JPS5937896B2 - AC power semiconductor switch device control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control circuit for a semiconductor switch device I that supplies and cuts off alternating current power to a load.

It is advantageous to use semiconductor switches as switches for alternating current power, and by turning on and turning off such switches when the instantaneous voltage value passes through zero, radio frequency interference can be eliminated. It has been known.

In addition, optical coupling of on/off control signals to the control circuit of such a switch is advantageous because complete direct current isolation can be obtained and malfunction of the device due to noise etc. can be prevented. is also known.

Conventionally, as described above, a semiconductor switch device control method uses optical coupling of on/off control signals and turns the switch on and off when the instantaneous voltage value passes through the zero point. Although various circuits have been proposed, all of them have the drawback of requiring a large number of circuit components and having a complicated configuration.

OBJECT OF THE INVENTION (iii) It is to provide a control circuit for an AC power semiconductor switch device that requires a small number of circuit components and has a simple configuration.

The present invention will be described below with reference to the drawings showing preferred embodiments thereof.

FIG. 1 is a diagram showing the basic circuit of the present invention, which includes a resistor R1, a light emitting diode LED, and a light emitting diode LED connected as shown.
Protection diode D1, optical variable resistance element P which is a light receiving element
C, resistor R2, NPN transistor TR1, PNPI
- It consists of a run risk TR2, characteristic elements A and s having characteristics as described below, and a triac TRIAC as a gate control semiconductor device.

Note that TI and T2 are the terminals of the triac, G is the gate of the triac, and P.

N indicates a DC input terminal, ACl and AC2 indicate AC power terminals, and one of these AC power terminals is a load (not shown).
Connected to one terminal of the AC power supply through the

The light emitting diode LED and the optical variable resistance element PC form a photocoupler.

As the gate control semiconductor switch device, any semiconductor device other than a TRIAC can be used as long as it has bidirectionality and is turned on and off by a gate current. Combinations etc. can also be used.

As shown in Fig. 2, the characteristic element A is such that when a voltage V is applied, the current increases by 1 as the absolute value of the voltage increases, but
Current■.

Once it reaches 1, the voltage increases beyond that point, but then decreases as the absolute value of the voltage increases, and the absolute value of the voltage becomes ■.

At a voltage higher than that, almost no current flows and the voltage becomes non-conductive.
It is an element with current characteristics.

An element having the characteristics shown in FIG. 2 can be realized, for example, by combining four junction field effect transistors as shown in FIG. 3.

In FIG. 3, Dε and S represent four junction field effect transistors FET1, FET2, FET3.

The respective drain and source electrodes of FET 4 are shown.

Note that, as will be understood from the explanation of the circuit shown in FIG. 1 later, the characteristics of the characteristic element A are strict, and ti IJ: <
, generally speaking, a positive or negative current will flow for an applied positive or negative voltage that is lower than that value, but no current will flow for an applied positive or negative voltage that is greater than or equal to that value. It has a voltage-current characteristic such that no current flows, and the current that flows turns the gate-controlled semiconductor switch device into an on state.
It is sufficient if the size is large enough for switching.

Next, the operation of the circuit shown in FIG. 1 will be explained.

When no DC input signal is applied to terminal P, the light emitting diode LED does not emit light, and the optical variable resistance element PC does not receive light, so there is a high resistance state 1, and the transistor TR
I and TR2 conduct base current through the resistor R2 during the positive and negative half cycles of the AC power supply, so they remain in the on state. Therefore, even if current flows through the characteristic element A1, the current flows to the TRIAC side. No flow
As the transistors TR1 and TR21 flow, the triac TRIAC does not turn on, and AC power is not supplied to the load 1.

Next, a DC input signal is applied to the terminal P, and the AC voltage applied to the triac TRI ACi is + as shown in Fig. 2.
When Vo or -■ is low, characteristic element A flows current according to the voltage characteristics shown in Figure 2, while the light emitting diode LED emits light, and the optical variable resistor PC receives the light and enters a low resistance state. Therefore, the base currents of transistors TR1 and TR2 do not flow, and therefore these transistors TR1 and TR2 do not flow.
TR2 remains in the off state, and current from characteristic element A flows through the gate of the triac TRIAC, turning it on and providing AC power to the load.

