JP3252305B2 - Drive device for brushless DC 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 driving device for a brushless DC motor, and more particularly to a driving device for detecting a phase current of the DC motor to drive the DC motor.

[0002]

2. Description of the Related Art Conventionally, in the field of driving automatic doors and coolers, for example, a three-phase DC brushless motor (hereinafter abbreviated as a motor) has been used.

FIG. 4 is a block diagram of a drive circuit 1 for a brushless DC motor (hereinafter referred to as a motor) according to the prior art. The motor 2 has a three-phase stator having three coils 3, 4, 5 to which U-phase, V-phase and W-phase drive signals Iu, Iv, Iw are supplied. Motor 2
Is a rotor 6 made of a permanent magnet or the like having a pair of magnetic poles.
Is provided. Further, the motor 2 includes a magnetic pole detecting element 7 configured of a Hall element or the like for detecting the rotation speed of the rotor 6 and outputting magnetic pole signals Hu, Hv, Hw for each phase.

[0004] The drive circuit 1 includes coils U, U,
Circuit for supplying drive signals Iu, Iv, Iw of the three-phase, V-phase and W-phase, respectively.
, The six transistors Q1, Q2, Q3, Q
4, Q5 and Q6 are provided. Each transistor Q1-Q
6 and diodes D1, D2, D3, D
4, D5 and D6 are provided. Each diode D1 to D6
Are connected to the sources of the transistors Q1 to Q6, and the transistors Q1 to Q6 are connected to the DC power supply 8. Transistors Q1, Q4; Q2, Q5; Q3, Q
6 from each connection point, the U-phase, V-phase and W-phase drive signals I
u, Iv, and Iw are output, respectively. Transistor Q
The sources of 4 to Q6 are connected to the negative electrode of the DC power supply 8 via the current detection resistor 25.

The magnetic pole detecting element 7 is connected to a frequency / voltage conversion circuit (hereinafter, conversion circuit) 9 and an energization logic circuit 10. The output of the conversion circuit 9 is compared with the command data from the speed command input unit 11 for inputting the command data corresponding to the predetermined number of rotations of the motor 2 in the calculation unit 12, and sent to the PWM circuit 14 via the buffer 13. Is entered. In the PWM circuit 14, the signal from the buffer 13 is compared with the triangular wave from the triangular wave generation circuit 15 by the comparison circuit 16, and a PWM signal is output. The PWM circuit 1
4 are commonly input to AND circuits 17, 18, and 19.

The voltage between the terminals of the current detecting resistor 25 is
The signal is inverted and input to the comparison circuit 23, and is compared with a reference potential from a power supply 24 that generates a predetermined reference potential. The output of the comparison circuit 23 is input to the current limiting circuit 22.
The current limiting circuit 22 outputs a low-level current limiting signal when the voltage between the terminals of the current detecting resistor 25 exceeds the reference potential. When the voltage between the terminals of the current detection resistor 25 is lower than the reference potential, a high level current permission signal is output. The output of the current limiting circuit 22 is input to the AND circuits 17 to 19 in common.

The energization logic circuit 10 has six types of drive signals U, which are inputted to the gates of the transistors Q1 to Q6 to switch on / off the transistors Q1 to Q6.
EU, V, EV, W, and EW are output. The drive signal U,
V and W are input to the gate drive circuit 9, drive signals EU, EV and EW are input to the AND circuits 17 to 19, respectively, and outputs of the AND circuits 17 to 19 are input to the gate drive circuit 9. You. The gate drive circuit 9 outputs the drive signals U, EU, V, EV, W, EW
The signal level is converted into a signal level that can be input to the transistors Q1 to Q6, and input to the transistors Q1 to Q6, respectively.

FIG. 5 is a time chart for explaining the operation of the driving device 1 according to the prior art.

FIGS. 5A to 5C show magnetic pole signals from the magnetic pole detecting element 7 for each phase.

FIGS. 5 (4) to 5 (9) show drive signals U and E, respectively.
U, V, EV, W, and EW are shown.

