JP2001190084A - Driving circuit of motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the noise of a compact DC brushless motor used in a room or the like. SOLUTION: This driving circuit of a motor has a voltage control means that chops a DC power supply for efficiently generating ±supply voltages, and the output voltage of the voltage control means is applied as the supply voltage for a coil-driving circuit according to a speed signal from the motor. Also, a bias voltage corresponding to voltage being applied to the coil-driving circuit is applied to a Hall element, and the output of the Hall element is amplified for applying it to a motor coil, thus preventing the distortion of a current waveform in communication.

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 reducing the noise of a small DC brushless motor driven and used near a person indoors or the like.

[0002]

2. Description of the Related Art FIG. 4 is an example of a drive circuit diagram of a two-phase DC brushless motor used for a miniature fan or acoustic equipment which dislikes noise and noise. The Hall element 5 for detecting a magnetic pole position of a rotor magnet is shown in FIG. In this method, the output voltage waveform is sinusoidal, amplified by a winding drive circuit 8 including an amplifier, and a sinusoidal voltage called a linear drive is applied to the motor windings 3 and 4 to rotate at a command speed. The output of the frequency generator 2 that outputs a frequency proportional to the motor speed is used as a speed feedback signal, and the speed feedback signal is expressed as F / V
The DC voltage is converted by the conversion circuit 9, the input voltage of the Hall element is changed by the speed feedback signal by the bias circuit 10, the output voltage of the winding drive circuit 8 is controlled, and the rotation speed of the motor is kept constant. Reference numeral 26 denotes a ± power supply, and the midpoint is GND.
And

[0005] FIG. 5 shows an F / F with respect to the first example of FIG.
Voltage regulators 27 and 28 are output by V conversion circuit 9.
FIG. 9 is a drive circuit diagram of a second example in which the power supply voltage of the winding drive circuit 8 is controlled to maintain the rotation speed of the motor constant. FIG. 6 shows the operation of the above-described drive system, in which 6-a indicates the number of revolutions of the motor under rated load, overload, and light load conditions,
At the time of overload and light load, the rotation speed slightly changes from the rated rotation speed due to the load resistance characteristic by the control loop gain. 6-
b indicates an output voltage of the F / V converter 9. 6-c indicates a voltage input to the Hall element 5 in the circuit configuration of FIG.
d indicates a change in the output voltage of the Hall element 5.

[0004]

SUMMARY OF THE INVENTION The first problem shown in FIG.
In the linear drive system in which the speed is controlled by the bias voltage of the Hall element in the example of the above, in the case of a light load, the difference between the voltage applied to the motor winding and the power supply voltage is large. 6-e in FIG. 6 shows this state, in which the solid line indicates the level of the power supply voltage, and the broken line indicates the voltage waveform applied to the motor winding. Since the remaining voltage between the collector and the emitter of the transistor that directly drives the motor winding (difference voltage between the solid line and the dashed line of 6-e) is large, the power loss is large, causing the transistor to generate heat, and heat dissipation measures are required.

In the method of varying the applied voltage of the motor winding drive circuit 8 in FIG. 5, the voltage is changed as shown by a solid line by the dropper type voltage regulators 27 and 28 as shown by 6-f in FIG. And the voltage waveform applied to the motor windings 3 and 4 at light load becomes a rectangular waveform as indicated by the broken line 6-f, and the rise and fall of the conduction current become steep. . In addition, the current waveform of the motor winding is distorted due to the inductance component of the motor winding, which causes a torque ripple and a reduction in efficiency of the motor. It is a well-known fact that the voltage loss of the dropper type voltage regulator is large.

Further, in order to constitute a linear drive with a simplified circuit, a positive / negative ± power source 26 is required, and a device incorporating a DC brushless motor requires a dedicated power source and is often avoided. .