AC voltage is +Vo or -V.

In the above case, since the characteristic element A does not conduct direct current, the transistors TR1 and TR2 are supplied with a direct current input signal.
Even if there is an off state, the triac TRIA
No current is supplied to the gate 1 of C, so the triac TRIAC does not turn on.

As mentioned above, the conditions for the TRIAC to turn on are that the current input signal is applied and the AC voltage is applied to the second
+■o or -V in the diagram.

TRIAC TRIAC TRIAC The intended purpose of turning off can be achieved.

Since the triac automatically turns off when the current between its terminals becomes less than the minimum holding value in a state where no gate current is applied, the triac can be turned off when the instantaneous voltage value passes the zero point.

FIG. 4 is a circuit diagram of a semiconductor switch device control circuit that is actually used. Here, in order to increase the current gain, one transistor TR1i is replaced with a transistor TR38 and a resistor R3. A transistor TR48 and a resistor R4 are added to the transistor TR,2, and a combination of diodes D2 to D4 is added to increase the noise margin for the triac TRIAC and ensure its on/off operation. It has been added.

FIG. 5 is a diagram illustrating the actual characteristics of the characteristic element A.

As understood from the above description, the present invention provides a control circuit for an AC power semiconductor switching device that requires a small number of circuit components and has a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the basic circuit of the semiconductor switch device control circuit of the present invention, FIG. 2 is a diagram showing an example of voltage-current characteristics of a characteristic element, and FIG. 3 is a diagram showing the voltage-current shown in FIG. FIG. 4 is a diagram showing an example of an actual circuit of a semiconductor switch device control circuit, and FIG. 5 is a diagram illustrating actual characteristics of the characteristic element. ACI, AC2... AC power supply terminal, TRIAC
...Triac, TI, T2...Triac terminal, G...Triac gate, A...Characteristic element, Trl...NP
P transistor, Tr2...PNP transistor,
PC... Optical variable resistance element, LED...
light emitting diode,

Claims (1)

[Scope of Claims] 1. A bidirectional gate-controlled semiconductor switch connected in series through an AC input power supply and a positive or negative applied voltage lower than the value of the load. The gate-controlled semiconductor switch device is connected between one terminal of the gate-controlled semiconductor switch device and has a voltage-current characteristic such that a current flows through the gate, but no current flows in response to a positive or negative applied voltage equal to or higher than the above value. and a switching circuit connected between the other terminal and the gate of the gate-controlled semiconductor switching device, and the switching circuit includes a PNP, an E-type transistor, and a switching circuit connected between the gate and the other terminal of the gate-controlled semiconductor switching device.
and an NPN transistor, and a series circuit of an optical variable resistance element optically coupled to a light emitting element provided in a control input circuit, and a fixed resistor, wherein the collector and emitter terminals of the pNps and NPN transistors are connected to the gate control semiconductor. The light variable circuit is connected between the other terminal gate of the switch device, the series circuit is connected in parallel to the gate control semiconductor switch device, and the light variable circuit is responsive to light from a light emitting element provided in the control input circuit. The on/off of the PNPa and NPN transistors is controlled by the voltage between the terminals of the resistive element, and when a human power signal is applied to the control input circuit, the switching circuit is switched to an off state; A semiconductor switch for AC power, characterized in that when an AC input power supply voltage is below the value, a current from the characteristic element flows into the gate of the semiconductor switch device, thereby rendering the semiconductor switch device conductive. Device control circuit. 2. A control circuit for an alternating current power semiconductor switch device, in which the gate control semiconductor switch device is composed of a triac in the control circuit according to claim 1. 3. Claims 1 or 2 (f) In the control circuit described herein, the characteristic elements include four junction field effect transistors, and the two field effect transistors have drain electrodes adjacent to each other. The two outer field effect transistors connected to each other are connected in series so that the source electrodes of the adjacent field effect transistors are connected to each other, and the drain electrodes of the inner two field effect transistors are connected to the outer two electric fields. The gate electrodes of the two inner field effect transistors are connected to the drain electrodes of the adjacent field effect transistors, and the terminals of the characteristic elements are drawn out from the drain electrodes. A semiconductor switch device control circuit for AC power.