JPS5812571A - Thyristor control circuit in rush current limiting circuit - Google Patents

Abstract

PURPOSE:To prevent the wasteful power loss at a resistor by inserting an amplifying element between the gate and the anode of a resistor shortcircuiting thyristor. CONSTITUTION:When a power source 1 is energized, a rush current limited by a resistor 6 is flowed through a smoothing condenser via the resistor 6 to charge the condenser. An amplifying element 20 is gated after the prescribed period of time by a delay integrating circuit 23 and is turned ON, a resistor shortcircuiting thyristor 7 is then turned ON, and most of the current flowing through the resistor 6 is flowed through the thyristor 7. In this manner, the current flowing through the resistor 6 is reduced, thereby preventing the wasteful power loss.

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 rectifier and smoothing circuit, a limiting resistor is inserted on the inrush current side to suppress the inrush current when the power is turned on, but if this is done alone, the resistor will cause unnecessary power loss 2 and heat generation during normal operation. , a configuration is adopted in which a resistor shorting thyristor is connected in parallel to the resistor.

An example of such a conventional circuit is shown in Figure 1.1.

The power from the AC power supply 1 is supplied to a rectifier diode bridge 3 via a switch 2, smoothed by a smoothing capacitor 4, and 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.

The gate control of the thyristor 7 is performed by a signal generated by transmitting power from the AC power source 1 through an auxiliary transformer 8, rectifying diodes 9a, 9b, a rectifying capacitor 10, and a delay integrating circuit 13 consisting of a resistor 11 and a capacitor 12. done by.

In addition, the code|symbol 14 is the gate termination resistance of a thyristor.

That is, in this circuit, the auxiliary transformer 8 detects power-on, and the time constant circuit (delay integration circuit 13) controls the gate of the thyristor 7, thereby delaying the turn-on of the thyristor 7. For this reason, the auxiliary transformer 8 is required above all else, which increases the size of the gate control circuit.
Furthermore, 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 supply start signal may be generated from the main switching transformer rather than from the AC auxiliary transformer mentioned above, but this makes the circuit extremely complex and has the same problems as above. Still 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 practically impossible 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, according to the present invention, the control current can be small by inserting an amplifying element between the gate and anode of the resistor shorting thyristor, and therefore the starting signal is transmitted from the main line smoothing capacitor. The present invention is characterized by the fact that the gate turn-on current of the thyristor is supplied from its own anode side.

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, in which the same circuit as shown in FIG. 1 is adopted except for the gate control circuit.
The same reference numerals are given. That is, power from the AC power source 1 is supplied to the rectifier diode bridge 3 via the switch 2, smoothed by the smoothing capacitor 4, and then supplied to the load 5. In such a capacitor input type rectifying and smoothing circuit, an inrush current limiting resistor 6 and a main thyristor 7 for resistor shorting are connected in parallel to the inrush current limiting resistor 6.

A sub-thyristor 20 is connected as an amplifying element between the gate and anode of the main thyristor 7, and a starting signal is generated from the smoothing capacitor 4 at the gate of the sub-thyristor 20 by a delay integrating circuit 23 consisting of a resistor 21 and a capacitor 22. It has become. Note that the resistances indicated by reference numerals 24 and 25 are the gate termination resistances of the main thyristor 7 and the sub-thyristor 20, respectively.

This circuit operates as follows. Switch 2 to turn on the power
When started by turning on the AC power, the AC power is rectified by the rectifier diode bridge 3, and the charge is stored in the smoothing capacitor. The rush current (rush current) during this period is limited by the rush current limiting resistor 6. The resistance value of the inrush current limiting resistor 6 depends on the conditions of use, the capacity of the smoothing capacitor, etc., but a value of 4.7Ω is usually selected, for example. A delay integration circuit 23 consisting of a resistor 21 and a capacitor 22 connects the smoothing capacitor 4 with their time constants.
After being delayed for the time required to charge the secondary thyristor 2
A gate current is supplied to the gate of ゜, and the sub-thyristor 2
Turn on 0. At that time, smoothing capacitor 4
The anode current of the auxiliary thyristor 2o flows due to the voltage drop across the inrush current limiting resistor 6 caused by the small charging current and the current flowing through the load 5. As described above, since the cathode of the sub-thyristor 200 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 the anode current of the main thyristor, and both ends of the inrush current limiting resistor 60 become in the same state as if they were short-circuited.

As a result, the anode current of the sub-thyristor 20, that is, the gate current of the main thyristor 7, decreases, but 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. Once the power is turned on, the thyristor will automatically turn on and off again 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 thyristor's holding current), the thyristor turns off again, but
At this time, the self-current of the resistor 6 is small, and when the load shifts to heavy, a gate current sufficient to turn on the main thyristor 7 flows, and the main thyristor 7 is turned on again.

For example, in general, the gate current of the main thyristor 7 requires a power of about 35 to 36 mA; if a two-stage thyristor configuration as in this embodiment is used, the power of the auxiliary thyristor 20 is
A gate current of about 0.5 mA is sufficient. As mentioned above, since the gate current of the main thyristor 7 of about 35 mA is supplied by the voltage drop across the resistor 6, the current required to control this thyristor is essentially 0.5 mA.
This makes it possible to save power and to obtain a starting signal from the smoothing capacitor 4.

Although not shown, if a noise suppressor capacitor is inserted in parallel with the terminal resistor 24 of the gate of the main thyristor 7, the thyristor will turn due to thin pulse noise.
You can prevent it from turning on more completely. Further, 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 an amplifying element for driving the main thyristor 7, it is also possible to use a transistor 20' as shown in Fig. A.3. 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 made smaller, simpler, and less expensive. It has many excellent effects, such as being able to reliably control the gate of the thyristor without being affected by input voltage fluctuations or the temperature characteristics of the thyristor.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing the prior art, Figures E and 2 are circuit diagrams showing one embodiment of the present invention, and Figure 3 is a diagram illustrating the 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... Rush current limiting resistor, 7... Main thyristor, 20... Sub thyristor, 20'... Transistor, 23... Delay integration circuit.

Claims (1)

[Claims] 1. A circuit for controlling a short-circuit thyristor connected in parallel with an inrush current limiting resistor of a capacitor-input rectifier and smoothing circuit, comprising an amplifier element and an amplifying element connected between the gate and anode of the thyristor. and a delay integration circuit inserted into a rectifying and smoothing circuit to control the amplification element, the gate current of the thyristor is controlled through the amplification element by the voltage drop of the inrush current limiting resistor when the thyristor is not turned on. A thyristor control circuit for an inrush current limiting circuit, characterized in that the gate current is reduced after the thyristor is turned on. 2. Claim 2 in which the amplifying element is a thyristor.
The thyristor control circuit according to item 1.