[0007]

SUMMARY OF THE INVENTION In a motor drive circuit according to the present invention, a power supply is required to solve the above-described problems based on a linear drive system in which a magnetic pole detection output is amplified to drive a motor winding. As for claim 1,
The power supply has voltage control means for efficiently generating ± DC power supply voltage by chopping the DC power supply, and controls the output voltage of the voltage control means in accordance with the speed signal from the motor to apply it as a winding drive circuit power supply voltage.

The positive and negative ± DC power sources to be generated select boosting or stepping-down according to the application. For generating a boosted power source, two sets of choke coils and transistors connected in series are provided in parallel with a single power source, and a DC power source is chopped by the two sets of transistors at the same time. Is stored in two sets of series-connected capacitors via two sets of diodes, and the midpoint between the two sets of capacitors and the midpoint connecting the collectors of the two sets of series-connected transistors is connected to a virtual GND. The positive and negative ± power supplies are obtained.

In order to generate a step-down power supply, two sets of diodes and transistors connected in series are provided in parallel with a single power supply, and a DC power supply is chopped by the two sets of transistors at the same time. Energize the choke coil,
Energy from the two sets of choke coils is stored in two sets of series-connected capacitors, and the midpoint of the two sets of capacitors and the midpoint of the two sets of diodes connected in series are defined as positive and negative ± GND as virtual GND. Configure so that power can be obtained.

In order to change the voltage waveform applied to the motor winding from a trapezoidal wave close to a rectangular wave to a sine wave, a bias voltage corresponding to the voltage applied to the winding driving circuit is applied to the rotor magnet. This is applied to a Hall element for detecting a magnetic pole position, amplifies the output of the Hall element, and applies it to the motor winding to prevent waveform distortion. The trapezoidal wave is obtained by adding the third harmonic to the basic sine wave. Conversely, the basic sine wave can be obtained by subtracting the third harmonic from the trapezoidal wave. A third harmonic component which is specialized for a three-phase motor and forms a trapezoidal wave by adding and combining trapezoidal motor winding applied voltage waveforms for three phases with a phase difference of 120 degrees is combined. Can be extracted. This third
Subtracts the second harmonic component from the trapezoidal wave and shapes it into a sine wave.
It is possible to set the motor winding applied voltage.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example in which a voltage control circuit according to the present invention is applied to a drive circuit of a two-phase DC brushless motor. The output of a Hall element 5 for detecting a magnetic pole position of a rotor magnet of a motor 1 is output by an operational amplifier 6 and a power transistor group 7. Amplified by the amplifying circuit 8 configured, the output voltage is applied to one side of the motor A and B-phase windings 3 and 4, and the other of the A and B-phase windings is generated by the voltage control circuit 25. Virtual GN
Connected to D.

A bias circuit 10 converts the output of a frequency generator 2 that outputs a frequency proportional to the speed of the DC brushless motor 1 to an input voltage of a Hall element 5 with an output of an F / V conversion circuit 9 that converts the output to a DC voltage. Negative feedback is applied.

The PWM pulse circuit 12 generates a PWM pulse proportional to the difference voltage between the output of the F / V conversion circuit 9 and the output of the rotation speed command voltage 11, and the step-down voltage control circuit 25
Is connected to the cathode of the light emitting diode of the photocoupler 13.

The photocoupler 13 of the step-down voltage control circuit 25
The PWM pulse circuit 1 is connected to the cathode of the light emitting diode.
The PWM pulse signal generated in step 2 is input and the DC power supply 1
4, the collector of the output transistor of the photocoupler 13 is connected to the + side of the DC power supply 14 via the resistor R1, and the emitter is connected to the-side of the DC power supply 14 via the resistor R2. The emitter of the PNP transistor 15 is connected to the + side of the DC power supply 14 and the base is connected to the photocoupler 13.
The collector is connected to one side of the choke coil 17 and the cathode of the diode 19. The emitter of the NPN transistor 16 is connected to the negative side of the DC power supply 14, the base is connected to the emitter of the photocoupler 13, and the collector is connected to one side of the choke coil 18 and the anode of the diode 20.

