JP3234628B2 - Drive circuit for three-phase brushless 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 drive circuit for a three-phase brushless motor for driving a fan for an air conditioner room, a fan for a gas water heater, etc., and more particularly to a main circuit switching element and its control circuit having a monolithic structure. The present invention relates to a switching noise removing circuit suitable for removing generated noise.

[0002]

2. Description of the Related Art A three-phase brushless motor is a type of DC motor having three-phase windings of U, V, and W and driven by an electronic circuit. Device, June 1990, 85
As shown in FIG. 2, the upper arm circuit serving as a source switch and the lower arm circuit serving as a sink switch have a totem pole configuration, and the totem pole circuit has one phase to drive three phases. It is composed of a circuit.

Normally, a three-phase brushless motor rotates the motor by detecting the position of the rotor with a hall element built in the motor and sequentially turning on and off the switching elements of each phase according to the detection signal. In order to change the number of revolutions, the DC applied voltage is changed. However, in the conventional technique, instead of changing the DC voltage, a commercial 100 V rectified voltage is directly applied, and the upper or lower arm is applied with a DC applied voltage by a pulse width modulation signal. The variable speed control is performed by turning on and off. In this case, the motor speed is proportional to the average value of the pulse width modulated DC applied voltage.

The pulse width modulation signal is obtained by comparing a deviation between a motor speed signal and a speed command signal with a triangular wave signal, thereby controlling the motor speed according to the speed command signal. By making these drive circuits monolithic by dielectric isolation technology, they can be built into the motor.

[0005]

According to the prior art, when a signal from a Hall element incorporated in a motor is input into a monolithic chip, the detection signal is inverted by switching noise generated from a main circuit. To avoid this, an external circuit for converting the Hall element signal into a logic signal is indispensable.

An object of the present invention is to provide a circuit for removing noise received by a Hall element signal in order to eliminate the need for the external circuit.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to amplify and remove a weak signal from a Hall element by a circuit comprising a differential amplifier and a capacitor, and further synchronize the signal with the switching of a main circuit element to obtain a high signal. By determining whether the signal is low or low, it is possible to prevent inversion of the signal due to main circuit switching noise.

[0008]

The circuit including the differential amplifier and the capacitor operates to remove noise generated between the Hall element and the wiring connecting the circuit.

On the other hand, switching of the main circuit elements occurs during a phase switching operation according to a motor rotor position detection signal and during a chopping operation using a pulse width modulation signal.

At the time of the former phase switching operation, whether the position detection signal is high or low is determined in synchronization with the rising or falling edge of the internal clock synchronized with the triangular wave signal for generating the pulse width modulation signal. Is switched by the signal after the determination, so that it is not affected by the switching noise.

In the latter chopping operation, whether the position detection signal is high or low is determined in synchronization with the rising and falling edges of the pulse width modulation signal, so that the switching noise is not affected as in the former case.

That is, since the position detection signal is determined to be high or low by a signal obtained by logically ORing both edges of the internal clock and the pulse width modulation signal, the influence of the main circuit switching noise is prevented beforehand. Can be prevented.

[0013]

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, a self-extinguishing element (IGB
T, bipolar transistor, GTO, MOS-FET
Output switching element was used etc.) 6 is connected to a three-phase brushless motor 19, further, a commercial 100V AC power source is converted more DC to DC converter 2 power supply which was smooth direct current voltage by the smoothing capacitor 3 Connected to.

Next, a control circuit of the output switching element will be described.

First, the signal of the speed command oscillator 22 is removed from noise by the decision unit 9 and input to the phase comparator 15.

Next, the output of the speed detecting coil 21 for detecting the speed of the motor is input to the detector 18 to detect a speed signal.

Then, the speed signal and the speed command signal are compared in phase by a phase comparator 15 and are compared with the operational amplifier 12.
And a triangular wave signal 24 to a comparator 1
A pulse width modulated signal is generated by comparing with one.

On the other hand, the output signal of the Hall element 20 for detecting the position of the rotor magnetic pole of the motor is converted to a differential amplifier 1 with a filter.
It is amplified by 0 and input to the decision unit 9.

