JPS63283423A - Runaway preventive circuit for motor driver - Google Patents

Abstract

PURPOSE:To prevent a motor from running away by detecting the defect of the speed feedback signal of a speed detector arbitrarily mounted except when the F/V converter output of a phase detector is utilized as the speed feedback signal. CONSTITUTION:The speed feedback signal of a DC motor 2 detected by an F/V converter 6, a current feedback signal from a current detector 8, and the signal of a pulse width modulation circuit 10 are led to a runaway detection circuit 11 to discriminate the presence or absence of a malfunction. If the malfunction of the case when a speed feedback signal is defective due to the disconnection of a speed detector 14 occurs, the output signal of the modulation circuit 10 is interrupted by a protective circuit 12, and a base drive signal is turned OFF to stop the operation of a power amplifier 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a circuit for preventing runaway of an electric motor due to loss of a position or velocity feedback signal in an electric motor drive device.

[Prior art and its problems]

The present invention is based on the previously proposed runaway prevention circuit (Japanese Patent Application Laid-Open No. 61-94
573).

In the above-mentioned prior art, since <R1 drop compensation is based on the armature resistance of the motor using a fixed bias method, there is a drawback that the runaway detection sensitivity must be lowered in the case of a motor with a large armature resistance. (Decrease in runaway detection sensitivity means that the motor rotation speed increases from the time the motor runs out of control until the protection circuit operates.) In addition, the F/V signal of the position feedback pulse is used as the speed feedback signal. If the position sensor is defective, the speed feedback signal will be lost at the same time, so the circuit functions as a runaway prevention circuit. In this case, there was a problem in that the defect in the DC tachogenerator could not be detected.

Therefore, the present invention provides a method for detecting runaway without reducing runaway detection sensitivity even in motors where the armature resistance of the motor armature winding is large.
And as a speed feedback signal, F of the position detector
The present invention attempts to provide a runaway prevention circuit that detects a loss in the speed feedback signal of an arbitrarily attached speed detector and prevents the motor from running out of control, except when the /V converter output is used.

(Means for Solving the Problems) The present invention has been made to solve the above problems. a pulse width modulation circuit that converts the PWM signal into a DC voltage via a low-pass filter, and a comparator that compares the voltage obtained by converting the PWM signal into a DC voltage with a reference voltage controlled by the magnitude of the current feedback signal. It detects "motor induced voltage generation" from the output signal of the comparator, and converts the feedback pulse from the position detector or speed detector of the motor rotating shaft into a voltage using an f/■ (frequency/voltage) converter. The converted signal is passed through a window comparator to detect the "motor rotating" signal, and if the "motor rotating" signal is off even though the "motor induced voltage generation" signal is on, it is determined to be abnormal. Accordingly, the protection circuit is activated and the supply of the PWM signal to the base drive circuit is cut off.

Embodiments of the present invention will be described below based on the drawings.

〔Example〕

1 and 2 are block diagrams each showing an example of the configuration of a DC motor control device embodying the present invention. The embodiment shown in FIG. (2) In the case where the speed feedback signal is obtained by the converter 6, the embodiment shown in FIG. 2 is an example in which the speed feedback signal is obtained by the speed detector 14 provided separately.

In the embodiment shown in FIG.
The converter 5 forms a position control loop together with the position detector 3, and outputs the deviation obtained by subtracting the feedback pulse of the position detector 3 from the position command pulse as a speed command value.

The feedback pulse is detected as the rotational speed of the DC motor 2 via the F/V converter 6, and provides a speed feedback signal for the speed command.

The amount of deviation between the speed command value and the speed feedback signal is outputted as a current command value via the speed amplifier 7.

This current command value and the resistance IR or 2R of power amplifier 1
The amount of deviation from the armature current of the DC motor 2 detected by the current detection circuit 8 is passed through the current amplifier 9, pulse width modulated by the pulse width modulation circuit 10, and then input to the base drive circuit 13. The power transistors ITr to 4Tr of the power amplifier 1 are controlled on and off to drive the DC electric motor m2.

On the other hand, the speed feedback signal of the DC motor 2 detected by the F/V converter 6, the current feedback signal from the current detection circuit 8, and the signal of the pulse width modulation circuit 10 are as follows.
The runaway detection circuitry 1 determines whether there is an abnormality.

If there is an abnormality, the protection circuit 12 cuts off the output signal of the pulse width modulation circuit 10, turns off the base drive signal, and stops the operation of the power amplifier 1.

In the embodiment shown in FIG. 2, in the first embodiment,
A speed feedback signal is transmitted to a speed detector 14 provided separately.
It performs similar operations except that it is guided by . The runaway detection circuit 11 also receives a signal from the speed detector 14 in addition to the F/ViJA signal of the feedback pulse from the position detector 3, the current feedback signal from the current detection circuit 8, and the signal from the pulse width modulation circuit 10. is guided. In this case, the signal from the F/V converter 6 is used for the position detector, and the signal from the speed detector 14 is used to determine whether the speed detector 14 is abnormal.

Next, the operation of the runaway detection circuit 11 according to the present invention will be explained.

