JPS6135017A - Switching control circuit - Google Patents

Abstract

PURPOSE:To speed up the switching speed, to stabilize the operation, to reduce number of components and to attain ease of electric insulation of the titled circuit by controlling the switching element through the changeover of rectifying polarity of an AC power supply. CONSTITUTION:An output voltage of an AC power supply 2 is fed to a switching transistor TR10 via a current direction switching means 4, a voltage smoothing capacitor C6, and a current limit resistor R8. The current direction of the means 4 is switched by an external signal and a voltage having a selected polarity is fed to the C6. When a positive voltage is applied to the C6, the TR10 is turned on and when a negative voltage is applied to the C6, the TR10 is turned off and its base is reverse-biased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a switching control circuit for controlling switching elements such as transistors and thyristors.

[Background of the invention]

Conventional base control circuits that control the switching of switching elements, such as transistors, use two positive and negative power supplies with the emitter of the transistor as a reference potential, which increases the switching speed of the transistor and ensures operational safety. However, the disadvantages are that the circuit has a large number of components, resulting in a complex configuration, and in the case of insulating the base control circuit, a large number of auxiliary power supplies are required.

In addition, in the case of a single power supply, a capacitor was used in parallel with the base resistor to increase the switching speed of the transistor, but there was a problem with operational stability in that the base did not become reverse biased when it was off.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a switching control circuit that increases the switching speed of a switching element and stabilizes its operation, can be configured with a small number of parts, and can easily electrically insulate the circuit.

[Summary of the invention]

A feature of the present invention is that switching control of switching elements is realized by switching the rectification polarity of an AC power supply supplied as a control power supply.

In other words, the two positive and negative power supplies necessary for increasing the switching speed and stable operation of the switching element can be configured with a single-phase half-wave rectifier circuit, but the two power supplies do not need to coexist for switching the switching element, and the switching operation It is sufficient if a voltage with the polarity required for the mode (on, off) can be applied to the control input terminal of the switching element.

Therefore, a switching control circuit can be formed by switching the rectification polarity of the rectifier circuit in accordance with the operating mode of the switching confectionery.

[Funny example of invention]

An embodiment of the present invention will be explained below with reference to FIG. That is, a series circuit is provided in which the first terminal of the current direction switching means 4 and the first terminal of the current limiting means 8 are connected. The second terminal of the current direction switching means 4 is connected to the first terminal of the AC voltage generation means 2.
The second terminal of the current limiting means 8 is connected to the pace of the transistor 10. AC voltage generating means 2
A second terminal of is connected to the emitter of transistor 10.

A first capacitor 6 for voltage smoothing is connected between the first terminal of the current direction switching means 4 and the second terminal of the AC voltage generating means.

The operation of the circuit will be explained below. An alternating current voltage is generated between the first terminal and the second terminal of the alternating current voltage generating means, and when the second terminal is set to a reference potential, the polarity of the voltage applied to the first capacitor is changed. is determined by the current direction selected by the current direction switching means 4 which switches the stain flow direction in response to an external signal.

When a positive voltage is applied to the first capacitor 6, the current limited by the current limiting means 8 flows through the transistor 10.
, and the transistor 10 is turned on.

Conversely, when a negative voltage is applied to the first capacitor 6, the current limited by the current limiting means 8 is sucked out from the pace of the transistor IO, turning off the transistor 10, and turning off the pace of the transistor 100. Set to reverse bias state.

Although FIG. 1 describes the case of an NPN transistor, a similar circuit can be used for switching elements such as a PNP transistor, FET, and thyristor.
Switching can be controlled. Furthermore, if insulated components are used for the AC voltage generation means 2 and the current direction switching means 4, for example, a transformer is used as the AC voltage generation means, and a photodiode, phototransistor, photothyristor, etc. is used as the current direction switching means, switching control can be achieved. The circuit can be insulated. FIG. 2 is a circuit diagram showing an example thereof.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the switching element can be switched without requiring a bipolar power supply, and the control input terminal can be put in a reverse bias state, so fewer components are required. It has the advantage of being able to realize high-speed and stable switching operation with a simple number of points and a simple circuit configuration, and is advantageous in terms of reliability and economy. Further, by selecting the circuit components, an isolated circuit can be easily constructed.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, and FIG. 2 is a circuit diagram described using specific elements. 2... AC voltage generating means, 4... Current direction switching means, 6... First capacitor, 8... Current limiting means,
lO...Transistor.

Claims (1)

[Claims] A series circuit of current direction switching means and current control means is disposed between the AC voltage generation means and the control input terminal of the switching element, and the current direction switching means is connected to the AC voltage generation means, and the AC voltage is A switching control circuit comprising: a reference potential side of the generating means connected to a control reference voltage terminal of the switching element; and a capacitor connected between the reference potential side and a common connection portion of the series circuit.