes of the currents of the motors MA and MB with threshold values, and output signals to the speed control circuit 50 when the threshold values are exceeded. The speed control circuit 50, to which this signal is input, performs control operation so as to reduce the speeds of the motors MA and MB. The operation of the signal selection circuit 40 is the same as that of the first embodiment.

Now, when the load of one of the two motors MA and MB becomes large, the current flowing through that motor becomes large, and its magnitude corresponds to the magnitude of the load. At the same time, the difference between the loads of the motors MA and MB also increases, and the phase detection signal shift (synchronization shift) also increases. Further, in machines such as fans and pumps, the load torque increases as the speed increases, and the two motors MA,
The difference in the magnitude of the load on the MB is also large.

Therefore, the current comparison circuit 80A or 80B
When it is detected that the current of one of the motors exceeds the threshold value, the speed control circuit 50 causes the motor M to
If control is performed so as to reduce the speeds of A and MB, the control is performed in the direction of reducing the load difference. Accordingly, in combination with the operation of the signal selection circuit 40, the two motors M
A and MB can be stably operated in parallel.

FIG. 7 is a circuit diagram showing a fourth embodiment of the present invention corresponding to the fourth aspect of the invention. In this embodiment, the current detector CT is connected to the U-phase output line of the three-phase bridge circuit, and the detected current value is the pulsation component detection circuit 9
It is input to 0. The pulsation component detection circuit 90 detects the pulsation component of the U-phase current by a filter, compares the magnitude of the pulsation component with a threshold value, and when the pulsation component exceeds the threshold value, signals it to the speed control circuit 50. Is output. In the speed control circuit 50 to which this signal is input, the motors MA, MB
The control operation is performed so as to reduce the speed of. The operation of the signal selection circuit 40 is the same as that of the first embodiment.

Now, when the load of one of the two motors MA and MB becomes large, the current flowing through the motor becomes large, and its magnitude corresponds to the magnitude of the load. At the same time, the difference between the loads of the motors MA and MB also increases, and the phase detection signal shift (synchronization shift) also increases and the operation becomes unstable. Also, two motors MA,
When the magnitude of the current of MB changes, the pulsating component of the current supplied from the three-phase bridge circuit increases, and the pulsating component increases as the difference in the magnitude of the load increases. Furthermore,
In machines such as fans and pumps, the load torque increases as the speed increases, and the difference in load between the two motors MA and MB also increases.

Therefore, when the magnitude of the pulsating component detected by the pulsating component detecting circuit 90 exceeds the threshold value, if the speed control circuit 50 controls so as to reduce the speeds of the motors MA and MB, the difference between the loads will be reduced. The control is performed in the decreasing direction. Accordingly, in combination with the operation of the signal selection circuit 40, the two motors MA and MB can be stably operated in parallel. In the embodiment of FIG. 7, the output current of the three-phase bridge circuit, that is, the two motors MA and M.
Although the pulsating component is detected by detecting the combined current of B, the pulsation of each motor MA, MB is provided by providing the current detectors CTA, CTB to each motor MA, MB as in FIGS. You may make it compare the magnitude | size of a component with each threshold value.

Needless to say, the present invention is most effective when the motors having the same characteristics are used as the two motors MA and MB and the characteristics of the load such as the fan are also the same. Furthermore, in each of the above-described embodiments, the case where two DC brushless motors are operated in parallel has been described, but the present invention is also applicable to the case where three or more motors are operated in parallel.

[0044]

As described above, according to the present invention, it is possible to stably drive a plurality of DC brushless motors by one drive circuit, as compared with the case where a drive circuit is provided for each motor. It can be provided at low cost. In particular, the present invention relates to indoor or outdoor fans for air conditioners that are operated in parallel, fans for fan coil units, fans for fan filter units, fans for buildings and homes, ventilation fans, air conditioning fans, cooling fans for vending machines, and various types. It is suitable to apply to a DC brushless motor that uses a pump or the like as a load.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a timing chart showing the operation of FIG.

FIG. 3 is a timing chart showing the operation of FIG.

FIG. 4 is a diagram showing speed-load torque characteristics of each motor in the embodiment of FIG.

FIG. 5 is a circuit diagram showing a second embodiment of the present invention.