FIGS. 5 (10) to 5 (12) show each coil 3,
4 shows coil currents Iu, Iv, Iw flowing through 4, 5 respectively.

FIG. 5 (13) shows the electric angle of the motor 2. In this conventional example, 120-degree energization is performed.

[0013]

In the above prior art, the coil current flowing through each of the coils 3 to 5 decreases at the rising timing and the falling timing of the drive signals U, EU, V, EV, W, EW. Or, when it increases, as shown in FIGS. 5 (10) to (12), a delay occurs in the coil currents Iu, Iv, Iw due to the self-inductance of each of the coils 3 to 5. As a result, the generated torque of the motor becomes discontinuous, and the torque ripple in the motor 2 increases. Due to this torque ripple, the vibration of the motor 2 increases. Therefore, there is a problem that the motor 2, a mounting portion around the motor 2, or a fan when the motor 2 is used as a fan motor generate resonance and increase noise.

An object of the present invention is to solve the above-mentioned technical problems and to provide a drive device for a brushless DC motor with increased quietness.

[0015]

According to the present invention, there is provided a brushless DC motor driving apparatus comprising: a plurality of switch elements for supplying driving power to coils of respective phases of a brushless DC motor having a plurality of phases of coils; A plurality of current detecting resistors respectively connected to at least a part of the switch element, and detecting a rotation speed of a rotor of the motor.
Magnetic pole detection element and switching operation of the switch element
In synchronization with the voltage between the terminals of the plurality of current detection resistors.
By holding each sample, the mode
Coil current for each phase of the motor
It changes every 60 electrical degrees depending on the detection signal from the pole detection element.
Generates a rectangular-wave-shaped drive signal to be
Compare with the approximated coil current.
Based on the result, the motor is driven at a constant current.
Then, the plurality of switch elements are individually turned on / off.
And a drive unit .

[0016]

According to the present invention, drive power is supplied to a plurality of phase coils of a brushless DC motor by a plurality of switch elements. The plurality of switch elements are individually turned on / off by a drive unit. A current detection resistor is connected in series to each of the plurality of switch elements . A driving unit configured to switch the switching element;
In synchronization with the operation, the voltage between the terminals of the plurality of current detecting resistors is changed.
By sampling and holding each pressure,
Approximately calculate the coil current for each phase of the motor.
Every 60 electrical degrees according to the detection signal from the magnetic pole detection element
Generates a rectangular-wave-like drive signal that changes to
And the coil current calculated approximately.
Based on the comparison result, the motor is driven at a constant current.
As described above, the plurality of switch elements are individually turned on / off.
I do.

[0017]

FIG. 1 is a circuit diagram showing an electric configuration of a motor driving device 31 according to one embodiment of the present invention.

The motor 32 has three phases and includes a stator having three coils 33, 34, and 35. The coils 33, 34, and 35 of each phase are connected to the U-phase, the V-phase, and the It is excited by the W-phase drive signals Iu, Iv, Iw. The motor 32 includes a rotor 36 made of a permanent magnet having a pair of magnetic poles. The motor 32 includes a Hall element or the like for detecting the rotation speed of the rotor 36, and includes a magnetic pole detection element 37 that outputs magnetic pole signals Hu, Hv, Hw for each phase.

The drive circuit 31 includes coils 33, 34, 35
The drive signals Iu, Iv, Iw of the U-phase, V-phase and W-phase
, Each of which supplies six transistors Q1 and Q
2, Q3, Q4, Q5, and Q6 are provided. Diodes D1 and D are connected in parallel with the transistors Q1 to Q6, respectively.
2, D3, D4, D5, and D6 are provided. The anodes of the diodes D1 to D6 are connected to the transistors Q1 to Q6, respectively.
And the drains of the transistors Q1 to Q3 are connected to the positive electrode of the DC power supply 38. Transistor Q
Sources of 1 to Q3 are connected to drains of transistors Q4 to Q6.

