JPH0258860B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit for controlling the gate of a short-circuiting thyristor connected in parallel with an inrush current limiting resistor in a capacitor input type rectifier circuit.

In a capacitor input type rectifying and smoothing circuit,
An inrush current limiting resistor is inserted to suppress the inrush current when the power is turned on, but if this is done alone, the resistor will cause unnecessary power loss and heat generation during normal operation, so a resistor shorting thyristor is connected in parallel to the resistor. A configuration has been adopted in which

An example of such a conventional circuit is shown in FIG. Electric power from an AC power source 1 is supplied to a rectifier diode bridge 3 via a switch 2, smoothed by a smoothing capacitor 4, and then supplied to a load 5 (for example, a switching regulator circuit, etc.). A resistor 6 is an inrush current limiting resistor, and a thyristor 7 is connected in parallel to it. Gate control of this thyristor 7 is performed by directing power from the AC power supply 1 to the auxiliary transformer 8, rectifier diodes 9a, 9b,
This is done by a signal generated via a rectifying capacitor 10 and a delay integration circuit 13 consisting of a resistor 11 and a capacitor 12. In addition, the code 14 is
This is the gate termination resistance of the thyristor.

In other words, this circuit detects power-on by the auxiliary transformer 8 and converts the time constant circuit (delay integration circuit 13).
The gate of the thyristor 7 is controlled by the thyristor 7, and the turn-on of the thyristor 7 is delayed. For this reason, the auxiliary transformer 8 is required above all, which increases the size of the gate control circuit, and since a considerable amount of thyristor gate current is always consumed, the resulting power loss cannot be ignored.

Also, if the load is a switching regulator, the power start signal may be generated from the main switching transformer rather than from the AC auxiliary transformer, but this will make the circuit extremely complicated and the same process as above will occur. The problem remains unresolved. Alternatively, it is possible to generate the startup signal from the smoothing capacitor, but simply applying the above-mentioned conventional technology would not allow the time constant of the delay integration circuit to be large due to the high voltage, and furthermore, the power consumption would increase. This would be impractical in practice as it would become large.

The purpose of the present invention is to eliminate the above-mentioned drawbacks of the conventional technology, to achieve high efficiency by reducing current consumption, to reduce costs by not requiring a transformer, to be unaffected by fluctuations in input voltage, and to reduce gate voltage. The object of the present invention is to provide a very simple and economical thyristor gate control circuit that can automatically follow temperature characteristics.

In order to achieve such an object, the thyristor control circuit of the present invention is a circuit that controls a short-circuit thyristor connected in parallel to an inrush current limiting resistor connected in series to a capacitor input type rectifying and smoothing circuit. , a switching element whose input/output terminal is connected between the anode and gate of the short-circuiting thyristor, a resistor connected in series between the rectifying and smoothing circuit and a control terminal of the switching element, and a switching element of the switching element. and a delay integration circuit which is made up of a capacitor connected in parallel between a control terminal and an output terminal, and which turns on the switching element with a delay after power is turned on to the rectifier and smoothing circuit, and when the short-circuit thyristor is turned on. The gist of the present invention is to supply a gate current to the short-circuiting thyristor via the switching element by a voltage drop across the inrush current limiting resistor when the inrush current is not in operation, thereby turning on the short-circuiting thyristor.
By inserting a switching element between the gate and anode of the resistor shorting thyristor, the control current can be made very small. Therefore, the starting signal can be generated from the main line smoothing capacitor, and the gate turn-on current of the thyristor can be generated. can be supplied from its own anode side. A thyristor, a transistor, or the like may be used as the above-mentioned switching element.

Hereinafter, the present invention will be explained in detail based on the drawings.
FIG. 2 is a circuit diagram showing an embodiment of the present invention,
Components other than the gate control circuit are the same as those shown in FIG. 1, and are given the same reference numerals. That is,
Electric power from an AC power supply 1 is supplied to a rectifier diode bridge 3 via a switch 2, smoothed by a smoothing capacitor 4, and then supplied to a load 5. An inrush current limiting resistor 6 is connected in series to such a capacitor input type rectifying and smoothing circuit, and a main thyristor 7 for resistor shorting is connected in parallel to the inrush current limiting resistor 6.

Connected between the anode and gate of the main thyristor 7 are the input/output terminals, ie, the anode and cathode, of a sub-thyristor 20, which is a switching element. Further, a resistor 21 is connected in series between this rectifying and smoothing circuit and the control terminal, that is, the gate, of the sub-thyristor 20, while a capacitor 22 is connected in parallel between the gate and cathode of the sub-thyristor 20. . A starting signal is generated from the smoothing capacitor 4 by a delay integration circuit 23 composed of the resistor 21 and the capacitor 22. Note that the resistances indicated by reference numerals 24 and 25 are gate termination resistances of the main thyristor 7 and the sub-thyristor 20, respectively.

