JPH03871Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a switching regulator, and particularly to a switching regulator that can prevent destruction of switching transistors due to rush current generated at startup.

Conventional technology In general, a switching regulator has a capacitor input type rectifying and smoothing circuit consisting of a rectifying circuit and a capacitor on the input side, and connects the primary winding of the output transformer and the DC line of the rectifying and smoothing circuit. A switching transistor is connected in series, and the switching transistor is turned on and off to supply direct current to a load connected to the secondary winding of the output transformer. However, in this switching regulator, if the load is a lamp load or a load including a capacitor, a rush current flows through the switching transistor at startup, which may destroy the switching transistor.

The problem that the invention aims to solve: In order to prevent such destruction of switching transistors, conventional methods apply pulses whose pulse width gradually increases to the base of the switching transistor to gradually increase the conduction time of the switching transistor. method has been adopted. Although this method can also prevent destruction of the switching transistor due to inrush current, it takes time until steady current is supplied to the load, and the above method can be used to rapidly widen the pulse width to supply steady current to the load. If the time until the switching transistor is shortened, the switching transistor may exceed its safe operating range and be destroyed.

Summary of the invention This invention provides a parallel circuit consisting of a resistor and a thyristor in the DC line between the capacitor of the rectifying and smoothing circuit on the input side and the switching transistor, and also connects the thyristor with a gate after a predetermined time after the switching transistor is activated. By connecting a delay circuit that provides a signal between the winding provided in the drive transformer and the gate of the thyristor, the above drawbacks are resolved, and when supplying power to loads including lamp loads and capacitors. To provide a switching regulator that does not destroy a switching transistor and can shorten the time until a steady current is supplied to a load.

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 shows a separately excited type switching regulator, in which an input smoothing capacitor 2 is connected between the DC lines of a full-wave rectifier circuit 1, and a primary winding 7 of an output transformer 6 is connected to both ends of the capacitor 2. A parallel circuit including a switching transistor 3, a resistor 4, and a triac (bidirectional three-terminal thyristor) 5 are connected in series. A rectifying and smoothing circuit 9 consisting of a diode 10 and a capacitor 11 is connected to a secondary winding 8 provided in the output transformer 6, and a load 12 is connected to an output terminal of the rectifying and smoothing circuit 9. Also, in order to drive the transistor 3, a drive transformer 13 is provided.
and a control circuit 17 connected to both ends of the load 12. The drive transformer 13 has a primary winding 14 connected to a control circuit 17.
, a secondary winding 15 connected between the base and emitter of the transistor 3, and a tertiary winding 16 connected to a delay circuit 19 via a diode 18. The control circuit 17 includes a pulse width modulation circuit, and outputs a drive pulse according to the output voltage. The delay circuit 19 includes an integrating circuit consisting of a resistor 22 and a capacitor 23, and a constant voltage diode 2 that becomes conductive when the capacitor 23 is charged to a predetermined level.
4, and a noise removal circuit consisting of a capacitor 25 and a resistor 26. Both ends of the capacitor 25 and the resistor 26 are connected between the main electrode _T1 and the gate G of the triac 5. Also, try 5
The main electrode T ₂ of is connected to a resistor 4, a capacitor 2 and a full-wave rectifier circuit.

In the above circuit, when an AC power source (not shown) is applied to the full-wave rectifier circuit 1, the AC voltage is rectified by the full-wave rectifier circuit 1 and charges the smoothing capacitor 2. When capacitor 2 is charged, control circuit 1
A drive pulse as shown in FIG. 2A is applied from 7 to the primary winding 14 of the drive transformer 13, and a voltage in the direction shown by the arrow 40 is induced in the secondary winding 15. Therefore, transistor 3 is turned on and 1
A current flows through the secondary winding 7 and the resistor 4, and a voltage corresponding to the winding is induced in the secondary winding 8. This voltage is in a reverse bias direction, indicated at 43, with respect to diode 10.

Next, when the drive pulse is no longer applied from the control circuit 17 to the primary winding 14, no voltage is induced in the secondary winding 15, and the transistor 3 is turned off. As a result, a voltage is generated in the secondary winding 8 that turns on the diode 10, and the transistor 3
The energy stored in the output transformer 6 during the period when the output transformer 6 is on is released to the load via the rectifying and smoothing circuit 9. When the release of the energy stored in the output transformer 6 is completed, the drive pulse of the control circuit 17 Then, transistor 3 is turned on again, and the same operation is repeated. On the other hand, the voltage induced in the tertiary winding 16 during the off-period of the transistor 3 is not immediately applied to the gate of the triac 5, and is applied to the diode 18.
The capacitor 23 is charged through the resistor 22. When the combined charging voltage of the capacitor 23 reaches a voltage that exceeds the level of the voltage regulator diode 24, a gate signal is generated at a time point _t1 as shown in FIG. That is, the triac 5 is driven with a predetermined time delay after the transistor 3 is activated. This delay time is set to be the shortest time without destroying the transistor 3 when the triac 5 is turned on. Therefore, when the triac 5 is turned on, a limited current is already being supplied to the load 12, so that no excessive current flows through the transistor 3.

As described above, in the circuit of the present invention, current flows through the transistor 3 via the resistor 4 at startup, and a limited current is supplied to the load. Furthermore, after a predetermined period of time, the resistor 4 is shortened by the triax 5 and a steady current is supplied to the load, which prevents destruction of the transistor 3 due to rush current and shortens the time until the steady current is supplied to the load. Can be done.

The present invention is not limited to the above embodiments, but can be further modified. In the above embodiment, a flyback type regulator is shown that supplies the energy stored in the output transformer 6 to the load 12 when the transistor 3 is off, but a forward type regulator that supplies energy to the load when the transistor 3 is on is shown. can also be applied. In addition, the parallel circuit consisting of the resistor 4 and the triax 5 is connected to the transistor 3
It can also be provided in a line connecting the collector of the input capacitor 2 and the input capacitor 2. Further, the triax 5 may be composed of one reverse blocking three-terminal thyristor connected in antiparallel. Furthermore, the delay circuit 21 can be modified in various ways.

Effects of the invention This invention provides a parallel circuit consisting of a resistor and a thyristor in the connection line between the capacitor and the switching transistor of the input side rectifying and smoothing circuit, and also connects a delay circuit between the winding provided on the drive transformer and the thyristor. Since it is connected between the gate and the switching transistor, it has the advantage of preventing destruction of the switching transistor at startup and shortening the time until steady current is supplied to the load.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a separately excited switching regulator showing an embodiment of the present invention, and FIG. 2 is a time chart showing the relationship between the drive signal of the switching transistor and the operation of the triac. 1...Full wave rectifier circuit, 2...Capacitor, 4...
...Resistor, 3...Switching transistor, 5...
...thyristor, 6...output transformer, 7...primary winding, 8...secondary winding, 12...load, 13...drive transformer, 16...tertiary winding, 19...delay Circuit, 34...drive circuit, G...gate.

Claims (1)

[Scope of utility model registration request] The primary winding of an output transformer and a switching transistor are connected in series between the DC lines of a capacitor-input type rectifying and smoothing circuit consisting of a rectifying circuit and a capacitor, and a switching transistor is connected in series based on the output of a driving circuit having a driving transformer. The capacitor and the switching transistor are connected to each other in the switching regulator, which supplies the output converted into DC from the secondary winding of the output transformer to the load by turning on and off the switching transistor. A parallel circuit of a resistor and a thyristor is provided on the line to be connected, and a delay circuit is provided to apply a gate signal to the thyristor after a predetermined time after the switching transistor is activated. A switching regulator characterized in that it is connected between a gate and a gate.