JPH0746886A - Motor drive circuit - Google Patents

Abstract

PURPOSE:To obtain a power system circuit having simple circuitry by constituting an H bridge such that a current is fed through a single phase induction motor in one direction by transistors applied, respectively, with a pulse signal and a PWM signal and a current is fed in reverse direction for next different active state. CONSTITUTION:A comparator 9 is provided with an inversion unit 71 on the input side thereof and produces a pulse waveform having an active state generating time shifted by a half period of the sine wave from that of a comparator 10. Since a PWM signal is applied to the gate of a Tr5 when the gate of a power MOSFET(Tr)2 is turned ON, current flows through a capacitor motor (CM)6 from the left to the right. When the Tr4 is turned ON, current flows through the motor from the right to the left. Since PWM signals are fed to the gate terminals of the Tr3 and Tr5, sine wave current flows through the CM6 and thereby a smooth motor circuit is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a motor drive circuit,
In particular, it relates to a drive circuit for a single-phase induction motor such as a capacitor motor.

[0002]

2. Description of the Related Art FIG. 6 shows a conventional motor drive circuit. As shown in the figure, the motor drive circuit includes an AC power supply 14, a diode bridge 15, a capacitor 16, a 6-phase pulse generator 24, a power transistor (hereinafter referred to as "power MOSF").
25 to 30), and a three-phase induction motor 31.

AC power supply 14 and diode bridge for rectification
The DC power source 1 is composed of 15 and the smoothing capacitor 16, and the three-phase inverter is composed of the power MOSFETs 25 to 30. Further, the gate signals of the power MOSFETs 25 to 30 are supplied from the 6-phase pulse generator 24.

FIG. 7 shows the gate signal waveforms of the power MOSFETs 25-30. Signals are output from the 6-phase pulse generator 24 at timings of 6 phases, a gate voltage is applied to the power MOSFETs 25 to 30, and the power MOSFETs 25 to 30 are made conductive. Then, as shown in the voltage waveform of the three-phase induction motor of FIG. 8, a simple three-phase AC voltage is applied to the three-phase induction motor.

FIG. 9 shows a detailed circuit diagram of the 6-phase pulse generator 24. The 6-phase pulse generator 24 includes a pulse oscillation circuit 32,
6-phase ring counter 33, output pulse width setting voltage 34,
It is composed of timer circuits 35 to 40, and a 6-phase reference signal is generated by applying a clock signal of 6 times the 3-phase AC frequency to the 6-phase ring counter 33 from the pulse oscillating circuit 32 to generate an output pulse width setting voltage 34. The output pulse corresponding to the data from is obtained from the timer circuits 35-40.

FIG. 10 shows a second conventional control example for applying a sinusoidal three-phase AC voltage to the three-phase induction motor 31. This uses a sine wave PWM circuit 41 shown in FIG. 10 instead of the 6-phase pulse generator 24. It has an output pulse width setting voltage 34, a pulse oscillation circuit 32, a counter 35, and memories 36 to 38. , Digital / analog converters 39 to 41, a triangular wave generator 8 and comparators 42 to 47.

The frequency of the pulse oscillation circuit 32 (proportional to the three-phase AC frequency) is controlled by the output pulse width setting voltage 34, and the output of the ring-counting counter 35 is input to the addresses of the memories 36 to 38. Generates a sine wave by supplying the three-phase sine wave digital data built in to the digital-analog converters 39-41, and compares this sine wave with the output waveform of the triangular wave generator 8 by the comparators 42-47. Then, FIG.
The sine wave PWM waveform shown in is output.

[0008]

In this conventional motor drive circuit, since the three-phase induction motor is used, the motor windings are required for three phases, the shape is large and the wiring is complicated, and the power consumption is high. Six transistors are required and a control circuit for six phases is required.

To obtain a sine wave PWM waveform,
Since a counter of about 256 counts, a memory of about 256 × 8 bits, and a digital-analog converter of about 8 bits are required, there is a drawback that the control circuit becomes complicated.

Therefore, an object of the present invention is to provide a motor drive circuit using a single-phase induction motor and having a simple control circuit configuration.

[0011]

In order to achieve the above-mentioned object, the present invention provides a series connection body of first and second transistors, a series connection body of third and fourth transistors, and two series connection bodies. A connection body is arranged in parallel with each other, and a single-phase induction motor having both ends connected to a connection point of the first and second transistors and a connection point of the third and fourth transistors, and an active ( A pulse generator that generates two pulse signals that do not overlap with each other in a time period in which the (active) state is held, and a pulse generator P that generates two pulse width modulation signals that are respectively activated corresponding to the active states of the two pulse signals.
A WM generator, and when one of the pulse signals is in an active state, the transistor to which the pulse signal is applied and the transistor to which the pulse width modulation signal is applied are
A motor having a structure in which a current flows in one direction through the single-phase induction motor and a current flows in the opposite direction to the single-phase induction motor when the other pulse signal is in an active state. A drive circuit is provided.