The judgment timing is as follows. A clock signal is extracted from the triangular wave and the clock generator 13, and a logical OR of the signal and the edge of the pulse width modulation signal is generated by the edge synthesizer 23, and the judgment operation of the judgment unit 9 is performed based on the signal. Start.

Thus, the output (position detection signal) of each determiner is distributed to each of the arm driving circuits 4 and 5 by the distribution circuit 8, and this driving circuit drives the output switching element 6, and the phase arm element and the rotor Are turned on and off in order so that the respective magnetic pole positions coincide.

FIG. 2 shows the operation timing, and the above operation makes it possible to control the speed of the three-phase brushless motor in accordance with the speed command 22.

Next, a countermeasure against noise generated by the output switching element 6 when the circuit enclosed by the dashed line shown in FIG. 1 is made monolithic will be described.

First, noise occurs in the Hall element output signal in synchronization with the chopping of the output switching element 6.

This noise is generated by the differential amplifier 10 with a filter.
The output switching element 6 turns on and off the DC voltage 141 V (= 100 × １００2), and the output of one Hall element is several hundred mV.
The effect on the noise is very large, and the noise removal by the amplifier must be incomplete.

In order to increase the filtering effect of the amplifier, it is sufficient to take measures such as increasing the capacitance of the capacitor. However, since the capacitance inside the chip is proportional to its occupied area, the chip area is increased, resulting in an inefficient operation. is there. Even if this is possible, it is not practical because the filtering effect is so great that a delay occurs, and the displacement between the position detection signal and the rotor magnetic pole of the motor is reduced, thereby reducing the efficiency of the motor.

For this reason, digital processing is performed using the decision unit 9 as in the present embodiment, and noise immunity is improved by taking double noise countermeasures.

FIG. 3 shows a timing chart of the operation of the determiner in this embodiment.

In FIG. 3, the timing of the judgment operation of each judgment unit 9 and the switching operation of the output switching element is performed through the distribution circuit 8 and the IGBT drive circuit 4 or 5, so that the judgment operation is performed before switching noise occurs. Starting, and thus the noise does not affect the position detection signal, and the noise immunity is improved.

Next, another embodiment of the present invention will be described with reference to FIG.

In FIG. 4, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

The difference from FIG. 1 is that the edge synthesizer 26 has a function of outputting a pulse signal for a certain period of time with respect to the edge-combined signal of the pulse width modulation signal and the clock signal.
Is to take the AND condition with the output of the differential amplifier 10.

As a result, noise generated by switching of the output switching element 6 is removed by the edge synthesizer 26.
This has the effect of improving the noise resistance of the output signal of the differential amplifier 10, which is a magnetic pole position detection signal, masked by the output signal of FIG.

Next, still another embodiment of the present invention will be described with reference to FIG.

In FIG. 5, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

The difference from FIG. 1 is that a one-shot pulse generator 28 which provides a hysteresis in the differential amplifier 10, eliminates the decision unit 9, and outputs a pulse for a certain period in synchronization with the output of the edge synthesizer. And making the differential amplifier insensitive by increasing the hysteresis width of the amplifier 27 with hysteresis by the one-shot pulse generation period.

FIG. 6 shows a circuit configuration of the amplifier 27 with hysteresis.

In FIG. 6, assuming that the pulse input signal is low, the output signal of the Hall element is differentially compared by the comparator 29 and the output of the comparator 29 is
Feedback is fed back to the plus input side of the comparator 29 via 0 and a resistor connected in series with the 0.

Thus, a hysteresis characteristic is provided by the ratio between the input resistance of the Hall element and the feedback resistance.

The hysteresis width at this time should be smaller than the Hall element input signal, and the hysteresis characteristic must not prevent the comparator output from turning on and off.

That is, the input resistance and the feedback resistance are set so that the comparator 29 outputs high or low according to the Hall element input signal.

Next, when a one-shot pulse is generated in synchronization with the output of the edge synthesizer, that is, when the pulse input goes high, the analog switch 30 is turned off and the analog switch 31 is turned on.