A resistor for detecting a phase current (hereinafter referred to as a resistor) Ru is connected between the sources of the transistors Q4 and Q5,
A resistor Rw is connected between the sources of the transistors Q5 and Q6. Sources of the transistors Q4 and Q6 are connected to sample and hold circuits 47 and 48, respectively. The source of the transistor Q5 is connected between the resistors Ru and Rw, and is connected to the negative electrode of the DC power supply 38 via the current detection resistor 65. Transistors Q1, Q4; Q
2, Q5; drive signals Iu, Iv, Iw of the U-phase, V-phase, and W-phase are output from respective connection points of Q3, Q6.

The magnetic pole detecting element 37 has a driving waveform pattern generating circuit (hereinafter referred to as a pattern generating circuit) 39 and a frequency / frequency
The signal is input to a voltage conversion circuit (hereinafter, referred to as a conversion circuit) 40. The output of the conversion circuit 40 is compared with command data from a speed command input unit 66 for inputting command data corresponding to a predetermined number of rotations of the motor 32 in a calculation unit 43, and is output to a multiplier 41 via a buffer 44. 42 respectively. The pattern generation circuit 39 outputs U-phase and W-phase drive signals Vu, Vw to the multipliers 41, 42 based on the output from the magnetic pole detection element 37, respectively.

The outputs of the multipliers 41 and 42 are inverted and added by the adder 46, respectively.
0, and the output of the adder 46 is input to the comparator 69. The outputs of the comparators 68 to 70 are supplied to the PWM circuits 52, 53, 5 via buffers 49, 50, 51, respectively.
4 respectively. Outputs of the PWM circuits 52 to 54 are respectively input to dead time circuits 55, 56, and 57 that generate a dead time described later. The output of each dead time circuit 55-57 is connected to each transistor Q1, Q
Drive signals U, V, W input to the gates of Q2 and Q3. The outputs of the dead time circuits 55 to 57 are inverted and input to the AND circuits 58, 59, 60, respectively. The outputs of the AND circuits 58 to 60 are output to the transistors Q4,
Drive signals EU, EV, input to the gates of Q5 and Q6,
EW.

The outputs of the sample and hold circuits 47 and 48 are input to the comparators 68 and 70, respectively, inverted and added by an adder 45. The output of the adder 45 is input to the comparator 69.

The voltage between the terminals of the current detecting resistor 65 is
It is input to the current control circuit 61. In the current control circuit 61, the inter-terminal voltage is inverted and input to the comparator 64, where it is compared with a reference potential from a power supply 63 that generates a predetermined reference potential. The output of the comparator 64 is input to the current limiting circuit 62. When the inter-terminal voltage exceeds the reference potential, the current limiting circuit 62 outputs a low-level current limiting signal. When the inter-terminal voltage is lower than the reference potential, a high-level current permission signal is output. The output of the current limiting circuit 62 is supplied to the AND circuits 58, 5
9 and 60. Outputs of the AND circuits 58 and 60 are input to the sample and hold circuits 47 and 48 as control signals for a sample / hold operation.

FIG. 2 is a waveform diagram for explaining the phase current detection operation during forward rotation of the motor 32 in this embodiment.

FIGS. 2A to 2C show the magnetic pole detecting element 37.
5 shows a detection signal for each phase from FIG.

FIGS. 2 (4) and 2 (5) show driving signals from the pattern generating circuit 39. FIG.

FIGS. 2 (6) to 2 (8) show the coil current for each phase of the motor 32. FIG.

The driving method of this embodiment is such that the voltage between the terminals of the resistors Ru and Rw is sampled and held in synchronization with the switching operation of each of the transistors Q1 to Q6, so that the coil current for each phase of the motor 32 is controlled. Is approximately obtained. In addition, a drive signal in the form of a rectangular wave that changes every 60 electrical degrees is generated by the detection signal from the magnetic pole detection element 37. The driving signal is compared with the approximated coil current, and the motor 32 is driven at a constant current based on the comparison result. In the present embodiment, the torque ripple based on the inductance of the coil is suppressed by such a driving method.

