JPS6156802B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ON/OFF type servo circuit, and more particularly to a servo circuit to which a capacitor actuated control motor or an electric slider is connected as a load.

When a capacitor-activated control motor or electric slider switches instantaneously from forward rotation to reverse rotation, or from reverse rotation to forward rotation, the power to counteract the inertia of the motor or the charge of the phase advance capacitor, etc., is instantly consumed, and the relay There was a problem that excessive current flowed through the contacts, leading to rapid deterioration and welding.

The present invention has been made in view of the above points, and includes a pair of relays driven by current supplied from a common AC power source and a gate that can be turned on and off by supplying current to the gate. a first control rectifier consisting of an SCR that controls the current supplied from the AC power supply to each relay by switching the state;
When the second controlled rectifying element consisting of an SCR or RUT and the first controlled rectifying element are switched to the OFF state, a current is supplied to the gate of the second controlled rectifying element with a delay for a predetermined time, and during this time second to
a first current control circuit consisting of a first detection circuit and a first time constant circuit that turns the controlled rectifier into an OFF state and turns the second controlled rectifier into an ON state after the supply ends; Control rectifier is OFF
When the current is switched to the state, a current is delayed and supplied to the gate of the first controlled rectifying element for a predetermined time, the first controlled rectifying element is turned OFF during this time, and after the supply ends, the first controlled rectifying element is switched to the OFF state. The purpose of the relay is to prevent deterioration and welding of the relay contacts as a configuration that includes a second current control circuit consisting of a second detection circuit that turns the element into an ON state and a second time constant circuit. be.

Next, the present invention will be described with reference to illustrated embodiments.

FIG. 1 is a block diagram showing a flow rate regulating system in which a servo circuit according to the present invention is used.
In the figure, 1 is a flow rate sensor or a temperature sensor such as a reaction tank, and 2 is a PID operation circuit into which the detected value of the sensor 1 is input. 3 is a constant voltage circuit,
A potentiometer 4 is connected to the constant voltage circuit 3, and the voltage obtained by the potentiometer 4 and the output voltage of the PID operation circuit 2 are input to an operational amplifier 5. The output of this operational amplifier 5 is applied to a load motor 7 via a servo circuit 6 according to the present invention, and a rotor 7a of the motor 7 is connected to an actuator 8a of a flow control valve 8 and the potentiometer 4. There is.

As shown in FIG. 2, the servo circuit 6 includes a pair of relays M ₁ and M ₂ that are driven by current supplied from a common AC power source 9, and a gate that is turned on and off by supplying current to the gate. First and second control rectifier elements S ₁ and S ₂ that control the current supplied from the AC power supply 9 to each relay M ₁ and M ₂ by switching the OFF state
When the first controlled rectifying element _S1 is switched to the OFF state, a current is supplied to the gate of the second controlled rectifying element _S2 with a delay for a predetermined period of time, and during this period, the second controlled rectifying element S1 is switched to the OFF state. A first current control circuit 15 consisting of a first detection circuit and a first time constant circuit 11 that turns S ₂ into an OFF state and turns the second control rectifier S ₂ into an ON state after completion of supply; When the second controlled rectifying element _S2 is switched to the OFF state, a current is supplied to the gate of the first controlled rectifying element _S1 with a delay for a predetermined time, and during this period, the first controlled rectifying element
A second current control circuit 16 consisting of a second detection circuit and a second time constant circuit 12 turns S ₁ into an OFF state and turns the first control rectifier S ₁ into an ON state after the supply ends. It is configured. In detail, the input terminal 1 is connected to the output terminal of the operational amplifier 5.
3 is a diode that allows current to pass in the positive direction
The first is used SCR through D ₃ and resistor R ₃
is connected to the gate of the controlled rectifier _S1 , and
Diode D ₄ that passes current in the negative direction
and is connected via a resistor R ₄ to the gate of a second controlled rectifying element S ₂ in which PUT is used. Further, the first controlled rectifying element _S1 , the relay _M1 , and the AC power supply 9 are connected in series, and the anode of the first controlled rectifying element _S1 is connected to the first diode _D1.
and is connected to the gate of the second controlled rectifier S ₂ via the first current control circuit 15 . The first current control circuit 15 is constituted by a diode _D1 which constitutes a first detection circuit, and a series circuit of a capacitor _C1 and a resistor _R1 which constitutes a first time constant circuit 11. . On the other hand, the second controlled rectifying element S ₂
The relay M ₂ and the AC power supply 9 are connected in series, and the cathode of the second controlled rectifier S ₂ is connected to the first controlled rectifier S ₁ via the second current control circuit 16.
connected to the gate. The second current control circuit 16 includes a diode D ₂ forming a second detection circuit.
and a capacitor C ₂ forming the second time constant circuit 12.
and a resistor _R2 in series. Furthermore, the first and second controlled rectifying elements S ₁ ,
Smoothing capacitors C ₃ and C ₄ and resistors R ₅ and R ₆ are connected between each gate of S ₂ and the ground, respectively.
Further, R ₇ and R ₈ in the figure are discharge resistors that discharge the charges charged in the respective capacitors C ₁ and C ₂ .

Further, the load motor 7 has a structure of a phase advance capacitor type AC motor shown in FIG. That is, in the figure, 14 is an AC power supply, _C5 is a phase advance capacitor, and the relays _M1 and _M2 are connected between both ends of this capacitor _C5 and the power supply 14, respectively.

The operation of the flow rate adjustment system with the above configuration will be explained below.

