JPS6062232A - Semiconductor interrupting circuit - Google Patents

Abstract

PURPOSE:To supply the main circuit holding voltage of a cascaded three-terminal bilateral thyristor stably by utilizing the leak current of a transistor (TR). CONSTITUTION:A positive voltage is supplied to a terminal A1 and a negative voltage is supplied to a terminal A2. Then, an NPN TR having a diode connected between the collector and emitter reversely in parallel and the three- terminal bilateral thyristor TC are cascaded. A switch SW is connected between its base terminal B and gate terminal G. This switch SW is turned on and off to form a short circuit between the base and gate, and a base voltage and a gate voltage as driving voltages are generated and applied to respective control electrodes. A resistance R6 is connected between the collector and base and when the thyristor turns off, a stabilized DC voltage is supplied to the switch SW for the base terminal B to supply the main circuit voltage of the thyristor TC stably by utilizing the leak current of TR.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor switching circuit that copes with the generation of induced voltage under a DC voltage source.

When driving an inductive load using a three-terminal bidirectional thyristor, in addition to the drive circuit, a circuit for turning off the thyristor and a circuit for stably supplying a holding current are required. For example, there is a circuit in which a transistor and a thyristor are connected in series. In this case, drive circuits for both the base circuit and the gate circuit are required, and the thyristor is triggered by the main current generated by the transistor operation. Therefore, it has not been possible to obtain higher reliability in terms of asynchronous instability factors, thyristor operational stability, etc.

The present invention was made in view of the above-mentioned problems, and consists of an NPN transistor in which a diode is connected in anti-parallel between the collector and emitter, and a three-terminal bidirectional thyristor connected in cascade. By using this, the thyristor was triggered by the current voltage from the bypassed circuit. As a result, the control electrode base
The holding current for transistor operation was obtained only by opening/closing control by shorting the gate terminals. Furthermore, the power when the thyristor is on and off
Since the transistor operation was compensated for, the reverse voltage was returned to the power supply side without difficulty, and from this, a stable supply of holding current was achieved. That is, the present invention provides a highly reliable semiconductor switching circuit that can cope with induced voltage under a DC voltage source.

Hereinafter, the present invention will be explained in detail with reference to embodiment circuits shown in the drawings.

FIG. 1 shows the basic circuit of the invention.

The DC voltage across the load causes a positive voltage at the A1 terminal and a positive voltage at the A2 terminal.
Apply and supply negative voltage to the terminal. TR is N with diodes (D) connected in antiparallel between the collector and emitter terminals.
It is a PN type transistor, with a collector (C) and a base (
B), has an emitter (E) terminal. TC is a three-terminal bidirectional thyristor (hereinafter simply referred to as a thyristor),
It has an electrode (T2), an electrode (T1), and a gate (G) terminal. The emitter (E) terminal and the electrode (T2) are cascade-connected, and this transistor cascade-connected thyristor (TR/TC
), the base (B) terminal and gate (G)
A switch (SW) is connected between the terminals. By controlling the opening and closing of this sweetener (SW) and shorting between the base and gate, a base voltage (∇b) and a gate voltage (∇g), which are drive voltages, are generated, and each control pole (B, G) is Apply and supply. A resistor (R6) is connected between the collector and base (
For example, when the thyristor is turned off, it supplies the stabilized DC voltage to the base (B) terminal and the switch (SW), and supplies the stabilized DC voltage to the base (B) terminal and the switch (SW). By using the leakage current, the main circuit voltage (∇t2) of the thyristor (TC) is stably supplied. When the transistor cascade-connected thyristor (TR/TC) is turned on, (R6) is a resistor that limits the current.

With this configuration, the thyristor (TC) in which the trigger mode is selected is connected to the main circuit voltage (∇t2) supplied using the base leakage current and the base-gate voltage (
∇b, ∇g) is triggered by a drive voltage from a switch (SW) and turns on. This trigger voltage (∇t2・∇b
・∇g) uses the shunted resistor (R6) as a supply source, so it not only stabilizes the main circuit voltage but also prevents malfunctions due to erroneous firing. That is, by supplying sufficient main circuit voltage (∇t2) using the leakage current at the base of a transistor (TR) selected or newly created according to the purpose, the main circuit voltage can be synchronized. The thyristor (T
C) can be reliably triggered and stably triggered.

This will be explained in detail below using the example in FIG.