Further, in the present invention, the PWM generator comprises a sine wave generating circuit, a triangular wave generating circuit, and a comparing means for comparing the amplitudes of the output signals of the sine wave generating circuit and the triangular wave generating circuit. A drive circuit is provided.

Further, the present invention comprises an AC power supply, a rectifier circuit for generating a DC power supply from the AC power supply, and a full-wave rectification circuit for rectifying the AC power supply, wherein the PWM generator is the full-wave rectifier. Provided is a motor drive circuit including a circuit, a triangular wave generation circuit, and a full-wave rectification circuit and a comparison unit that compares the amplitudes of output signals of the triangular wave generation circuit.

The present invention also provides a motor drive circuit, wherein the triangular wave generating circuit comprises a triangular wave amplitude varying circuit for varying the amplitude of the triangular wave signal according to the output value of a generator provided in the single-phase induction motor. To do.

[0015]

In the motor drive circuit of the present invention, an H-bridge is constructed by using four transistors and a single-phase induction motor, and the pulse generator generates two pulses that do not overlap with each other in their active state holding times. A signal is output, a pulse width modulation signal is output from the PWM generator when the pulse signal is in the active state, and these four control signals of the pulse signal and the pulse width modulation signal are applied to the control terminals of the respective transistors. ing.

The transistor to which the pulse signal is applied and the transistor to which the pulse width modulation signal is applied are
The H-bridge type is configured so that current flows in one direction through the single-phase induction motor and reverse current flows in the single-phase induction motor during the next different activation states. As a result, the power system circuit of the motor drive circuit can be realized with a simple circuit configuration.

Further, the PWM generator preferably comprises a sine wave generating circuit, a triangular wave generating circuit and a comparing means.

Further, by obtaining the sine wave from the AC power source, the sine wave generating circuit can be constructed by a simple circuit.

Further, by providing the triangular wave amplitude varying circuit, it becomes possible to keep the rotational speed of the induction motor constant with respect to the load variation.

[0020]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a motor drive circuit showing an embodiment of the present invention.

The source terminal of the power MOSFET 2 and the drain terminal of the power MOSFET 3 are connected to each other, and the power MO
The SFETs 4 and 5 are connected in the same manner, the capacitor motor 6 is arranged between the respective connection points, and both ends of the capacitor motor 6 are connected to the connection points, respectively, and the power MOSFE is connected.
The T2 to 5 and the capacitor motor 6 constitute an H-bridge type power system circuit.

Then, the positive voltage of the DC power supply 1 is converted to the power MO.
Apply to the drain terminal of SFET2,4, power MOS
The source terminals of the FETs 3 and 5 are connected to the GND potential.

The output terminal of the sine wave generator 7 is connected via the inverter 71 to the non-inverting input terminal of the comparator 9, the non-inverting input terminal of the comparator 10, the inverting input terminal of the comparator 12, and the comparator. Connected to 4 of 13 non-inverting input terminals.

The inverting input terminals of the comparators 9 and 10 are connected to the output terminal of the triangular wave generator 8, and the non-inverting input terminal of the comparator 12 and the inverting input terminal of the comparator 13 are connected to the GND potential. The output terminals of the comparators 9, 10, 12, 13 are connected to the gate terminals of the power MOSFETs 3, 5, 4, 2, respectively.

Next, the operation of the present invention will be described. The sine wave output from the sine wave generator 7 and the triangular wave output from the triangular wave generator 8 are compared by comparators 9 and 10.

FIG. 2 shows input / output waveforms of the comparator 10. If the output voltage of the sine wave generator 7 is higher than the output voltage of the triangular wave generator 8, the comparator 10 outputs a voltage, and thus a voltage having a pulse waveform as shown in FIG. 2 is output. The output terminal of the comparator 9 has an inverter on the input side.
Since 71 is arranged, a pulse waveform in which the generation time of the active state deviates from the pulse waveform of the comparator 10 by a half cycle of the sine wave is output. These pulse waveforms are PWM waveforms whose duty changes according to the voltage of the sine wave.

FIG. 3 shows the gate voltage waveforms of the power MOSFETs 2 to 5 and the voltage / current waveforms of the capacitor motor 6. To the gate terminals of the power MOSFETs 2 and 4, a positive potential pulse waveform voltage having the same cycle as that of the sine wave generator 7 generated by the comparators 12 and 13 is applied so that their active states do not overlap. . On the other hand, power M
A PWM waveform is given to the gate terminals of the OSFETs 3 and 5.