First, flow rate or temperature information is sent from sensor 1.
The voltage signal is applied to the PID operation circuit 2, where a voltage signal corresponding to the deviation from the target value is applied to one input terminal of the operational amplifier 5. A voltage signal from the potentiometer 4 is applied to the other input terminal of the operational amplifier 5, and the signal from the potentiometer 4 and the signal from the PID operation circuit 2 are compared and calculated by the operational amplifier 5. Depending on the difference, a positive current or a negative current is output and applied to the servo circuit 6.

When a positive current is applied to the servo circuit 6, the current is supplied to the gate of the first controlled rectifier _S1 via the diode _D3 and the resistor _R3 , and the first
The controlled rectifying element S ₁ is turned on, and the relay M ₁ is turned on at the same time. The ON state of this relay _M1 causes the motor 7 to rotate forward and open the flow control valve 8. The potentiometer 4 is also operated in conjunction with the operation of the control valve 8, and when the output signal of the potentiometer 4 becomes equal to the signal of the PID operating circuit 2, the output of the operational amplifier 5 becomes zero, and the first control rectifier When element S ₁ and relay M ₁ are turned off, motor 7
stops. When the first controlled rectifying element _S1 changes from the ON state to the OFF state, the voltage waveform applied to the anode of the first controlled rectifying element _S1 changes from the waveform shown in FIG. 4A to the waveform shown in FIG. 4B. Changes to Therefore, when the first controlled rectifying element _S1 is turned off, a voltage is generated at its anode that allows the forward current of the diode _D1 to flow, and the current of the diode _D1 is transferred to the first current control circuit. 15 to the gate of the second controlled rectifier element _S2 .
The current applied to the gate of this second controlled rectifying element S ₂ is supplied with a delay during the time set by the capacitor C ₁ and the resistor R ₁ of the first time constant circuit 11 in the first current control circuit 15. During this period, the gate of the second controlled rectifier _S2 is
Even if an ON signal is generated, the OFF state will be maintained. In other words, when the output of the operational amplifier 5 suddenly reverses and a negative current is applied to the servo circuit 6, the current flows through the diode _D4 and the resistor _R4 to the gate current of the second controlled rectifier _S2 . However, the current from the first time constant circuit 11 cancels the second controlled rectifying element _S2 .
The OFF state is maintained. When a predetermined period of time has elapsed from this state, charging of the capacitor _C1 is completed, the current in the first time constant circuit 11 is stopped, the second control rectifier _S2 is turned on, and the relay _M2 is turned on at the same time. becomes. This ON state of relay _M2 causes the motor 7 to rotate in the reverse direction and close the flow control valve. Moreover, when the output of the operational amplifier 5 is inverted from this state, the second time constant circuit
A delayed reverse bias current is supplied to the gate of the first controlled rectifier _S1 for a set time, and the first controlled rectifier
The OFF state of _S1 is maintained for a certain period of time.
In this way, when the signal applied to the servo circuit 6 suddenly reverses, switching is performed after the OFF state is maintained for a predetermined period of time, so there is no risk of applying an excessive load to the relay contacts. . Note that the currents supplied through the first and second time constant circuits 11 and 12 are pulsating currents, but are smoothed by smoothing capacitors C ₃ and C ₄ , respectively, and direct current is supplied to each gate. has been done.

In the embodiment described above, an SCR is used as the first controlled rectifying element _S1 , and a PUT is used as the second controlled rectifying element _S2 , but if an inverter is connected to one gate, the first and second controlled rectifying elements SCRs can be used for both of the second controlled rectifying elements S ₁ and S ₂ .

As explained above, according to the present invention, there is a delay time when the load motor rotates forward or reverse, and the forward or reverse rotation occurs after the time necessary for absorbing the inertia of the motor and discharging the phase advance capacitor. This has the effect that there is no risk of excessive current flowing through the relay contacts, and prevention of deterioration and welding of the relay contacts can be achieved with a simple circuit configuration.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a flow rate adjustment system in which a servo circuit according to the present invention is used, Fig. 2 is a circuit diagram showing an embodiment of the servo circuit according to the present invention, and Fig. 3 is a circuit of a load motor. Figure 4A is a waveform diagram of the voltage applied to the control rectifier when the control rectifier is in the ON state, and Figure 4B is a waveform diagram of the voltage applied to the control rectifier when the control rectifier is in the ON state.
FIG. 3 is a waveform diagram of the voltage applied to the control rectifying element during the OFF state. 6... Servo circuit, 9... Alternating current, 11...
first time constant circuit, 12... second time constant circuit,
15...First current control circuit, 16...Second current control circuit, _S1 ...First control rectifier, _S2 ...
Second control rectifier, D ₁ ... first diode (detection circuit), D ₂ ... second diode (detection circuit), M ₁ · M ₂ ... relay.

Claims (1)

[Scope of Claims] 1. A pair of two relays driven by current supplied from a common AC power source, and a current applied to the gate to switch ON and OFF states and supplied to each relay from the AC power source. control the current
A first controlled rectifying element made of an SCR, a second controlled rectifying element made of an SCR or a PUT, and when the first controlled rectifying element is switched to the OFF state, a current flows through the gate of the second controlled rectifying element. A first detection circuit and a first time constant circuit that delay and supply for a predetermined time, turn off a second controlled rectifier during this period, and turn on the second controlled rectifier after the supply ends. When the first current control circuit consisting of the first current control circuit and the second control rectifier are switched to the OFF state, a current is supplied to the gate of the first control rectifier with a delay for a predetermined time, and during this time, the first current control circuit a second current control circuit including a second detection circuit and a second time constant circuit that turns the controlled rectifier into an OFF state and turns the first controlled rectifier into an ON state after the supply ends. A servo circuit characterized by the following configurations. 2. The servo circuit according to claim 1, wherein the first and second current control circuits are configured by a series circuit of a diode, a capacitor, and a resistor.