The other terminal of the choke coil 17 is connected to the positive electrode of the electrolytic capacitor 21, and the other terminal of the choke coil 18 is connected to the negative electrode of the electrolytic capacitor 22.
The plus side 23 and the minus side 24 of the generated ± power supply voltage are used. The negative electrode of the electrolytic capacitor 21, the positive electrode of the electrolytic capacitor 22, the anode of the diode 19, and the cathode of the diode 20 are connected to form a virtual GND.

FIG. 2 is a diagram for explaining the operation of the present invention.
2-a indicates the rotational speed of the motor in a load state.
−b indicates the output voltage of the F / V conversion circuit 9, and 2-c indicates the output voltage of the speed command voltage 11 and the differential voltage of the F / V conversion circuit 9.
This is an output pulse of the WM pulse circuit 12, and the pulse duty changes according to the load, and the ± voltage output of the step-down voltage control circuit 25 changes as 2-d. On the other hand, the Hall element 5
The input voltage becomes small at a light load by the bias circuit 10 and becomes large at an overload. As a result, the output voltage of the Hall element 5 changes according to the load as indicated by 2-e.

In 2-f, the solid line shows the output voltage of the step-down voltage control circuit 25, and the broken line shows the output voltage waveform of the motor winding drive circuit 8. As described above, in the present invention, since the voltage difference between the amplitudes of the voltage control circuit 25 and the motor winding drive circuit 8 is very small, the loss of the power transistor group 7 is small, the heat generation is low, and the need for heat radiation measures is eliminated.

The operation of the step-down voltage control circuit 25 is as follows. O of output transistor of photocoupler 13
N turns on the PNP transistor 15 and the NPN transistor 16, and charges the electrolytic capacitors 21 and 22 through the choke coils 17 and 18. When the output transistor of the photocoupler 13 is turned off, the PNP transistor 15 and the NPN transistor 16 are turned off, and the current energy stored in the choke coils 17 and 18 is charged to the electrolytic capacitors 21 and 22 through the diodes 19 and 20 as an induced voltage. You. This circuit configuration is of a chopping type and can easily generate a ± power source with a small loss. The ± power supply voltage becomes lower than the DC power supply voltage in accordance with the speed command voltage.

FIG. 3 shows an example in which the present invention is applied to a three-phase DC brushless motor, and the same effects as those of the above-described two-phase motor can be obtained. In the figure, U, V, and W indicate three-phase motor windings. The output of three Hall elements 5 for detecting the magnetic pole position of the rotor magnet of the motor 1 is composed of three sets composed of an operational amplifier 6 and a power transistor group 7. The output voltage is amplified by the amplifying circuit 8 of the motor U,
One side of the V and W phase windings is connected, and the other side of the U, V and W phase windings are collectively connected to a virtual GND of the DC power supply voltage generated by the boost voltage control circuit 29. Hall element 5 for detecting magnetic pole position of rotor magnet and amplifying circuit 8
Is almost the same as the circuit of FIG. 1 except that three sets are provided.
The output of the frequency generator 2 for detecting the speed of the motor is F / V
The voltage is converted by the conversion circuit 9 into a voltage. Reference numeral 29 denotes a configuration of a step-up voltage control circuit, which can generate a ± voltage higher than that of the power supply 14, and can increase the efficiency of the motor.

The structure of the boost voltage control circuit 29 is PNP
The emitter of the transistor 31 is connected to the + side of the DC power supply 14 via the Coke coil 33, and the emitter of the NPN transistor 32 is connected to the-side of the DC power supply 14 via the Coke coil 34. To the NPN transistor 3
2 and the emitter of the photocoupler 13 are connected to each other, the collector of the PNP transistor 31 and the collector of the NPN transistor 32 are connected to the virtual GND,
The anode of the diode 35 is connected to the emitter of the PNP transistor 31, the cathode of the diode 35 is connected to the positive electrode of the electrolytic capacitor 37 and the output terminal 23, and the emitter of the NPN transistor 32 and the cathode of the diode 36 are connected
The anode of the diode 36 is connected to the negative electrode of the electrolytic capacitor 38 and the output terminal 22, and the output terminals 23 and 22
A ± DC power supply is configured.

