JPS5856529A - Semiconductor solid-state relay - Google Patents

Abstract

PURPOSE:To obtain a large output, using a semiconductor control rectifier of a small capacity, through the connection of an input terminal of a full-wave rectifier circuit to one terminal of an AC power supply and a plurality of semiconductor controlling rectifiers connected to the AC power supply. CONSTITUTION:When an input signal is applied to terminals 9 and 10, a photothyristor SCR2 receives a light trigger signal of a light emitting diode 3 but since a transistor TR12 turns on with a high power supply voltage and the gate and cathode of the SCR is short-circuited, the SCR2 is not turned on. When the power supply voltage comes close to zero volt, the TR12 is turned off, the SCR2 is triggered and pulsive currents are applied to the gate of Triacs TAC19, 20 via a full-wave rectifier circuit 1 to trigger both the TACs. When the polarity of the power supply voltage is changed, the TR12 is turned off until the base potential of the TR12 reaches a constant value and a current flows to the gate of the TAC19, 20, the circuit 1 and the SCR2 and the TAC19, 20 remained being triggered and an AC load current flows. Through the use of a plurality of TACs, the load current of large capacity can be controlled.

Description

[Detailed Description of the Invention] The present invention relates to a semiconductor solid state relay, and an object of the present invention is to provide a semiconductor solid state relay that can obtain a large capacity output using a small capacity semiconductor controlled rectifier. However, a first semiconductor-controlled rectifier is connected between the output terminals of the full-wave rectifier, and this semiconductor-controlled rectifier has an ignition means and a control terminal that connects the full-wave rectifier when the output voltage of the full-wave rectifier becomes approximately zero. The full-wave rectifier circuit has short-circuiting means for breaking short-circuits between the terminals, one input terminal of the full-wave rectifier circuit is connected to one end of the AC power supply, and the other input terminal is connected to a plurality of second semiconductor-controlled rectifiers connected to the AC power supply. It is connected to each control terminal of the device.

The present invention will be explained below with reference to an embodiment shown in the drawings.

In FIG. 1, reference numeral 1 denotes a full-wave rectifier circuit, and a photothyristor 2 is connected between its output terminals. The photothyristor 2 is photocoupled with a light emitting diode 3, and the light emitting diode 3 is connected to a constant current circuit consisting of resistors 4 and 5 and a transistor 6.7, and a DC signal input terminal 9 through a diode 8.
10. A resistor 11 is connected between the gate and cathode terminals of the photothyristor 2. A transistor 12 is connected and is driven by voltage dividing resistors 13, 14, 15 and a capacitor 16 provided between the output terminals of the full-wave rectifier circuit 1. One input terminal of the full-wave rectifier circuit 1 is connected to one terminal 17 of the AC power supply, and the remaining input terminals are connected to the gate terminals of two triacs 19.20 provided between the AC power supply terminals 17.18. ing. A resistor 21 and a capacitor 22 constitute a snubber circuit for triacs 1.9 and 20. Although the load is not shown, it is provided between the AC power supply terminals 17 and 18 and the AC power supply.

The operation of the illustrated solid-state semiconductor relay will be briefly explained together with the waveforms shown in FIG.

As shown in Fig. 2(a), when no input signal is applied to input terminals 9 and 10, terminals 17 and 18 are connected to terminals 17 and 18 as shown in Fig. 2(b).
Even if a power supply voltage indicated by
, 20, no firing signal is applied to the triacs 19, 20,
20 remains off and no load current flows.

When an input signal is applied, the photothyristor 2 receives a light ignition signal from the light emitting diode 3, but when the power supply voltage is high, the transistor 12 is in the on state and the gate and cathode terminals are short-circuited, so there is only one point. No arc. When the power supply voltage decreases to near zero volts, the voltage level of the transistor 12 also decreases, turning off the transistor 12 and releasing the short circuit between the gate and cathode terminals of the photothyristor 2. For this reason, the photothylisk 2 is ignited, the pulsating current through the full-wave rectifier circuit 1 is applied to the gate terminal of the triac 19.20, and both triacs 19.20 are ignited. When the polarity of the power supply voltage changes 1 Until the base potential of the transistor 120 reaches a constant value r.

The transistor 12 is in an off state, and during this time current flows through the gate terminals of the triacs 19 and 20, the full-wave rectifier circuit 1, and the photothyrist 2, so that the triac 1
9.20 fires. 1), when the ignition signal is applied to the input terminals 9 and 10, the ignition signal 19.
20 continues to fire, and an alternating current load current flows as shown in FIG. 2(C).

When the ignition signal is no longer applied from the input terminals 9 and 10, the load current flows for a half-wave period, and then the photothyristor 2
, the triacs 19 and 20 remain off, so that no current flows. That is, this solid-state semiconductor relay waits until the power supply voltage becomes close to zero volts as the input signal turns on and off, and then the load current stops flowing and is cut off.

The capacity in such a semiconductor solid state relay is determined by the capacity of the triac 19,20 that controls the load current.

In the present invention, 2 iti! of triac 19, 20! i
1 and controlled by a common gate firing signal. This has made it easier to obtain triacs by using two small-capacity triacs instead of the conventional single large-capacity triac that was used to accommodate larger load currents. The aim is to obtain a semiconductor solid-state relay. It is difficult to obtain a large-capacity triac, and the difficulty increases as the capacity increases. In the present invention, since a plurality of triacs are connected in parallel, there is no difficulty in obtaining them.

! In addition, since the same gate firing signal is used, as long as the characteristics of the triacs match, the load current will not be concentrated on some triacs. If the number of try books is increased, it is possible to control a larger capacity load current, and it is easy to make this solid-state semiconductor relay into a single product.

The triacs 19 and 20 may be thyristors connected in antiparallel. Furthermore, the ignition signal for the photothyristor 2 may be an electrical signal that does not use a photocoupler.

[Brief explanation of the drawing]

FIG. 1 is a circuit connection diagram of a semiconductor solid state relay showing an embodiment of the present invention, and FIG. 2 is a diagram showing current and voltage waveforms in the main parts of the semiconductor solid state relay shown in FIG. 1.

Claims (1)

[Claims] 1. A first semiconductor-controlled rectifier is connected between the output terminals of the full-wave rectifier circuit. a plurality of second semiconductor-controlled rectifiers, each having a short-circuiting means for breaking a short-circuit between the terminals, one input terminal of the full-wave rectifier circuit being connected to one end of the AC power supply, and the other input terminal being connected to the AC power supply; A semiconductor solid-state relay, characterized in that it is connected to each control terminal of.