FIG. 3 shows details of the runaway detection circuit 11 shown in FIG. 2, and FIG. 4 shows the output V of the current amplifier 9 in FIG. 3, the output of the pulse width modulation circuit 10, and the comparator 31C.
, 41C.

The pulse width modulated signals of the comparators 11C and 2IC are input to the base drive circuit 13 through analogues 6ic and 7ic, respectively. The output of the AND gate 6ic corresponds to a signal that applies rotational force in the forward direction to the DC motor 2, and the output of the AND gate 7ic corresponds to a signal that applies rotational force in the reverse direction.

These signals are smoothed by a low-pass filter constituted by a resistor 3R and a capacitor IC, and then sent to a comparator 31.
The signal is smoothed by a filter including a negative (-) input of C, a resistor 4R, and a capacitor 2C, and is applied to a negative (-) input of a comparator 41C. The DC voltage smoothed by each filter simulates the terminal voltage of the DC motor 2, and the comparator 31C
detects the terminal voltage of the positive polarity DC motor 2, and the comparator 4
1C detects the terminal voltage of the negative polarity DC motor.

On the other hand, a comparison reference voltage obtained by dividing a positive voltage source by resistors 6R and 7R is given to the positive (+) input terminals of comparators 3IC and 4IC, and this reference voltage is applied to the current feedback signal (10 ), and when the current is large, the reference voltage is large.

Become. That is, Lb is connected to the resistor 6R via the positive absolute value circuit 15 and the gain adjuster 16, and when irb is 0, the reference voltage EFa is as follows.

Here, the proportionality constant is adjusted by the gain adjuster 16 and is proportional to the magnitude of the armature resistance of the DC motor 2. In addition, K l i, l provides R1 drop compensation for the DC motor 2, and by compensating the comparison reference voltage of the comparator 3C, 41C for the R1 drop, the induced voltage (not the terminal voltage) of the motor can be detected. can do. That is, when the voltage corresponding to the induced voltage of the motor exceeds , it is determined that the motor has rotated, and the output of the inverter 10ic becomes H. (“Motor induced voltage generation”
signal).

Since the generation of induced voltage in the motor means that the rotor has rotated, at this time, the speed signal of the DC motor 2, F/
The V converter signal and the speed feedback signal of the speed detector 14 should be generated with magnitudes proportional to the rotational speed.

Therefore, this detection can be easily realized using window comparators 17 and 18. FIG. 5 shows this relationship.

Now, if the motor is rotating and the position detector 3 is normal, the output of the window comparator 18 becomes H. And if the speed detector 14 is normal, the window comparator 18
The output becomes H. At this time, the output of the Nant gate 9ic becomes L, and the output of the AND gate 8ic remains unchanged.

The above-mentioned relationship is illustrated in a time chart as shown in FIG. 6 in an easy-to-understand manner.

(A) Normal operation First, when the motor starts rotating, the output b (“motor rotating” signal) of the window comparator 17 becomes H.

Next, the output C (second "motor rotating" signal) of the window comparator 18 becomes H. (There is no particular restriction on the output order of signals S and C. → Whichever signal may be output earlier is fine.) Subsequently, the output a (“motor induced voltage generation” signal) of the inverter 10ic becomes H.

During normal operation, the time point 1+ when the signals S and C become 11.

t2 must always be earlier than the time t3 when the signal a becomes H. The point at which this t3 should occur is the resistor 6R.
, 7R. At this time, the output e of the anime game 1-8ic is always on.

(B) Operation under abnormal conditions...Breakdown of the position detector 3If the feedback pulse is lost due to a break in the position detector 3, the output of the F/V converter 6 remains O■,
The output of the signal also remains at L. At this time, the output of the Nant gate 9ic is H, and when the signal a changes to L-+H, the signal e changes to L-+H. Output f of protection circuit 12
latches this change and becomes L, and the outputs of AND gates 6ic and 7ic of the pulse width modulation circuit 10 are set to L,
The output to the base drive circuit 13 is cut off.

(C) Operation at abnormal times...Disconnection of the speed detector 14 When the speed feedback signal is lost due to a disconnection of the speed detector 14, etc., the base drive circuit 13 performs the same operation as in (B) above. Output to is cut off. (6th
See the time chart in Figure (C)). ) [Modifications and Applications of the Invention] (1) In the above embodiment, the speed detector 31 position detector 1
This article describes the runaway prevention circuit when the feedback signal is lost in No. 4. However, a runaway detection circuit when the signal polarity is reversed due to a connection error is not shown. These will be omitted since they are combined with the circuit of the prior art described above.

(2) Furthermore, when applying FIG. 3 to the runaway detection circuit corresponding to FIG. 1, the configuration may be such that the output of the window comparator 18 is always H.

(Alternatively, the F/V signal may also be input to the tachogenerator signal (TG) part.) (3) Although this application example shows the case of a DC motor drive device, the circuit configuration of the pulse width modulation circuit 10 is described above. If the circuit is modified in the same way as the prior art circuit, it can also be applied to an AC motor drive device.

[Effects of the Invention] In the conventional example, if the motor has a large armature resistance or a large starting current, it is necessary to considerably reduce the detection sensitivity of the runaway state by R11071.