FIG. 6 is a circuit diagram showing a third embodiment of the present invention.

FIG. 7 is a circuit diagram showing a fourth embodiment of the present invention.

FIG. 8 is a circuit diagram showing a conventional technique.

9 is a circuit diagram showing a configuration of a signal selection circuit in FIG.

FIG. 10 is a timing chart showing the operation of the conventional technique.

[Explanation of symbols] E DC power supply T1-T6 switching elements U, V, W output terminals MA, MB DC brushless motor CU, CV, CW coil HU, HV, HW Hall element CT, CTA, CTB current detector 11 Stator 12 rotor 21,22 Rotor position detection circuit 30 Switching signal generation circuit 40 signal selection circuit 50 speed control circuit 60 Phase difference detection circuit 70 Current difference detection circuit 80A, 80B current comparison circuit 90 Pulsation component detection circuit

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5H560 AA01 AA02 BB04 BB12 CC03                       DA02 DC12 EB01 SS01 UA02                       XA02 XA04

Claims (4)

[Claims] 1. A switching signal generating means outputs a rotor position detection signal of each motor in order to drive a plurality of DC brushless motors connected in parallel with each other at the same speed by a drive circuit having a plurality of semiconductor switching elements. A parallel drive circuit of a DC brushless motor for generating a switching signal of the switching element by using the parallel drive circuit, wherein the rotor position detection signal of each motor does not change,
The rotor position detection signal used to create the switching signal is switched between the motors, and a control signal is output to the switching signal generating means so as to create the switching signal using the rotor position detection signal of the switched motor. In the parallel drive circuit including the signal selecting means, the deviation of each rotor position detection signal is detected, and when the deviation exceeds a threshold value, the speed control means for controlling to reduce the speed of each motor is provided. A parallel drive circuit of a DC brushless motor characterized by the above. 2. A switching signal generating means outputs a rotor position detection signal of each motor in order to drive a plurality of DC brushless motors connected in parallel to each other at the same speed by a drive circuit having a plurality of semiconductor switching elements. A parallel drive circuit of a DC brushless motor for generating a switching signal of the switching element by using the parallel drive circuit, wherein the rotor position detection signal of each motor does not change,
The rotor position detection signal used to create the switching signal is switched between the motors, and a control signal is output to the switching signal generating means so as to create the switching signal using the rotor position detection signal of the switched motor. In the parallel drive circuit equipped with the signal selecting means, the current flowing in the stator of each motor is detected, and the speed of each motor is controlled to decrease when the difference in the magnitude of the current exceeds the threshold value. A parallel drive circuit for a DC brushless motor, comprising a speed control means. 3. A plurality of DC brushless motors connected in parallel with each other are driven at a same speed by a drive circuit having a plurality of semiconductor switching elements, and a switching signal generating means outputs a rotor position detection signal for each motor. A parallel drive circuit of a DC brushless motor for generating a switching signal of the switching element by using the parallel drive circuit, wherein the rotor position detection signal of each motor does not change,
The rotor position detection signal used to create the switching signal is switched between the motors, and a control signal is output to the switching signal generating means so as to create the switching signal using the rotor position detection signal of the switched motor. In the parallel drive circuit equipped with the signal selecting means, the speed control means for detecting the current flowing through the stator of each motor and controlling so as to reduce the speed of each motor when the magnitude of the current exceeds the threshold value is provided. A parallel drive circuit for a DC brushless motor, which is characterized by being provided. 4. A switching signal generating means outputs a rotor position detection signal of each motor in order to drive a plurality of DC brushless motors connected in parallel with each other at the same speed by a drive circuit having a plurality of semiconductor switching elements. A parallel drive circuit of a DC brushless motor for generating a switching signal of the switching element by using the parallel drive circuit, wherein the rotor position detection signal of each motor does not change,
The rotor position detection signal used to create the switching signal is switched between the motors, and a control signal is output to the switching signal generating means so as to create the switching signal using the rotor position detection signal of the switched motor. The speed at which the pulsating component of the current flowing through the stator of the motor is detected in the parallel drive circuit equipped with the signal selecting means, and the speed of each motor is controlled to decrease when the magnitude of the pulsating component exceeds the threshold value. A parallel drive circuit for a DC brushless motor, comprising a control means.