JPH07147783A - Abnormality detector for device where pulse width modulation is used - Google Patents

Abstract

PURPOSE:To monitor triangular waves so as to detect abnormality by inputting the output of wide pulses into an OR gate with first and second comparators which compare the signal from a triangular wave generator with positive reference voltage and negative reference voltage, respectively, and inverting the output of the OR gate with a NOT circuit, and latching the signal with a flip flop. CONSTITUTION:Positive reference voltage is inputted into the inversion input terminal of a first comparator 14, and a triangular wave signal into the noninversion input terminal. Moreover, negative reference voltage is inputted into the noninversion input terminal of a second comparator 15, and a triangular wave signal into the inversion input terminal. Hereby, the first and second comparators 14 and 15 output pulse signals constant in width and frequency, respectively And, first and second timers outputs the wide pulses of the signals, and an OR gate outputs a high signal. A NOT circuit inverts the high signal into a low signal, and inputs the output into a flip flop 20, thus an abnormality signal can be monitored from the output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device using a triangular wave comparison pulse width modulation method, which detects abnormalities in a device using pulse width modulation for confirming whether or not the output of a triangular wave oscillating section is normally oscillating. Regarding the device.

[0002]

2. Description of the Related Art Conventionally, as a triangular wave comparison pulse width modulation method, for example, the method shown in FIG. 3 has been proposed. In FIG. 3, the digital output of the control unit 1 is converted into a current command signal by the D / A converter 2, and this current command signal is input to the current deviation amplification unit 3. Further, the output of the current deviation amplification unit 3 is input to the pulse width modulation conversion unit 4, and the triangular wave signal from the triangular wave oscillation unit 5 is also input. Further, the signal from the pulse width modulation conversion unit 4 is input to the inverter circuit unit 6. Is converted into a driving current and input to the motor 8. Further, the current input to the motor 8 is detected by the current detection unit 7, and the detected current signal is input to the current deviation amplification unit 3. The rotation of the motor 8 is detected by the encoder 9,
The detected speed feedback signal is the control unit 1
Be fed back to.

In this triangular wave comparison pulse width modulation method, the digital command signal from the control controller 1 is D /
When input to the A converter 2, the digital command signal is converted to an analog current command signal by the D / A converter 2 and input to the current deviation amplifier 3. Here, the current command signal from the current detector 7 is compared, and the difference current command signal is input to the pulse width modulation converter 4. The pulse width modulation conversion unit 4 is composed of a comparator 10 as shown in FIG. 4, and the difference current command signal Vin is input from the current deviation amplification unit 3 to the terminal 11 as shown in FIG. When the triangular wave signal Vcar is input from the triangular wave oscillator 5 to the terminal 12, the terminal 1
A pulse Vout having a pulse width modulated as shown in FIG. 5B is output from 3 and input to the inverter circuit unit 6. The inverter circuit unit 6 receives the input pulse Vou
It is converted into a driving current according to t, and this driving current is converted to the motor 8
When the input is input to the motor 8, the motor 8 rotates, so that the rotation speed of the motor 8 is detected by the encoder 9. The detected speed feedback signal is input to the control unit 1, and the speed feedback signal is compared with a preset speed signal. Then, the digital command signal is output so that the rotation of the motor 8 reaches the set speed.

[0004]

By the way, in this triangular wave comparison pulse width modulation method, the oscillation of the triangular wave oscillating section 5 is stopped and the triangular wave signal Vcar is generated as shown in FIG. 5 (c).
Has a constant output, the pulse Vout output from the pulse width modulation conversion unit 4 has no output at the crossing position of the current command signal Vin and the triangular wave signal Vcar, and there is a drawback that it cannot be controlled.

According to the present invention, the first and second comparators compare the triangular wave signal with the positive and negative reference voltages, respectively, and if the triangular wave signal is normal, pulses are generated from the first and second comparators. So this pulse is the first,
If the second timer converts them into pulses of width T, these pulses are passed through the OR gate and inverted by the knot circuit, the output from the knot circuit disappears, the detection signal is not output, and the triangular wave signal becomes abnormal. It is an object of the present invention to provide an abnormality detecting device for a device using pulse width modulation, in which a pulse signal is output from a knot circuit and a detection signal is output from a flip-flop in response to the pulse signal.

