JPH0368635B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a protection circuit for a servo motor control device that allows reversible control using a final stage output element consisting of a transistor or a thyristor.

Conventionally, four or two DC servo motors, etc.
In a servo motor control device that enables reversible control using multiple power transistors, an operational amplifier or gate IC is used to control the motor DC power to prevent both forward and reverse power transistors from turning on at the same time and causing short circuits and destruction. An electronic circuit interlocks control signals to the forward and reverse power transistors.

However, operational amplifier or gate IC
There were various problems with interlocks at the electronic circuit level and logic level.

For example, when the power is turned on or disconnected, transient rises and falls of the electronic circuit DC power supply cause the electronic circuit to malfunction, generating both forward and reverse control signals, shorting the motor DC power supply and causing expensive power transistors and This also caused damage to the transistors in the previous stage.

For this reason, the base of the transistor in the previous stage that controls the power transistor is usually connected to ground, etc. using a relay contact for microcurrent control, etc., so that no signal is output to the power transistor.
There were cases where the forward and reverse outputs occurred at the same time due to poor contact in relay contacts or defective parts. In addition, photocouplers are used to isolate electronic circuits such as operational amplifiers from the power transistor drive circuit connected to the motor DC power supply circuit, but due to variations in the photocoupler components, there is a delay in the transmission of the photocoupler's output waveform. In some cases, the forward and reverse signals were output at the same time. Furthermore, electronic circuits may malfunction due to external noise, causing both forward and reverse signals to be output at the same time.To prevent this, it is conceivable to connect a noise absorbing capacitor to the base circuit of the power transistor, but generally PWM ( pulse wide
Since the modulation control method controls at several KHz, this method could not be used.

As described above, since the interlock generally used in the past is not an interlock in the power transistor of the final output stage, reliable operation cannot be expected. In the past, interlocks at the final output stage existed, but they were very expensive and were only applied to a small number of devices.

In view of the above points, it is an object of the present invention to provide a protection circuit for a motor control device that operates reliably and is inexpensive to manufacture.

That is, the present invention provides forward rotation control signal detection and reverse rotation control signals that are controlled by forward rotation and reverse rotation control signals that are respectively input to the forward rotation and reverse rotation final stage output elements that supply drive current to the motor. A photocoupler for detection is provided, and the turn-off time value of this photocoupler is set to a value larger than the storage time value when the final stage output element is a transistor, or larger than the turn-off time value when the final stage output element is a thyristor. and a means for blocking the supply of the reverse rotation control signal to the reverse rotation final stage output element by the output of the forward rotation control signal detection photocoupler; means for cutting off the supply of the forward rotation control signal to the element, and when the forward rotation and reverse rotation control signals are generated at the same time, both the forward rotation and reverse rotation control signals are cut off. , the control signal input to the final stage output element is detected and the opposing control signal is cut off, during the storage time period if the final stage output element is a transistor, and during the storage time period if the final stage output element is a thyristor. Opposite control signals are cut off even during the turn-off time, and both forward and reverse control signals are cut off when they occur at the same time, so operation is extremely reliable and the circuit configuration is simple. It can be manufactured cheaply.

An embodiment of the present invention will be described below based on the drawings. FIG. 1 shows a power transistor circuit at the final output stage of a motor control device, where 1 is a transformer, 2 is a rectifier, C ₁ is a capacitor, R ₁ is a discharge resistor, and 3 is a DC motor. The voltage stepped down by the transformer 1 is rectified by a rectifier 2, smoothed by a capacitor _C1 , and becomes a DC power source for a DC motor 3. _Q1
- Q ₄ are power transistors, and for example, when the power transistors Q ₁ and Q ₂ are turned on, the DC motor 3 rotates in the forward direction, and when the power transistors Q ₃ and Q ₄ are turned on, the DC motor 3 rotates in the reverse direction. 4a to 4d are base drive circuits of the power transistors _Q1 to _Q4 , _L1 is a reactor, 5 is a thermal relay, 6 is a DC transformer using a Hall element for current detection, and _D1 to _D4 are free circuits. It is a wheeling diode.