The detection signal H from the magnetic pole detection element 37
The drive signals Vu, Vw are generated by the pattern generation circuit 39 based on u, Hv, Hw. The speed command signal corresponding to the predetermined number of rotations of the motor 32 from the speed command input unit 66 is compared by the comparator 43,
42, the driving signals Vu and Vw are calculated. The calculation results of the multipliers 41 and 42 are output from the comparators 68 to 70 to the resistors R and R from the sample and hold circuits 47 and 48.
The operation is compared with the voltage between the terminals u and Rw. Comparator 68-
The output of 70 is converted into a PWM signal by PWM circuits 52 to 54, and is output by dead time circuits 55 to 57.
Dead time is added. Dead time circuit 55-5
7 outputs drive signals U,
V, W, or inverted and AND circuits 58-
After 60, drive signals EU, EV, EW for driving the transistors Q4 to Q6 are obtained. The AND circuits 58 to 6
0 is output to the sample and hold circuits 47 and 48,
A control signal CT defining the timing of the sampling operation and the holding operation of each of the sample and hold circuits 47 and
u, CTw.

That is, in the present embodiment, the voltage between the terminals of the phase current detecting resistors Ru and Rw is sampled and held by the sample and hold circuits 47 and 48, and the output of the sample and hold circuits 47 and 48 is used to output each transistor Q1. To Q6. The operation timings of the sample and hold circuits 47 and 48 are defined by drive signals EU and EW that define the switching operation of the transistors Q4 and Q6.

FIGS. 3 (1) to 3 (5) are time charts at the time of reverse rotation of the motor 32 according to the driving method of the motor 32 of this embodiment.

When the motor 32 rotates in the reverse direction, the same driving method as that of the inverter circuit 67 during the normal rotation is performed. Therefore, even when the motor 32 rotates in the reverse direction,
The same effect as the effect described at the time of the forward rotation can be achieved.

FIGS. 2 (9) to (13) show a motor 32 in a drive system in which a pattern generation circuit 39 generates drive signals Vu and Vw having a substantially sinusoidal waveform whose level changes stepwise at every 60 electrical degrees. 5 is a time chart at the time of forward rotation of the first embodiment.

FIGS. 3 (6) and (7) are time charts when the motor 32 rotates in the reverse direction in this driving method.

The drive signal V as shown in FIGS.
According to u and Vw, the coil currents Iu and I
“v” and “Iw” are waveforms in which the level changes stepwise every 60 electrical degrees regardless of whether the motor 32 is rotating forward or backward. Even with such a substantially sinusoidal drive signal, the same effect as in the above embodiment can be achieved.

[0037]

As described above, according to the present invention, an increase in the torque ripple of the motor can be prevented, and the quietness of the motor can be remarkably improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a motor driving device 31 according to an embodiment of the present invention.

FIG. 2 is a time chart for explaining the operation of the present embodiment when the motor 32 rotates forward.

FIG. 3 is a time chart for explaining the operation of the present embodiment when the motor 32 rotates in the reverse direction.

FIG. 4 is a circuit diagram of a driving device 1 according to the related art.

FIG. 5 is a time chart for explaining the operation of the conventional technique.

[Explanation of symbols]

 REFERENCE SIGNS LIST 31 drive device 32 motor 33, 34, 35 coil 38 DC power supply 39 pattern generation circuit 47, 48 sample and hold circuit 67 inverter circuit 68, 69, 70 comparator Ru, Rw phase current detection resistor

Claims (1)

(57) [Claims] 1. A plurality of switch elements for supplying drive power to each phase coil of a brushless DC motor having a plurality of phase coils, and a plurality of currents respectively connected to at least a part of the plurality of switch elements. A detection resistor and the magnetic pole detection for detecting a rotation speed of a rotor of the motor;
Element, in synchronization with the switching operation of the switch element,
Sample the voltage between terminals of multiple current detection resistors
By holding, the coil for each phase of the motor
Current from the magnetic pole detecting element.
A rectangular wave that changes every 60 electrical degrees depending on the detection signal
A drive signal is generated, and the drive signal and the approximate
And compared the coil current, based on the comparison result,
The plurality of switches are controlled so as to drive the motor at a constant current.
Brushless DC motor driving device, characterized in that it comprises Tsu a driving unit for switch elements individually on / off drive, the.