Since the PWM signal is applied to the gate of the power MOSFET 5 when the gate of the power MOSFET 2 is ON, a motor current flows to the capacitor motor 6 from left to right in the drawing of FIG.
When the OSFET4 is ON, the motor current flows from the right to the left in the figure. Since the PWM signal is applied to the gate terminals of the power MOSFETs 3 and 5, a sinusoidal current flows through the capacitor motor 6 and smooth motor rotation is obtained.

FIG. 4 shows a second embodiment of the present invention. First
The same components as those in the embodiment of FIG.

In the figure, a DC power supply 1 is constituted by an AC power supply 14, a diode bridge 15 for full-wave rectification, and a smoothing capacitor 16. On the other hand, full-wave rectification is configured from the AC power supply 14 via the diodes 17 and 18,
Connect resistor 19 and resistor 20 in series from the cathode terminal of 18,
The connection point of the resistors 19 and 20 is connected to the non-inverting input terminal of the comparator 10, and the inverting input terminal of the comparator 10 is supplied with the output voltage from the triangular wave generator 8.

The other end of the resistor 20 is connected to the base terminal of the NPN transistor 21, the emitter terminal of the transistor 21 is connected to GND, and the collector terminal is connected to the power supply via the resistor. Further, the collector terminal is connected to the clock input terminal of the T-type flip-flop 50.

The Q output terminal of the T-type flip-flop 50 is 2
The input of the input AND gate 22 is connected to the gate terminal of the power MOSFET 4, and the inverted Q output terminal is connected to the input of the 2-input AND gate 23 and the gate terminal of the power MOSFET 2. The other input terminals of the AND gates 22 and 23 are connected to the output terminal of the comparator 10, and the output terminals of the AND gates 22 and 23 are connected to the gate terminals of the power MOSFETs 3 and 5, respectively.

The operation of the second embodiment will be described. By full-wave rectifying the voltage of the AC power supply 14 with the diodes 17 and 18, a divided full-wave rectified waveform is obtained at the connection point of the resistors 19 and 20. By comparing the voltage of this full-wave rectified waveform and the output voltage of the triangular wave generator 8 with the comparator 10,
A PWM signal with variable duty is created.

The transistor 21 outputs a positive pulse waveform having the same period as the full-wave rectified waveform by the applied voltage of the full-wave rectified waveform. The output of the T-type flip-flop 50 is repeatedly inverted by the application of this pulse waveform, and the AND gates 22 and 23 are ORed with the PWM signal to generate the gate signal of the power MOSFET. This gate signal has the same signal waveform as that shown in FIG. 3, which gives a sinusoidal current to the capacitor motor 6.

Generally, the rotation speed of the induction motor is determined by the input AC voltage, the input AC frequency and the load torque of the induction motor. However, in the capacitor motor, the frequency is controlled by the capacitor with the exciting current for phase advance fixed. Is not suitable for. Therefore, the rotational speed of the capacitor motor 6 needs to be controlled by varying the input AC voltage when the load torque cannot be predicted due to the load fluctuation.

As a method of controlling this input AC voltage,
When a generator (tacho generator) is connected, the output voltage of the triangular wave generator 8 is lowered when the input AC voltage does not reach the desired voltage, and when the input voltage is higher than the desired voltage, the output of the triangular wave generator 8 is increased. It is conceivable to increase the voltage to change the duty of the PWM waveform output by the comparator 10 as shown in FIG. 2 and control the voltage applied to the capacitor motor 6.

FIG. 5 shows a variable amplitude circuit for the triangular wave output in the triangular wave generator.

The cathode terminal of the constant voltage diode 102 is connected to the DC power source 101, and the anode terminal is connected to G via the resistor 103.
Connect to ND. The anode terminal is connected to the base terminal of the PNP transistor 105, the emitter terminal of the transistor 105 is connected to the power supply via the resistor 104, and the collector terminal is connected to GND via the capacitor 106.

The constant voltage diode 102, the resistors 103 and 104, and the transistor 105 constitute a constant current circuit, and a triangular wave is generated by charging the capacitor 106 with a constant current.

The collector terminal of the transistor 105 is also connected to the inverting input terminal of the comparator 108 via the delay circuit 107 composed of, for example, a resistor and a capacitor, and is also connected to the output terminal of the comparator 108. The non-inverting input terminal of the comparator 108 is connected to the DC generator 110 via the adjustment variable resistor 109. Here, the output type of the comparator 108 is an open collector type.

The voltage corresponding to the rotation speed of the electric motor is a DC generator.
The voltage generated by the comparator 110 is divided by the adjustment variable resistor 109, and if the triangular wave voltage is larger than the divided voltage, the comparator 10
The output of 8 goes low and discharges capacitor 106. The discharge time of the capacitor 106 is set by the delay circuit 107, and the discharge ends when the voltage at the non-inverting input terminal becomes larger than the voltage at the inverting input terminal.