[0006]

In order to achieve the above object, the present invention is a device for changing the pulse width by modulating a current command signal from a control section with a triangular wave signal from a triangular wave oscillating section. In, the first and second comparators for comparing the signal from the triangular wave oscillating section with the positive reference voltage and the negative reference voltage and the outputs of the first and second comparators are respectively converted into wide pulses. First and second timers, OR gates that pass the outputs of the first and second timers, a NOT circuit that inverts the outputs of the OR gates, and a flip-flop that latches a signal when there is an output of the NOT circuit It consists of and.

A positive reference voltage is input to the inverting input terminal of the first comparator, a triangular wave signal is input to the non-inverting input terminal, and a negative reference voltage is input to the non-inverting input terminal of the second comparator. The triangular signal is input to the inverting input terminal. The outputs of the first and second comparators are pulse signals whose width and frequency are constant.

The first and second timers output a pulse having a time width T by using the pulses from the first and second comparators as a trigger. When the triangular wave oscillator is oscillating normally, a high signal is output from the OR gate and inverted by the knot circuit, a low signal is output from the knot circuit to the flip-flop, and the detection signal is output from the output terminal of the flip-flop. Is not output.

When the oscillation of the triangular wave oscillator is stopped, the first,
No pulse is output from the second comparator and no pulse is output from the first and second timers, the output of the OR gate becomes a low signal, and the high signal is output from the knot circuit. It is latched by a flip-flop, and a detection signal for notifying an abnormality of the triangular wave oscillator is output from the output terminal of the flip-flop.

When the system reset signal is input to the terminal of the flip-flop when the triangular wave oscillator is repaired,
The output of the detection signal is stopped, and the original state can be restored.

[0011]

According to the present invention, by setting the positive and negative reference voltages ± Vref which are slightly smaller than the maximum amplitude of the triangular wave signal by the first and second comparators, the triangular wave signal becomes ± Vr.
It is detected whether or not it is vibrating more than ef. When the triangular wave oscillating unit is oscillating normally, pulse signals having a constant width and a constant frequency are output from the first and second comparators. A pulse having a time width T is output from the first and second timers by using the pulse output from the first and second comparators as a trigger. Then, when the pulse signals from the first and second timers are passed through the OR gate, if the triangular wave oscillating unit is oscillating normally, a high signal is output from the OR gate and inverted by the knot circuit. Outputs a low signal to the flip-flop, thus
No detection signal is output from the flip-flop. Here, when the triangular wave oscillating section becomes abnormal, no pulse is output from the comparator, and therefore the output of the OR gate becomes a low signal and the knot circuit outputs a high signal. Therefore, this high signal is latched by the flip-flop. By
A detection signal indicating that the triangular wave oscillator is abnormal is output.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, in an abnormality detecting apparatus for an apparatus using pulse width modulation according to one embodiment of the present invention, as shown in FIG. The positive reference voltage + Vref is input to the terminal, the triangular wave signal is input to the non-inverting input terminal, the negative reference voltage −Vref is input to the non-inverting input terminal of the second comparator 15, and the triangular wave signal is input to the inverting input terminal. A signal is input. As a result, the outputs of the first and second comparators 14 and 15 are pulse signals having a constant width and a constant frequency, respectively, as shown in FIGS. 2 (b) and 2 (c). These first,
When the pulses from the second comparators 14 and 15 are input to the first and second timers 16 and 17, FIG.
As shown in (e), the first and second timers 16 and 17 output a pulse having a time width T using the pulses from the first and second comparators 14 and 15 as triggers. And the first,
When the pulse signals from the second timers 16 and 17 are passed through the OR gate 18, the OR gate 18 outputs a high signal as shown in FIG. 2 (f). Therefore, when the triangular wave oscillating unit is oscillating normally, a high signal is output from the OR gate 18, and the knot circuit 19 is output as shown in FIG. 2 (g).
A low signal is output from the knot circuit 19 to the flip-flop 20 by inverting the signal in FIG.
As shown in, the detection signal is not output from the output terminal 21 of the flip-flop 20.