The base drive circuits 4a to 4d will be explained with reference to FIG. The voltage of the transformer 7 is rectified by a rectifier 8 and smoothed by a capacitor _C2 . When current flows through the input side diode (not shown) of the photocoupler and the output of the output side transistor _Q5 goes high, transistor _Q6 turns on, which turns off transistor _Q7 and turns off transistor _Q8 . When turned on, the base current is supplied to the corresponding power transistor among the power transistors Q ₁ to _{Q 4} via the resistor R ₂ and the terminal 9,
This power transistor turns on. diode
_D5 is for preventing transistor _Q8 from turning on when transistor _Q6 is off. Resistor R ₃ , diode D ₆ , capacitor C ₃ , and diodes D ₇ to _{D 10} are connected to V _F (0.7V) × between the base and emitter of the power transistor when transistor Q ₆ is off and transistor Q ₇ is on. 4=
This is to provide a reverse bias of about 2.8V.

The part surrounded by the broken line A is a feature of the present invention, and this part did not exist in conventional base drive circuits. When transistor _Q8 turns on, the voltage developed across resistor _R2 causes resistor _{R4 to}
Current flows through the input side diode _D11 of the photocoupler. _D13 is a reverse voltage protection diode for the input side diode _D11 . Input side diode D ₁₁
The output side of is connected to the base circuit of the interlocking power transistor. That is, the input side diode _D11 of the base drive circuit 4a and the output side transistor _Q11 of the base drive circuit 4d.
Then, the interlock of the base drive circuit 4a becomes
Input side diode D ₁₁ of base drive circuit 4b
and the output side transistor of the base drive circuit 4c
With _Q11 , the interlock of the base drive circuit 4b is connected to the input side diode of the base drive circuit 4c.
The interlock of the base drive circuit 4c is established between D ₁₁ and the output side transistor Q ₁₁ of the base drive circuit 4b, and the base drive circuit 4d is established between the input side diode D ₁₁ of the base drive circuit 4d and the output side transistor Q ₁₁ of the base drive circuit 4a. The interlocks are configured respectively. Therefore, if the output level of the output side transistor Q ₁₁ of the photocoupler becomes high level, the output level of the transistor Q ₁₂
is turned on, cutting off the base signal of the power transistor for reverse rotation in the case of forward rotation, and cutting off the base signal of the power transistor for normal rotation in the case of reverse rotation, thereby making it possible to interlock. 10 is a terminal connected to the emitter of the power transistor. _D14 is a reverse voltage protection diode for the output side transistor _Q11 . Power transistor Q ₁ ~
The interlock during the storage time period of _Q4 will be explained based on the signal waveform diagram of the main part in FIG. The drive input signal of transistor _Q5 falls, the output signal of transistor _Q5 falls,
Even if the input signal of the interlock photocoupler diode D ₁₁ falls, transistors Q ₁ and Q ₂
A collector current Ic flows during the storage time period. However, at this time, the output signal of the photocoupler transistor _Q11 falls with a delay longer than the storage time of the power transistors _Q1 to _Q4 . Therefore, even if the erroneous input signal of transistor _Q5 on the reverse side rises, the interlock signal from transistor _Q11 is still output, so the collector current Ic of power transistors _Q3 and _Q4 is equal to that of power transistor _Q1. , rises after the collector current Ic of _Q2 is cut off. Therefore, the power transistor
A power supply short circuit of Q ₁ to _{Q 4} does not occur, and the motor circuit can be reliably protected during the storage time period of the power transistors Q ₁ to _{Q 4} .

