JPH0360876U - - Google Patents

Description

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram of a conventional configuration, FIG. 3A is a time chart showing waveforms in FIG.
Figures B and C are time charts showing the waveforms in Figure 2. DESCRIPTION OF SYMBOLS 10... Transformer, 11... Primary winding, 12... Secondary winding, 20, 52... Transistor, 30... Rectifier circuit, 40... Current control circuit, 50, 90... Current detection circuit, 51, 53, 54, 91... resistance.

Claims (1)

[Claims for Utility Model Registration] (1) A switching transistor that generates a pulsed drain current by applying a predetermined gate voltage to its gate terminal in a pulsed manner, and a primary winding connected in series to the drain terminal of this transistor. a rectifying circuit that rectifies the voltage generated in the secondary winding of the transformer and outputs a DC load voltage, and is connected in parallel to the series circuit formed by the primary winding and the drain-source terminal. When the load voltage is input and the load voltage deviates from a predetermined value, the application timing of the gate voltage is changed to bring the load voltage to a predetermined value, and when overcurrent detection information is received, the transistor is cut off. a current control circuit that disconnects the drain current of the transistor by connecting the current control circuit to the primary winding on the power input terminal side to measure the drain current flowing into the drain terminal of the transistor, and when the drain current exceeds a predetermined value, A switching power supply circuit comprising: a current detection circuit that inputs the overcurrent detection information to a current control circuit. (2) The current detection circuit includes a resistor directly connected between one of the power input terminals and the primary winding;
A transistor that turns on in response to the potential difference between both terminals of this resistor, and a voltage dividing resistor that divides the voltage between the power supply input terminals by the on operation of this transistor and inputs it to the current control circuit as the overcurrent detection information. 2. The switching power supply circuit according to claim 1, further comprising a switching power supply circuit according to claim 1.