As a result, the amplitude of the triangular wave voltage changes according to the output voltage of the DC generator 110, and the comparator 10
The duty of the PWM waveform is changed, the voltage applied to the capacitor motor 6 is controlled, and the rotation speed of the electric motor is kept constant against the load change.

When the load fluctuation can be ignored, such as with an electric fan or fan, the output voltage of the triangular wave generator 8 and the rotational speed are preset to keep the rotational speed of the induction motor constant. be able to.

In the embodiment according to the present invention, a conventional gate counter of about 256, three memories of about 256 × 8 bits, and three digital / analog converters of about 8 bits are required in the gate class. It becomes possible to replace with several ICs. Therefore, according to the present invention, a motor drive circuit in which the control system circuit is significantly reduced is used as a one-chip power MO.
It becomes easy to use an SIC or the like, and by implementing the IC, it is possible to improve the controllability due to the wiring length between the control system circuit and the power system circuit and to downsize the device.

[0046]

As described above, according to the present invention, a single-phase induction motor typified by a capacitor motor is used, and the motor winding has one phase of the main winding and one phase of the auxiliary winding for the advance current. Since they are compatible with each other, the size can be reduced, wiring can be facilitated, and the number of power transistors can be reduced from 6 to 4. Also in the control system circuit, there is an effect that the sine wave generating circuits for three phases can be reduced to one phase.

Further, by greatly reducing the control circuit and the power system circuit, one-chip IC can be easily realized, and the performance of noise resistance or crosstalk resistance due to the wiring length can be improved. .

Furthermore, by obtaining the sine wave required to generate the PWM signal from the AC power supply, the sine wave generation circuit can be simplified, which contributes greatly to the achievement of IC. Further, by providing the triangular wave amplitude variable circuit, the rotation speed of the electric motor can be kept constant with respect to the load fluctuation of the electric motor, and the application range of the motor drive circuit can be expanded.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a motor drive circuit showing an embodiment of the present invention.

2 is an input / output waveform of the comparator of FIG.

3 is a voltage waveform of each gate of the power MOSFET of FIG. 1 and a current / voltage waveform of a motor.

FIG. 4 is a circuit diagram of a motor drive circuit showing a second embodiment of the present invention.

FIG. 5 is a triangular wave amplitude variable circuit.

FIG. 6 is a circuit diagram of a motor drive circuit showing a conventional example.

FIG. 7 is a gate signal waveform of a power MOSFET in a conventional example.

FIG. 8 is a voltage waveform of a three-phase induction motor in a conventional example.

FIG. 9 is a detailed circuit diagram of a 6-phase pulse generator in a conventional example.

FIG. 10 is a circuit diagram of a sine wave PWM circuit that replaces the conventional 6-phase pulse generator.

11 is a voltage waveform of each part in the sine wave PWM circuit of FIG.

[Explanation of symbols]

 1 DC power supply 2-5 Power MOSFET 6 Capacitor motor 7 Sine wave generator 8 Triangle wave generator 9-10 Comparator 11 PWM generator 12-13 Comparator 14 AC power supply 15 Diode bridge 16 Capacitor 17-18 Diode 19-20 Resistance 21 Transistor 22-23 AND gate 24 6-phase pulse generator 25-30 Power MOSFET 31 Three-phase induction motor

Claims (4)

[Claims] 1. A series connection body of first and second transistors, a series connection body of third and fourth transistors, and two series connection bodies are arranged in parallel with each other, and the first and second , A single-phase induction motor having both ends connected to the connection point of the transistor and the connection point of the third and fourth transistors, and two pulse signals that do not overlap with each other in the time that the active state is maintained. And a PWM generator that generates two pulse width modulation signals that are respectively activated in response to the active states of the two pulse signals, and one pulse signal is in the active state. At this time, the transistor to which the pulse signal is applied and the pulse width modulation signal are applied to the transistor so that current flows in one direction through the single-phase induction motor and the other pulse signal. The motor drive circuit is characterized in that a reverse current flows through the single-phase induction motor when the signal is active. 2. The PWM generator comprises a sine wave generating circuit, a triangular wave generating circuit, and comparing means for comparing the amplitudes of the output signals of the sine wave generating circuit and the triangular wave generating circuit. The motor drive circuit according to claim 1. 3. An AC power supply, a rectifier circuit for generating a DC power supply from the AC power supply, and a full-wave rectifier circuit for rectifying the AC power supply, wherein the PWM generator includes the full-wave rectifier circuit and a triangular wave. 2. The motor drive circuit according to claim 1, wherein the motor drive circuit comprises a generation circuit and a comparison means for comparing the amplitudes of the output signals of the full-wave rectification circuit and the triangular wave generation circuit. 4. The triangular wave generating circuit comprises a triangular wave amplitude varying circuit for varying the amplitude of the triangular wave signal according to the output value of a generator provided in the single-phase induction motor. 3. The motor drive circuit according to item 3.