This circuit operates as follows. When power-up is initiated by turning on switch 2,
The alternating current power is rectified by the rectifier diode bridge 3, and charges are accumulated in the smoothing capacitor 4. The rush current (rush current) during this period is limited by the rush current limiting resistor 6. The resistance value of this inrush current limiting resistor 6 depends on the conditions of use, the capacity of the smoothing capacitor, etc., but a value such as 4.7Ω is usually selected, for example. After being delayed by the delay integration circuit 23 consisting of the resistor 21 and the capacitor 22 for the time necessary to charge the smoothing capacitor 4 with their time constants, the gate current is supplied to the gate of the sub-thyristor 20, and the gate current is supplied to the gate of the sub-thyristor 20. turn on. At this time, the anode current of the sub-thyristor 20 flows due to the voltage drop across the rush current limiting resistor 6 caused by the slight charging current of the smoothing capacitor 4 and the current flowing through the load 5 . As described above, since the cathode of the sub-thyristor 20 is connected to the gate of the main thyristor 7, the gate of the main thyristor 7 is turned on. At the same time, most of the current flowing through the inrush current limiting resistor 6 becomes an anode current of the main thyristor 7, and both ends of the inrush current limiting resistor 6 become in a state similar to being short-circuited. As a result, the anode current of the sub-thyristor 20, that is, the gate current of the main thyristor 7, decreases;
The turned-on state is maintained until the anode current of the main thyristor 7 becomes equal to or less than the holding current of the thyristor. Because of this effect, once the power is turned on, the device automatically repeats on and off depending on the value of the load current determined by the gate turn-on current of the thyristor and the holding current of the thyristor. In other words, when the load is light (when the current drops below the holding current of the thyristor), the thyristor turns off again, but the current consumption of the resistor 6 at this time is small, and when the load shifts to a heavy load, the main thyristor 7 turns on. Sufficient gate current flows and the main thyristor 7 is turned on again. For example, in general, the gate current of the main thyristor 7 is required to be about 35 to 36 mA, but in the case of a two-stage thyristor configuration as in this embodiment, the gate current of the sub-thyristor 20 is
Approximately 0.5mA is sufficient. As mentioned above, 35mA
Since the gate current of the main thyristor 7 is supplied by the voltage drop across the resistor 6, the current required to control this thyristor is essentially 0.5m.
This means that power consumption can be reduced, and it is also possible to obtain a starting signal from the smoothing capacitor 4.

Although not shown, if a noise suppressor capacitor is inserted in parallel with the termination resistor 24 at the gate of the main thyristor 7, it is possible to more completely suppress the thyristor from turning on due to thin pulse noise. Furthermore, it is preferable to insert a series circuit of an anode current limiting resistor and a reverse current blocking diode on the anode side of the sub-thyristor 20.
If there is no diode, the gate current will flow to the anode side at light loads, but there is no guarantee for this current in the device, so inserting a diode can prevent the gate current from flowing to the anode side. It is from.

As a switching element for driving the main thyristor 7, a transistor 20' is used as shown in FIG.
It is also possible to use This is because, once the main thyristor 7 is turned on, it will continue to be turned on even if the gate current disappears, as long as an anode current greater than the holding current flows.

Although preferred embodiments of the present invention have been described above, it goes without saying that various changes can be made within the scope of the present invention when implementing the present invention.

Since the present invention is a thyristor control circuit configured as described above, current consumption is reduced and efficiency is high, and a transformer is not required, so the device can be miniaturized.
It has many excellent effects, such as being able to simplify and reduce costs, and also enable reliable gate control of the thyristor without being affected by input voltage fluctuations or the temperature characteristics of the thyristor.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional technique, FIG. 2 is a circuit diagram showing an embodiment of the present invention, and FIG. 3 is an explanatory diagram of main parts of another embodiment of the present invention. 1... AC power supply, 2... Switch, 3... Rectifier diode bridge, 4... Smoothing capacitor, 5
...Load, 6...Inrush current limiting resistor, 7...Main thyristor, 20...Sub-thyristor, 20'...Transistor, 23...Delay integration circuit.

Claims (1)

[Scope of Claims] 1. A circuit for controlling a short-circuiting thyristor connected in parallel to an inrush current limiting resistor connected in series to a capacitor-input type rectifying and smoothing circuit, the circuit comprising: a switching element having input/output terminals connected to the switching element; a resistor connected in series between the rectifying and smoothing circuit and a control terminal of the switching element; and a resistor connected in parallel between the control terminal and the output terminal of the switching element. and a delay integrating circuit that turns on the switching element with a delay after the power is turned on to the rectifying and smoothing circuit, the circuit comprising a connected capacitor; A thyristor control circuit in an inrush current limiting circuit, characterized in that a voltage drop supplies a gate current to the shorting thyristor via the switching element to turn on the shorting thyristor. 2. The thyristor control circuit according to claim 1, wherein the switching element is a thyristor or a transistor.