Here, when the oscillation of the triangular wave oscillating section is stopped as shown in FIG. 2 (a), the first and second comparators 14 and 15 are operated as shown in FIGS. 2 (b) and 2 (c). Since no pulse is output and therefore no pulse is output from the first and second timers 16 and 17 as shown in FIGS. 2 (e) and 2 (f), the OR gate shown in FIG. 2 (f) is used. 1
The output of 8 is a low signal. Therefore, since a high signal is output from the knot circuit 19 as shown in FIG. 2 (g), by latching this high signal by the flip-flop 20, the flip-flop 20 as shown in FIG. 2 (h). A detection signal for notifying an abnormality of the triangular wave oscillator is output from the output terminal 21 of the.

If the system reset signal is input to the terminal 22 of the flip-flop 20 when the triangular wave oscillator is repaired, the output of the detection signal is stopped and the original state can be restored.

[0015]

Since the present invention is configured as described above, when the oscillation of the triangular wave oscillating unit is stopped or the triangular wave becomes abnormal, the first and second comparators cannot detect the top of the triangular wave. Therefore, the output of the first and second timers and the output of the OR gate also become a low signal, and the signal from the knot circuit which is an inverted signal thereof becomes a high signal, and by latching this signal by the flip-flop, the detection signal is reliably output. Therefore, there is an effect that an abnormality can be detected by constantly monitoring the oscillation of the triangular wave.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an abnormality detection device for an apparatus using pulse width modulation according to an embodiment of the present invention.

FIG. 2 is an output waveform diagram of each part of the circuit of the abnormality detection device for an apparatus using pulse width modulation according to an embodiment of the present invention.

FIG. 3 is a block diagram of an apparatus using pulse width modulation according to the present invention.

FIG. 4 is a specific circuit diagram of a pulse width modulation conversion unit of the present invention.

FIG. 5 shows a signal waveform input to the pulse width modulation converter of the present invention.

[Explanation of symbols]

 14. First comparator 15. Second comparator 16. First timer 17. Second timer 18. OR gate 19. Knot circuit 20. flip flop

Claims (7)

[Claims] 1. A device in which a pulse width is changed by modulating a current command signal from a control unit with a signal from a triangular wave oscillating unit, wherein the triangular wave signal from the triangular wave oscillating unit, a positive reference voltage, and a negative reference voltage are used. First and second comparators that compare the reference voltages of the first and second comparators, first and second timers that convert the outputs of the first and second comparators into wide pulses, respectively, and the first and second timers. Apparatus using pulse width modulation, comprising an OR gate for passing the output of a timer, a NOT circuit for inverting the output of the OR gate, and a flip-flop for latching a signal when the output of the NOT circuit is present. Abnormality detection device. 2. A positive reference voltage is input to the inverting input terminal of the first comparator, a triangular wave signal is input to the non-inverting input terminal, and a negative reference voltage is input to the non-inverting input terminal of the second comparator. The abnormality detection device for a device using pulse width modulation according to claim 1, wherein a triangular wave signal is input to the inverting input terminal. 3. The abnormality detecting device for an apparatus using pulse width modulation according to claim 1, wherein the outputs of the first and second comparators are pulse signals having a constant width and a constant frequency. 4. An apparatus using pulse width modulation according to claim 1, 2 or 3, wherein the first and second timers output a pulse of time width T triggered by the pulse from the first and second comparators. Abnormality detection device. 5. When the triangular wave oscillating section is normally oscillating, a high signal is output from the OR gate and inverted by the knot circuit, whereby a low signal is output from the knot circuit to the flip-flop, and The abnormality detection device for an apparatus using pulse width modulation according to claim 1, wherein no detection signal is output from the output terminal. 6. When the oscillation of the triangular wave oscillating unit is stopped, no pulse is output from the first and second comparators and no pulse is output from the first and second timers, so that the output of the OR gate becomes a low signal. The pulse width according to claim 1, wherein a high signal is output from the knot circuit, the high signal is latched by a flip-flop, and a detection signal for notifying an abnormality of the triangular wave oscillator is output from the output terminal of the flip-flop. A device abnormality detection device using modulation. 7. The pulse according to claim 1, wherein when the system reset signal is input to the terminal of the flip-flop when the triangular wave oscillator is repaired, the output of the detection signal is stopped and the pulse can be returned to the original state. Anomaly detection device for equipment using width modulation.