JP2002078330A - Switching power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the power consumption of a switching power supply, when its oscillation is stopped. SOLUTION: This switching power supply comprises a series circuit, which is composed of the primary winding 4 of a converter transformer 11, a switching device 5, a rectifying/smoothing circuit 17 connected to the auxiliary winding 9 of the converter transformer 11 and a primary control circuit 6 and are connected to a rectifying/smoothing circuit on the primary side of the converter transformer 11, a starting resistor 8 connected between the primary winding 4 and the primary control circuit 6, and a photocoupler I2 connected between the primary control circuit 6 and an external signal input terminal 16. The collector of a PNP transistor 7 is connected to the primary control circuit 6, the emitter of the transistor 7 is connected to the rectifying/smoothing circuit 17 of the auxiliary winding 9 and the starting resistor 8, and the base of the transistor 7 is connected to the collector of the transistor of the photocoupler 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply for reducing the power consumption of the switching power supply.

[0002]

2. Description of the Related Art A conventional switching power supply uses an on / off circuit built in a primary control circuit 6 as shown in FIG.
There are those directly connected, performs on / off control of the DC output voltage V _O. Because of the above configuration,
When the DC output voltage _{VO is} off, a current flows through the primary side control circuit 6 via the starting resistor 8 and power is consumed.

[0003]

Because of the above-mentioned problem, the circuit configuration for suppressing the current flowing to the primary side control circuit 6 via the starting resistor 8 when the DC output voltage _{VO is} stopped, thereby reducing the input power. Had been requested.

[0004]

According to the present invention, there is provided a rectifying / smoothing circuit on the primary side of a converter transformer 11, which comprises a primary winding 4, a switching element 5, A rectifying / smoothing circuit 17 connected to the winding 9;
A series circuit with the secondary control circuit 6 is connected, and the primary winding 4
In the switching power supply in which the starting resistor 8 is connected between the primary control circuit 6 and the primary control circuit 6 and the photocoupler 12 is connected between the primary control circuit 6 and the external signal input terminal 16, Connect the collector of PNP transistor 7,
A switching power supply characterized in that the emitter is connected to the rectifying / smoothing circuit 17 of the auxiliary winding 9 and the starting resistor 8 and the base is connected to the collector of the transistor of the photocoupler 12.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As in the switching power supply circuit of FIG. 1, a collector of a PNP transistor 7 is connected to a primary control circuit 6, and an emitter is connected to a rectifying / smoothing circuit 1 of an auxiliary winding 9.
7 and the starting resistor 8 and the base is the photocoupler 1
2 connected to the collector of the transistor. An external signal turns on / off a current flowing to the diode side of the photocoupler 12 and turns on / off the PNP transistor 7.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a basic circuit of an embodiment of the present invention,
FIG. 2 shows a conventional circuit. With the circuits of FIGS. 1 and 2,
When the change in power consumption [W] when the input voltage is increased from 83 V to 264 V while the output is stopped, the following Table 1 and FIG. 3 are obtained. 8, the current flowing to the primary control circuit IC6 is increased, whereas in the present embodiment, the current flowing to the primary control circuit is cut by the PNP transistor, so that the power consumption is reduced. You can see that there is.

[0007]

[Table 1]

[0008]

As described above, the PNP transistor 7 is connected to the primary control circuit 6, the rectifying / smoothing circuit 17 of the auxiliary winding 9, the starting resistor 8, and the transistor of the photocoupler 12, and the transistor 7 is turned on. By performing the / off operation, the current flowing from the starting resistor 8 to the primary side control circuit 6 when the DC output voltage _{VO is} stopped is suppressed, so that the power consumed by the primary control circuit 6 is greatly reduced in the embodiment. I was able to.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a switching power supply according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a conventional switching power supply.

FIG. 3 is a graph showing input voltage-power consumption characteristics when output voltage is stopped.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC power supply 2 Full-wave rectifier circuit 3 Smoothing capacitor (polarity) 4 Primary winding of converter transformer 5 Switching element 6 Primary control circuit 7 PNP transistor 8 Starting resistance 9 Auxiliary winding 10 Secondary winding 11 Converter transformer 12 Photocoupler 14 Secondary-side rectification / smoothing circuit 15 Load 16 External signal input terminal 17 Rectification / smoothing circuit for auxiliary winding

Claims (1)

[Claims] 1. A series circuit of a primary winding, a switching element, a rectifying / smoothing circuit connected to an auxiliary winding, and a primary control circuit is connected to a rectifying / smoothing circuit on a primary side of a converter transformer. A switching power supply comprising: a starting resistor connected between the primary winding and the primary control circuit; and a photocoupler connected between the primary control circuit and the external signal input terminal. A switching power supply having a collector connected to a PNP transistor, an emitter connected to a rectifying / smoothing circuit and a starting resistor of an auxiliary winding, and a base connected to a collector of a transistor of a photocoupler.