A commercial frequency power source (AC) passing through a load (L) is full-wave rectified by a diode bridge (BR), and supplies positive and negative DC voltages to terminals A1 and A2, respectively. In order to intermittent this DC voltage, a transistor cascade-connected thyristor (TR/TC) and a switch (SW) are connected as shown. This switch (SW) has a capacity (C9
) A connection resistor (R9) and a connection switch element (SW) are used to make the supply voltage non-inductive. R9a is the capacity (C9)
is a starting resistor connected in parallel with M, and M is a pulse transformer. Note that Z is a surge absorber for dv/dt suppression, and is connected between A1 and A2 terminals.

With such a configuration, the thyristor (TC) to which the main circuit voltage (∇t2) is stably supplied will have the aforementioned drive voltage (
The cathode current (It1) is triggered and turned on in response to the supply of ∇g and ∇b), and is limited by the aforementioned resistor (R6).
flow. When this cathode current (It1) flows, the transistor (TR) is turned on, and a main current, which is a collector current, flows. In other words, since the cathode current (It1) increases in proportion to the drive current (IgIb), the base current (Ib) can be input very easily by controlling the opening and closing of the switch (SW), and the transistor operation can be controlled. A holding current (It2), which is the connection capacitance, can be obtained. This holding current (
When It2) decreases, the thyristor (TC) is turned off, and subsequently the transistor (TR) is turned off. Below, the transistor cascade-connected thyristor (T
R・TC) will continue. That is, by using the leakage current of the base, all the voltage for triggering the thyristor (TC) was supplied from the bypassed circuit (R6), so the trigger operation was extremely stable, and the switch (SW) A base current of (Ib) corresponding to the short-circuit capacity of .

Referring to FIG. 3, the continuous operation will be further explained using an example of a circuit that generates an induced voltage.

Unlike the example in Fig. 2, a smoothing capacitor (C1) is connected between the DC output terminals of the diode bridge (BR) as shown in the figure, and this DC smoothed voltage is applied to the A1 and A2 terminals respectively through loads (L1L2). is applied and supplied.

The following is a summary. When driving the load (L1L2), two basic circuits of the example in FIG. 1 are connected as shown. and,
By shifting the phase of the switch (SW1) and switch (SW2) (for example, driving SW2 earlier or later than SW1) and controlling the opening and closing in each forward and reverse direction alternately, a thyristor (TC) with bidirectional characteristics can be created. is each triggered to drive. Hereafter, when the forward current is cut off, a surge voltage and an induced voltage are generated. The surge voltage is divided and absorbed by the diode (D) and the bypassed circuit described above, and this surge voltage is used to cause the base current flowing from the base to be absorbed by the bypassed circuit. Further, the induced voltage is applied to the thyristor via the diode (D), and by driving the thyristor (TC) in the reverse direction, it is easily returned to the power supply side. That is, the diode (D
) safely returns the reverse voltage generated by surge voltage or induced voltage to the power supply side to prevent transistor destruction and noise generation, and also ensures a base current that responds quickly to the state of the inductive load.

As mentioned above, if a transistor and a three-terminal bidirectional thyristor are connected in cascade and the leakage current at the base of the transistor is used, the thyristor is triggered and turned on by the bypassed DC voltage, and the transistor is turned on by the current flow. let As a means of achieving this, simply by controlling the opening and closing of the switch connected between the base and gate, a holding current, which is the connection capacitance of the transistor, can be obtained, and the DC voltage can be switched on and off at will. or,
By connecting a diode in anti-parallel between the collector and emitter, the bidirectional characteristics of the thyristor and the power during intermittent operation can be improved.
It becomes possible to match transistor operations. From this, it is possible to automatically and safely supply a holding current that immediately corresponds to the operating state of the load. Prevents malfunctions due to erroneous ignition. An extremely reliable continuity circuit has been created that prevents noise generation and heat generation, and can be used, for example, as a power control circuit in inverters, converters, cycloconverters, etc.

[Brief explanation of drawings]

FIG. 1 shows the basic circuit of the present invention. FIG. 2 is an example of a specific drive circuit diagram. FIG. 3 shows an example of a drive circuit diagram of a load that generates an induced voltage. In the drawing, TR is an NPN transistor, D is a diode, TC is a three-terminal bidirectional thyristor, SW is a switch, R6 is a current limiting resistor, L is a load, BR is a diode bridge, and Z is a surge absorber. .

Claims (1)

[Claims] (1) By cascading an NPN transistor with diodes connected in antiparallel between the collector and emitter and a three-terminal bidirectional thyristor, and utilizing the leakage current of the base of the transistor, the three-terminal bidirectional A semiconductor intermittent circuit characterized by supplying a holding current of a thyristor.