JPS58215970A - Switching power source - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a switching power supply device, and in particular, two sets of switching elements operate simultaneously on and off to reduce the power consumption of one transformer.
In a switching power supply device that drives the next winding, even if one switching element fails due to a short circuit, the other switching element will not be damaged. (2) Prior art and problems For example, switching elements such as transistors Due to its high efficiency, switching power supply devices using the BACKGROUND ART are widely used as power sources for data processing equipment and various electronic devices.

A conventional switching power supply device has a configuration as shown in FIG. 1, for example. The transistors Q=, Q= as switching elements are controlled on and off simultaneously by the drive signal output from the drive circuit 1, and the drive signal of the drive circuit 1 is controlled by monitoring the output voltage of the capacitor 00. It is controlled by a control signal transmitted from circuit 2.

In FIG. 1, when transistors Ql and Q2 are turned on at the same time, power supply B-) transistor Q1-winding Wt-)
A square wave current flows through the transistor Q2-power supply E circuit.

As a result, a rectangular wave voltage is generated in the secondary winding of the transformer T, which is connected to the diode D.

It is rectified by D4, smoothed by inductance L and capacitor 0, and a DC output is obtained. and transistor Q1. When Q- is turned off, a back electromotive voltage of polarity ◯ and e as shown in the figure is generated in the 9th winding W1.

This back electromotive voltage is applied to the power source E by the circuit of (1) - diode DI - power source E - diode D coo e - winding W1 - (2), and the magnetic flux of the transformer T is reset.

By the way, for some reason, 1, for example, transistor Q=
When - is short-circuited, if transistor Q= is turned on, current will flow in the same circuit as when transistor Ql is turned on, but even if transistor Ql is turned off, the reverse 8 power of winding W+ Accordingly, ■-transistor Q
2-Diode D2-e-A current flows through the closed circuit of the winding Wt-■, the winding Wl becomes short-circuited, and the magnetic flux is not reset.

Therefore, when the transistor Q1 is turned on in the next cycle, the core of the transformer T is further excited in the same direction. As a result, the iron core of the transformer becomes saturated, and the output side of transistor Q1 also becomes short-circuited, causing a short-circuit current to flow through transistor Ql.
1 will also be destroyed. When the transistors Qt and Q* are short-circuited in this way, the output voltage of the power source E decreases.

If another device is connected to the power source E, the applied voltage may become small and have an adverse effect, or the short circuit may cause the power source E to overcurrent and be damaged.

(3) Purpose of the invention The present invention aims to improve these problems.

Transistor Ql or Q! An object of the present invention is to provide a switching power supply device that prevents a transformer from becoming saturated even if a short circuit occurs.

(4) Structure of the Invention In order to achieve this object, in the switching power supply device of the present invention, two switching elements simultaneously turn on and off to drive the primary winding of a transformer. The present invention is characterized in that a wire is provided and each of these separate windings is connected to a power source through a diode.

(5) Examples of the invention An embodiment of the present invention will be described based on FIG.

In the figure, the same reference numerals as in FIG. 1 indicate the same parts, and T-l;
A transformer used in the present invention, with a primary winding W
A reset winding Ws is provided outside the primary and secondary windings Wa,
W4 is provided. in this case.

When a positive voltage is applied to the primary winding W1 as shown in the figure and a current flows, each of the windings W, Wa, Wa is configured so that a positive voltage is generated as shown in the figure.

Transistors Q=, Q= are simultaneously controlled on and off by a drive circuit l. Therefore, transistor Ql
, When Q= is on, current flows through the primary winding W1,
As a result, a voltage is induced in each of the windings W2 to W4 so that a positive voltage is generated at the mark. At this time, the induced voltage in the secondary winding W2 is rectified by the diodes D3 and D4, smoothed by the inductance L and the capacitor O, and a DC voltage is output. Based on this output state, the control circuit 2 controls the drive circuit to control the transistors Ql and Q2.
It is possible to control the switching state of the DC output to a desired state.

For example, if a short circuit occurs in the transistor Q2, when the transistor Q1 is on, the current flows in the 11th order s-line W1 as before, and a normal voltage is also induced in the secondary winding.

Then when transistor Q1 turns off.

In the reset windings Ws and W4, back electromotive voltages of polarities shown by ■ and e in FIG. 2 are generated. Based on this ■s -
Dt -E -el and U $a -E -Ih -
A reverse voltage is applied to the power supply E by each circuit of e4.

As a result, the magnetic flux of the transformer T-1 is reset in the same manner as in the normal state. This magnetic flux reset state is the same even when the transistor Ql is short-circuited.

Therefore, in this power supply device, the transistor Qx.

If any of Q2 is short-circuited, the magnetic flux reset state of transformer T-1 remains unchanged from normal, so the iron core will not be saturated and the remaining transistors will not be damaged. Then, this damaged transistor can be detected by a separate appropriate means and replaced when the switching power supply is not in use. Note that the transistor Q1. Q2 and diode Di.

D2 needs to be at least twice the power supply voltage E.

Winding W1. The numbers of turns of Ws and Wa are equal.

(6) Effects of the Invention According to the present invention, even if either one of the transistors Q= or Q= is short-circuited, the magnetic flux reset state of the transistor remains unchanged from the normal state, so the iron core does not saturate. The remaining transistors will not be damaged. Therefore, even if one transistor fails due to a short circuit, the remaining transistors can perform a switching operation, and the reliability is doubled.

[Brief explanation of drawings]

FIG. 1 is a conventional switching power supply device, and FIG. 2 is a configuration diagram of an embodiment of the present invention. In the figure, 1 is a drive circuit, 2 is a control circuit, and Ql. Q= is a transistor, Di~D4 H diode, E
is the power supply, 0 is the capacitor, and L is the inductance. T and T-1 are transformers, Wt is a primary winding, WZ is a secondary winding Ws, and W4 is a reset winding. Patent applicant Fujitsu Ltd. Representative Patent Attorney Akira Yamatani

Claims (1)

[Claims] (1) In a switching power supply device in which two switching elements turn on and off simultaneously to drive the primary winding of a transformer, two separate windings are provided in the transformer, and each of these separate windings is connected to the power supply through a diode. A switching power supply device characterized by comprising: