JP2001190083A - Driving circuit of motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the noise and rotation irregularity of a motor in the driving circuit of a general purpose three-phase DC brushless motor. SOLUTION: In this driving circuit of a motor, timing in three-phase conduction phase switching (commutation) is detected by a timing detection circuit, and a PWM pulse is turned on forcedly for set time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit for a general-purpose three-phase DC brushless motor, and to a method for reducing noise and uneven rotation of the motor.

[0002]

2. Description of the Related Art FIG. 3 is a diagram showing the configuration of a drive circuit of a three-phase DC brushless motor having a general star connection. Reference numeral 1 denotes a multipolar magnetized magnet, and 2 denotes a magnetic pole position of the magnet 1. A three-phase amplifier group for amplifying the output of the two Hall elements, and a four-phase amplifier for amplifying the output of the two Hall elements. An energizing logic circuit for outputting a signal, 8 is a star-connected motor winding, 9 is an output line of the motor winding 8, 7 is an inverter circuit for energizing the motor winding 8 in bipolar (both directions), and 10 is an inverter. An upper arm transistor group including a freewheeling diode, which constitutes the circuit 7, 11
Denotes a lower arm transistor group including a freewheeling diode which constitutes the inverter circuit 7, 5 denotes a signal group to the upper arm transistor group 10 of the energizing logic circuit 4, 6 denotes a signal group to the lower arm transistor group 11 of the energizing logic circuit 4, 16 is a frequency generator directly connected to the motor rotation shaft, 14 is an F / V circuit that converts a signal of the frequency generator 16 into a voltage, 15 is a speed command voltage that regulates the number of revolutions, and 13 is a speed command voltage 15.
And a differential amplifier having an output of the F / V circuit 14 which is a voltage proportional to the rotation speed.
This is a PWM circuit for converting into M pulses.

FIG. 4 is a timing chart of signals when the driving circuit is operated. A, B, and C are outputs of the amplifier 3 for three phases (U, V, and W phases), and D is an upper arm. E is a U-phase output of the transistor group 5; E is a U-phase output of the lower arm transistor group 6 by a PWM pulse such as F; G is an energization signal for the U phase of the winding 8; The ON state and the concave side indicate the lower arm transistor ON state. H is a current waveform flowing in the U phase,
J is the midpoint voltage of the star-connected motor winding 8 in the U-phase upper arm transistor ON state. Paying attention to the current waveform in the U-phase upper arm transistor ON state, the rise of the current waveform in part a is delayed due to the influence of the motor winding inductance. In part b, the rise of the current due to the commutation of the other phase is slow, during which the U-phase current falls. The part c continues to flow even after the end of the energization signal until the current energy stored in the motor winding is released via the return diode. In the U-phase upper arm transistor ON section of the midpoint voltage J of the motor winding, the d portion is the V-phase lower arm transistor ON, the e portion is the W-phase lower arm transistor ON, and when the voltage is Vcc / 2, the lower portion is lower. Arm transistor is O
N. Further, the voltage drop in the f section is caused by the commutation of the W phase, and the voltage jump in the g section is V
The commutation of the phase causes the voltage drop in the h section due to the commutation of the U phase itself.

[0004]

In the conventional configuration as described above, the rise of the current is delayed after commutation due to the influence of the inductance of the motor winding, and the current drops near the conduction center of the other phase. This current drop is steep and causes motor noise. Further, since the rotational torque of the motor is the product of the interlinkage magnetic flux of the motor winding and the value of the energizing current, there is a problem that the rotational torque is reduced when the current drops, which causes uneven rotation.

[0005]

A motor drive circuit according to the present invention generates a pulse obtained by multiplying the output of a magnetic pole position sensor built in a three-phase DC brushless motor by six, and rises and falls of the six-multiplied pulse. Is synchronized with the commutation timing of the three phases of the motor by the time constant circuit, and the designated pulse width composite pulse is forcibly set for the set time.
A motor drive circuit characterized in that a WM pulse is set to an ON state.

[0006]

The timing of the three-phase commutation is detected by a simplified circuit, and the PWM pulse is forcibly turned on for a certain time immediately after the commutation, thereby delaying the rise of the current due to the winding inductance of the motor. To reduce. By giving an appropriate ON time, the rise and delay of the current flowing through the motor winding can be reduced, and at the same time, the drop near the central portion of the current can be improved. As a result, noise is reduced and uneven rotation is also improved.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a drive circuit of a three-phase DC brushless motor according to the present invention. In FIG. 3, a pulse generated by multiplying the output of a three-phase amplifier 3 by six is shown in FIG.
A timing detection circuit 17 that detects the rise and fall of the multiplied pulse and generates a pulse having a certain pulse width synchronized with the commutation timing of the three phases of the motor by a time constant circuit is added, and is input to the PWM circuit 12.

FIG. 2 is a timing chart for explaining the present invention, in which an output pulse K of a timing detection circuit 17 is added to FIG. In synchronism with the timing pulse K, the output F 'of the PWM circuit 12 has a longer low ("L") section. Since the PWM pulse is "L" and energized ON, the maximum voltage is applied to the motor winding for a certain time immediately after the commutation timing, and the delay of the rise time of the current is improved as shown by a '. . As a result, it is possible to eliminate the current drop in the portion b ′. J ′ is the midpoint voltage waveform according to the present invention.

In the above description, the ON duty of the PWM is set to 100% immediately after the commutation. However, it is also effective when the PWM duty is limited to a certain value, and the PWM control is applied to the lower arm transistor of the inverter circuit. However, when the PWM control is applied to the upper arm transistor or the upper and lower arms, the same effect as the present invention can be obtained.

[0010]

According to the motor drive circuit of the present invention, the following effects can be obtained. (1) Distortion of the current waveform is reduced, which has a remarkable effect on lowering the noise of the motor and improving rotation unevenness. (2) The three-phase star connection is effective for all PWM (upper arm, lower arm, upper / lower arm, alternate arm) drive systems using the inductance of the motor winding. (2) The configuration of the present driving circuit is simplified, and it is easy to make it into an IC, and it can be realized without increasing the cost compared to the conventional driving circuit. (3) From the above effects, the range of use as a wide-range drive motor for information processing equipment, audio equipment, office equipment, and medical equipment equipped with a small, three-phase star-connected DC brushless motor is expanded.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a motor three-phase DC brushless drive circuit according to the present invention.

FIG. 2 is a timing chart of a three-phase DC brushless motor drive circuit according to the present invention.

FIG. 3 is a configuration diagram of a conventional three-phase DC brushless motor drive circuit.

FIG. 4 is a timing chart of a conventional three-phase DC brushless motor drive circuit.

[Explanation of symbols]

 1: magnet 2: hall element group 3: amplifier group 4: energization logic circuit 5: signal group 6: signal group 7: inverter circuit 8: motor winding (three-phase star connection) 9: output line 10: upper arm transistor group 11: Lower arm transistor group 12: PWM circuit 13: Differential amplifier 14: F / V circuit 15: Speed command voltage 16: Frequency generator 17: Timing detection circuit A: U-phase amplifier output B: V-phase amplifier output C: W-phase amplifier output D: U-phase output of upper arm transistor E: U-phase output of lower arm transistor F: PWM pulse G: Motor winding U-phase conduction signal H: U-phase current waveform J: Motor winding middle point Voltage K: Output of timing detection circuit F ': PWM pulse of the present invention J': Midpoint voltage of motor winding of the present invention

Claims (2)

[Claims] 1. A PWM control circuit that uses a winding inductance of a motor and a motor winding of 120 degrees (electrical angle) in order to rotate a DC brushless motor having a winding of a three-phase star connection at a constant speed. In the motor drive circuit that energizes in both directions (bipolar), the timing of the three-phase energized phase switching (commutation) is detected by the timing detection circuit, and the ON duty of the PWM pulse is forcibly set for a set time immediately after the commutation. Motor drive circuit characterized by widening the range. 2. A pulse generated by multiplying the output of a magnetic pole position sensor built in a three-phase DC brushless motor by six, a rising edge and a falling edge of the six-multiplied pulse are detected, and a three-phase rotation of the motor is detected by a time constant circuit. 2. The timing detection circuit according to claim 1, wherein a synthesized pulse having a designated pulse width is generated in synchronization with the flow timing.