However, according to the present invention, by adding an RI drop compensation circuit, the runaway detection sensitivity can be greatly improved regardless of the motor model. Furthermore, as a speed feedback signal, it is possible to detect a loss in not only the F/V converter type but also any speed detector signal provided separately.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a block diagram of a different embodiment of the present invention, FIG. 3 is a block diagram showing details of the runaway detection circuit in FIG. 3, and FIG. 4 is a block diagram of a different embodiment of the present invention. A diagram showing the relationship between the output of the current amplifier in Figure 3, the output of the pulse width modulation circuit, and the input signal to the negative input terminal of the comparator, and Figure 5 shows the relationship between the motor rotation speed, F/V converter or tachogenerator output voltage, and the window・A diagram showing the relationship between comparator outputs, FIG. 6 is a time chart of signals of each part of the runaway detection circuit shown in FIG. 3 during normal and abnormal times. 1... Power amplifier 2... DC motor 3... Position detector 4... Deviation counter 5... D/A converter 6... F/V converter 7... Speed amplifier 8 ...Current detection circuit 9...Current amplifier 10...Pulse width modulation circuit 11...Runaway detection circuit 12...Protection circuit 13...Base drive circuit ITr~4Tr...Power transistor ID~ 4D・
...Diode ■R~2R...Current detection resistor 14...Speed detector Fig. 1 1...Power amplifier 1o...Pulse width modulation circuit 2...DC motor 11...Runaway detection path 3
...Position detector 12...4A protection circuit 4...Deviation counter 13...Base drive circuit 5...
D/A fma lTr~4)・Power transistor 6・・F/V father exchanger ID 4D・・
Diode 7...Exit amplifier +R, 2R...
Current detection resistor 8...Current detection path 9...Current amplifier 2nd Figure 1...Buff amplifier 10...Pulse width modulation circuit 2...DC motor 11...Runaway detection path 3
...Position detector 12..Protection circuit 40. Kago Kaunk 13...Pace Dry Pro Trace 5...D/
A converter 14...Speed detector 6...F/V driver U 7...Speed amplifier 8...Flow test Miguchi mark 9...Flow amplifier Figure 4 Figure 5 Figure 6 Figure (A) Normal movement of time

Claims (3)

[Claims] (1) A current amplifier that amplifies the amount of deviation between the current command and the current feedback signal, a pulse width modulation circuit that converts the output signal into a PWM (pulse width modulation) signal, and the PWM (pulse width modulation) signal.
It is equipped with a comparator that compares the voltage obtained by converting the M signal into a DC voltage through a low-pass filter with a reference voltage controlled by the magnitude of the current feedback signal, and calculates the "motor induced voltage" from the output signal of the comparator. At the same time, the feedback pulse from the position detector of the motor rotating shaft is converted into a voltage by an f/V (frequency/voltage) converter, and the signal is sent through a window comparator to detect the "motor rotating" signal. If the "motor rotating" signal is off even though the "motor induced voltage generation" signal is on, it is determined that there is an abnormality, the protection circuit is activated, and the PWM signal is not supplied to the base drive circuit. A runaway prevention circuit for an electric motor drive device, characterized in that the circuit is configured to be cut off. (2) a current amplifier that amplifies the amount of deviation between the current command and the current feedback signal; a pulse width modulation circuit that converts the output signal into a PWM (pulse width modulation) signal;
It is equipped with a comparator that compares the voltage obtained by converting the M signal into a DC voltage through a low-pass filter with a reference voltage controlled by the magnitude of the current feedback signal, and calculates the "motor induced voltage" from the output signal of the comparator. At the same time, a signal obtained by converting the feedback pulse from the position detector of the motor rotating shaft into a voltage by an f/V (frequency/voltage) converter is sent to the first
A second "motor rotating" signal is detected through the speed feedback signal from the speed detector via a window comparator, and the "motor induced voltage generation" signal is turned on. However, if either or both of the first and second "motor rotating" signals are off, it is determined that there is an abnormality, the protection circuit is activated, and the supply of the PWM signal to the base drive circuit is cut off. A runaway prevention circuit for an electric motor drive device, characterized in that the circuit is configured to do so. (3) a current amplifier that amplifies the amount of deviation between the current command and the current feedback signal; a pulse width modulation circuit that converts the output signal into a PWM (pulse width modulation) signal;
It is equipped with a comparator that compares the voltage obtained by converting the M signal into a DC voltage through a low-pass filter with a reference voltage controlled by the magnitude of the current feedback signal, and calculates the "motor induced voltage" from the output signal of the comparator. At the same time, a signal obtained by converting a feedback pulse from a speed detector of the motor rotating shaft into a voltage by an f/V (frequency/voltage) converter is used to detect "motor rotation" through a window comparator, If the "motor rotating" signal is off even though the "motor induced voltage generation" signal is on, it is determined that there is an abnormality, the protection circuit is activated, and the supply of PWM signals to the base drive circuit is cut off. A runaway prevention circuit for an electric motor drive device, characterized in that the circuit is configured to do so.