Referring to FIG. 4, FIG. 4 is an explanatory diagram of the turn-off time of the photocoupler, and shows the relationship between the photocoupler output side transistor voltage V _CE and the input side diode current _IF of the photocoupler. Further, the turn-off time of the photocoupler is the output waveform transmission delay time of the photocoupler.
The value of the photocoupler turn-off time t _OFF in FIG. 4 is selected to be larger than the storage time value when the final stage output element is a transistor, and larger than the turn-off time value when it is a thyristor. In this way, the input side diode _D11 and the output side transistor
A photocoupler consisting of Q ₁₁ and a transistor Q ₁₂
using power transistors Q ₁ , Q ₄ and Q ₂ ,
The control signals input to the base of Q ₃ are mutually interlocked, and the turn-off time value of the photocoupler is determined from the storage time value when the final stage output element is a transistor, and from the storage time value when the final stage output element is a thyristor. is selected to be larger than the turn-off time value, and when forward and reverse control signals are generated at the same time, they are both cut off, so that forward rotation control signals caused by various factors as described in the conventional example Destruction of the power transistors Q ₁ to _{Q 4} and the like due to the simultaneous occurrence of the reverse control signal and the reverse control signal can be reliably prevented during the storage time period and the turn-off time period, and the circuit configuration can be simple and manufactured at low cost. Furthermore, when controlling using the PWM method, there is no need to use an expensive high-speed photocoupler with small output waveform transmission delay as in the past. In other words, as explained in Fig. 3, the power transistor is
It is protected during the storage time period of Q ₁ to Q ₄ ,
This is because there is no problem even if the output waveform transmission delay of the photocoupler is large. Furthermore, servo motors used in industrial robots and the like frequently rotate in forward and reverse directions, but even in such cases, an interlock is applied during the storage time of power transistors _Q1 to _Q4 . During the storage time period, the power transistors Q ₁ to _{Q 4} on the opposite side do not conduct, and the power transistors Q ₁ to
This prevents the power supply of Q ₄ from being shunted between the upper and lower power transistors Q ₁ to _{Q 4} , and it reliably prevents damage to the power transistors Q ₁ to _{Q 4} , which improves the operating rate and contributes to improved productivity. It's a big deal.

In the above embodiment, an example has been described in which the collector of the photocoupler output side transistor _Q11 is connected to the power supply line, but this collector may be connected to the terminal 9. Alternatively, a PNP transistor may be used as the transistor _Q12 , and its base may be connected to the collector of the output side transistor _Q11 . Further, as the transistor Q ₁₂ , if the power transistors Q ₁ to _{Q 4} have a large capacity, a Darlington transistor with small waveform transmission delay may be used.

Further, in the above embodiment, an example was explained in which four power transistors Q ₁ to _{Q 4} were used as the final stage output element, but the present invention can also be applied to a case where there are two power transistors, and also when the final stage output element It can be applied even if it is a thyristor.

Further, in the above embodiment, an example in which the DC motor 3 is controlled has been described, but the present invention can also be applied to a motor control device that controls an AC motor, a three-phase motor, or the like.

As explained above, according to the protection circuit of the motor control device according to the present invention, since the interlock is provided at the final stage, it is possible to reliably prevent destruction of the final stage output element, etc., and the circuit configuration is It can be manufactured easily and inexpensively. Furthermore, even during the storage time period of the final stage output element, such as a power transistor, the output waveform transmission delay time of the photocoupler is interlocked so that the power transistor on the opposite side does not become conductive immediately even if the drive output signal falls. Since the interlock is guaranteed even during the storage time period, the interlock can be reliably realized at an extremely low cost and is useful in high-power motor control circuits and the like.

Furthermore, even if the storage time and turn-off time of the final stage output control element fluctuate due to ambient temperature fluctuations, for example, if they become larger, the turn-off time of the photocoupler will change accordingly and become larger, so it must be corrected. I can do it.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, in which Fig. 1 is a circuit diagram of a power transistor circuit in the final output stage of a motor control device, Fig. 2 is a circuit diagram of a base drive circuit, and Fig. 3 is a signal waveform of the main part of the circuit. 4 are explanatory diagrams of the photocoupler turn-off time. 3...DC motor (motor), _Q1 , _Q2 ...Power transistor (final stage output element for forward rotation), _Q3 ,
Q ₄ ... Power transistor (final stage output element for reversal), D ₁₁ ... Input side diode of photocoupler for control signal detection, Q ₁₁ ... Output side transistor of photocoupler for control signal detection, Q ₁₂ ... Transistor.

Claims (1)

[Claims] 1 Photocouplers for detecting forward rotation control signals and for detecting reverse rotation control signals, which are controlled by the forward rotation and reverse rotation control signals that are respectively input to the forward rotation and reverse rotation final stage output elements that supply drive current to the motor. The turn-off time value of the photocoupler is determined from the storage time value when the final stage output element is a transistor, and from the turn-off time value when the final stage output element is a thyristor.
means for selecting a large value and cutting off the supply of the reverse rotation control signal to the reverse rotation final stage output element by the output of the forward rotation control signal detection photocoupler;
means for cutting off the supply of the forward rotation control signal to the forward rotation final stage output element by the output of the reverse rotation control signal detection photocoupler; A motor control device that cuts off both diversion and reversal control signals.