At this time, the resistance connected in series to the analog switch 31 is set so as to be larger than the above-mentioned hysteresis width, so that the comparator 29 does not operate even by disturbance such as a Hall element output signal and noise. .

Thus, the noise generated by the switching of the output switching element 6 is reduced by the edge synthesizer 26.
The noise resistance of the output signal of the differential amplifier 27 which is a magnetic pole position detection signal masked by the output signal of the differential amplifier 27 can be improved.

[0045]

According to the present invention, the effect of noise generated by main circuit switching on a weak Hall element output signal can be prevented, so that an external circuit for converting a Hall element signal into a logic signal can be eliminated. effective.

[Brief description of the drawings]

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

FIG. 2 is a magnetic pole position detection signal and an on / off timing chart of an output switching element.

FIG. 3 is a timing chart of the operation of a determiner according to an embodiment of the present invention.

FIG. 4 is a configuration diagram of a three-phase brushless motor drive circuit according to another embodiment of the present invention.

FIG. 5 is a configuration diagram of a three-phase brushless motor drive circuit according to still another embodiment of the present invention.

FIG. 6 is a configuration diagram of a differential amplifier with hysteresis.

[Description of Signs] 1 ... Commercial 100V AC power supply, 2 ... DC converter, 3 ... Smoothing capacitor, 4 ... Upper arm IGBT drive circuit, 5 ... Lower arm IGBT drive circuit, 6 ... IGBT, 7 ... Diode, 8 ... Phase Signal distribution circuit, 9 ... determiner, 10 ... differential amplifier with filter, 11 ... comparator, 12 ... automatic speed controller, 13 ... triangular wave and clock generator, 14 ... internal power supply, 15 ... phase comparator, 16, 17 ... impedance,
Reference numeral 18: detector, 19: three-phase brushless motor, 20: Hall element, 21: speed detection coil, 22: speed command oscillator, 23: edge synthesizer, 24: triangular wave signal, 25: A
ND circuit, 26: Edge synthesizer with constant pulse output, 2
7 ... Differential amplifier with hysteresis, 28 ... One-shot pulse generator, 29 ... Comparator, 30, 31 ... Analog switch.

──────────────────────────────────────────────────の Continued on the front page (72) Inventor Hiromitsu Nakano 1006 Kadoma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. (72) Inventor Masahiro Yasohara 1006 Odakadoma Kadoma, Osaka Pref. Matsushita Electric Industrial (56) References JP-A-61-247290 (JP, A) JP-A-4-67759 (JP, A) JP-A-3-270677 (JP, A) JP-A-3-34692 (JP, A) U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H02P 6/12

Claims (2)

(57) [Claims] An AC power supply is rectified and smoothed by a capacitor connected in parallel, and a DC power supply is connected in parallel with the capacitor by connecting a full-bridge arm of a switching element and a diode in anti-parallel connection. A three-phase main circuit; a speed control circuit that generates a pulse width modulation signal that adjusts an on-duty ratio of at least one switching element of the paired arms of the main circuit based on a speed deviation of the motor; and a magnetic pole of the three-phase brushless motor. In accordance with a position detection signal of a position detection element output for detecting a position, a signal for sequentially turning on and off the switching elements of each phase is generated,
A three-phase brushless motor drive circuit, comprising: a three-phase main circuit, a speed control circuit, and a phase distribution circuit. The circuit has a monolithic configuration , and a position detection signal output from the position detection element is supplied to a differential amplifier.
Through a first noise elimination circuit having a capacitor and a capacitor
Main circuit switching noise superimposed on the position detection signal
And the logical sum of the position detection signal from which the switching noise is removed, the internal clock, and the edge of the pulse width modulation signal.
And a circuit for determining whether the position detection signal is high or low.
Three-phase brushless motor drive circuit comprising the second switching noise elimination circuit. 2. The method of claim 1, comprising a second switching noise elimination circuit for masking the pulse signal having a constant period output signal synchronized with the pulse width modulation signal of the first switching noise elimination circuit
Driving circuit of a three-phase brushless motor, characterized in that there.