The operation of the boost power supply control circuit 29 is as follows. ON of output transistor of photocoupler 13
The PNP transistor 31 and the NPN transistor 3
2 is turned on, and current flows through the yoke coils 33 and 34, but the electrolytic capacitors 37 and 38 are not charged. Next, when the output transistor of the photocoupler 13 is turned off, an induced voltage is generated by the current energy of the yoke coils 33 and 34, and the electrolytic capacitors 37 and 38 are charged via the diodes 35 and 36, and the output terminals 22 and 23
, A ± voltage is output around the virtual GND. This voltage becomes higher than the power supply voltage according to the speed command voltage.

FIGS. 7 and 8 are simplified versions of the above-described voltage control circuit, which are constructed in a step-down mode and a step-up mode, respectively.

FIG. 9 is a block diagram of a motor winding driving circuit for shaping a voltage waveform applied to the motor winding from a trapezoidal wave close to a rectangular wave into a sine wave. This is a synthesis circuit that performs negative feedback on the phase. In FIG. 10, 10-a is the output voltage of the three-phase motor winding drive circuit 8, 10-b is the output voltage waveform of the amplifier 6 of the synthesis circuit 50, and the three-phase electric voltage applied to the motor winding. Corner 120
It is obtained by adding the trapezoidal voltage waveforms of the phase difference. 10
The conduction fundamental frequency of the U-phase, V-phase and W-phase voltage waveforms of -a is
It is determined from the motor speed and the number of magnetic poles. It can be seen that 10-b is the third harmonic with respect to the basic conduction frequency. Since the third harmonic is generated by the above configuration, it is also synchronized with the voltage applied to the motor. By negatively feeding back the generated third harmonic to the input of the amplifier 6 of the motor winding drive circuit 8 of each phase, the third harmonic contained in the trapezoidal wave of each phase is removed. It is shaped into a sinusoidal voltage waveform as shown by c, and can be applied to the motor windings (U, V, W).

[0024]

(1) In the motor drive circuit configuration according to the present invention, it is possible to apply a nearly sinusoidal trapezoidal voltage waveform to the motor windings, thereby significantly reducing noise and noise generated during commutation. A motor can be provided. Further, even if the speed or load of the motor changes, the temperature rise of the transistor of the motor drive circuit can be suppressed. (2) In addition, a ± power supply voltage that also serves as a motor control can be generated from a DC power supply with a simplified circuit configuration, and both step-up and step-down can be performed according to the purpose. It is general-purpose with a power supply and is inexpensive. (3) Not only single-phase, two-phase motors, and three-phase motors but also all DC brushless motors can be used in combination with a step-up / step-down control circuit to expand the applicable range, and the same effects as described above can be obtained. (4) The voltage control circuit and the motor winding drive circuit can be configured at a low cost by being integrated into an IC, and are most suitable for a fan motor and an office machine motor used indoors.

[Brief description of the drawings]

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

FIG. 2 is an operation explanatory diagram of a drive circuit of a two-phase DC brushless motor according to the present invention.

FIG. 3 is a drive circuit configuration diagram of a three-phase DC brushless motor according to the present invention.

FIG. 4 is a drive circuit configuration diagram of a conventional two-phase DC brushless motor.

FIG. 5 is a drive circuit configuration diagram of another example of a conventional two-phase DC brushless motor.

FIG. 6 is a diagram illustrating the operation of a drive circuit in a conventional two-phase DC brushless motor.

FIG. 7 is a step-down voltage control circuit according to the present invention.

FIG. 8 is a step-up voltage control circuit according to the present invention.

FIG. 9 is a configuration diagram of a winding drive circuit of the three-phase DC brushless motor according to the present invention.

FIG. 10 is an explanatory diagram of a winding drive circuit of a three-phase DC brushless motor according to the present invention.

[Explanation of symbols]

1: DC brushless motor 2: frequency generator 3: A-phase winding of two-phase motor 4: B-phase winding of two-phase motor 5: Hall element 6: Amplifier 7: Power transistor group 8: Motor winding drive circuit 9 : F / V conversion circuit 10: Hall element bias circuit 11: Speed command voltage 12: PWM pulse generation circuit 13: Photocoupler 14: Single DC power supply 15: PNP transistor 16: NPN transistor 17, 18: Choke coil 19, 20 : Diode 21, 22: Electrolytic capacitor 23: + Voltage output 24: -Voltage output 25: Step-down voltage control circuit 26: ± Power supply 27, 28: Voltage regulator 29: Boost voltage control circuit 30: Level shift circuit 31: PNP transistor 32 : NPN transistors 33, 34: Choke coils 35, 3 : Diodes 37, 38: Electrolytic capacitors 40, 46: PNP transistors 41, 47: Diodes 42, 45: Choke coils 43, 44, 48, 49: Electrolytic capacitors 50: Synthetic circuit Vcc: Hall element bias voltage r: Configures an amplifier Resistance 2-a: Motor rotation speed 2-b: F / V conversion circuit output 2-c: PWM pulse duty 2-d: Step-down voltage control output 2-e: Hall element output voltage 2-f: Step-down 6-a: Motor rotation speed 6-b: F / V conversion circuit output 6-c: Hall element input voltage 6-d: Hall element output voltage 6-e : Power supply voltage and motor winding applied voltage 6-f: Voltage regulator output and motor winding applied voltage 10-a: Output voltage of three-phase motor winding drive circuit Voltage waveform 10-b: Output voltage waveform of composite circuit 10-c: Output voltage waveform of three-phase motor winding drive circuit after waveform correction

Claims (7)

[Claims] 1. A circuit for driving a motor winding of a DC brushless motor comprising a magnetic pole sensor for detecting a magnetic pole position of a rotor magnet and a motor winding driving circuit for energizing a motor winding in both directions (bipolar). A voltage control means for generating a positive and negative power supply voltage for the virtual GND for the motor winding drive circuit by chopping a power supply, and outputting an output voltage of the voltage control means controlled according to a speed command voltage to the winding; A motor drive circuit, which is applied as a power supply voltage for a drive circuit, has one side of each phase of a motor winding connected to a virtual GND, and is configured to rotate at a specified speed. 2. The voltage control means according to claim 1, wherein two sets of diodes and a switching element connected in series are connected to said DC
A second diode is provided in parallel with the power supply, and the + side of the DC power supply is connected to the cathode side of the first diode via the first switching element, and the-side of the DC power supply is connected to the second diode via the second switching element. Connected to the anode side of
One end of the choke coil is connected to the cathode of the first diode, the other end is connected to the positive electrode of the first capacitor, and one end of the second choke coil is connected to the anode of the second diode, and the other end is connected to the first diode. Connected to the negative electrode of the first capacitor, the negative electrode of the first capacitor, the positive electrode of the second capacitor, the anode of the first diode, and the cathode of the second diode. 2 is connected to the middle point voltage (virtual GND), the positive electrode of the first capacitor is output as a positive voltage, and the negative electrode of the second capacitor is output as a positive voltage.
A step-down voltage control circuit for a DC power supply having an electrode as a negative voltage output is configured, and an output voltage of the voltage control circuit controlled according to a speed command signal is applied as a power supply voltage for the winding drive circuit, and is designated. A motor drive circuit characterized by being configured to rotate at a constant speed. 3. The voltage control means according to claim 1, wherein two sets of choke coils and a switching element connected in series are provided in parallel with the DC power supply, and one side of the first choke coil is connected to the + side of the DC power supply. The other is connected to one side of the first switching element, one side of the second choke coil is connected to the negative side of the DC power supply, the other side is connected to one side of the second switching element, and the first diode is connected. Is connected to the connection point of the first choke coil and the first switching element, the cathode is connected to the positive electrode of the first capacitor, and the cathode side of the second diode is connected to the second choke coil and the second switching element. At the switching element connection point, the anode is connected to the negative electrode of the second capacitor, and the negative side of the first capacitor and the positive electrode of the second capacitor are connected to the first switching element and the second electrode. 2, the connection point of the first capacitor and the second capacitor is a midpoint voltage (virtual GND), the positive electrode of the first capacitor is a positive voltage output, and the negative electrode of the second capacitor is a negative voltage output. A boost voltage control circuit for a DC power supply having an electrode as a negative voltage output is configured, and an output voltage of the voltage control circuit controlled according to a speed command signal is applied as a power supply voltage for the winding drive circuit, and the voltage is specified. A motor drive circuit characterized by being configured to rotate at a constant speed. 4. The voltage control means according to claim 1, wherein a diode and a switching element connected in series are provided in parallel with the DC power supply, and the cathode side of the diode is connected to the positive side of the DC power supply via the switching element and the anode is connected to the anode. Side is connected to the negative side of the power supply, one side of the choke coil is connected to the cathode of the diode, the other side is connected to the positive electrode of the first capacitor, and the negative side of the first capacitor and the positive electrode of the second capacitor. , The negative electrode of the second capacitor is connected to the negative side of the DC power supply, the node between the first and second capacitors is connected to the midpoint voltage (virtual GND), and the positive electrode of the first capacitor is connected to A step-down voltage control circuit for a DC power supply having a positive voltage output and a negative electrode of the second capacitor as a negative voltage output, wherein the output voltage of the voltage control circuit controlled according to the speed command signal is A motor drive circuit characterized in that the motor drive circuit is configured to be applied as a power supply voltage for the winding drive circuit and to rotate at a specified speed. 5. The voltage control means according to claim 1, wherein a choke coil and a switching element connected in series are provided in parallel with the DC power supply, and one side of the choke coil is connected to the + side of the DC power supply. The other side is connected to the switching element, the other side of the switching element is connected to the negative side of the power supply, the anode of the diode is connected to the connection point between the choke coil and the switching element, and the cathode side is connected to the + electrode of the first capacitor. Connecting the negative electrode of the first capacitor to the positive electrode of the second capacitor, connecting the negative electrode of the second capacitor to the negative electrode of the DC power source, and connecting the first capacitor and the second capacitor. DC where the point is a midpoint voltage (virtual GND), the positive electrode of the first capacitor outputs a positive voltage, and the negative electrode of the second capacitor outputs a negative voltage.
A boost voltage control circuit for a power supply is configured, and an output voltage of the voltage control circuit controlled according to a speed command signal is applied as a power supply voltage for the winding drive circuit, and the motor is rotated at a specified speed. A motor drive circuit characterized by the following. 6. The method according to claim 1, wherein a Hall effect element is used for the magnetic pole position sensor, and a bias voltage corresponding to a voltage applied to the winding drive circuit is applied to the Hall element. And amplifying the output of the Hall element and applying the amplified output to a motor winding.
A motor drive circuit according to claim 1. 7. A magnetic pole sensor for detecting a magnetic pole position of a rotor magnet of a three-phase DC brushless motor, and a motor winding drive circuit for amplifying an output voltage of the magnetic pole sensor and energizing a motor winding in both directions (bipolar). In this case, by adding the amplifier outputs for three phases in the motor winding drive circuit,
Using the motor winding drive voltage waveform as the fundamental frequency,
A motor winding drive circuit for detecting a second harmonic and performing negative feedback to each of the three-phase amplifier inputs.