Switch supply source

Abstract

A switching power supply which can prevent the output voltage Vout from fluctuating or undershooting when the instruction for stopping the operation is issued is disclosed. A switching power supply according to the present invention employs a transformer having a primary coil and a secondary coil, a switching circuit connected between an input terminal and the primary coil of the transformer, a rectifier connected to the secondary coil of the transformer, a smoothing circuit located at a subsequent stage of the rectifier and including an output capacitor, a control circuit controlling the switching circuit, and an operating voltage generating circuit, responsive to an instruction for stopping a switching operation, for supplying an operating voltage to the control circuit using at least energy stored in the output capacitor. Thus, the switching power supply of the present invention can substantially linearly lower the output voltage Vout.

Description

technical field [0001] The present invention relates to a switching power supply, and more particularly, to a switching power supply capable of preventing undershoot and fluctuation of an output voltage Vout when the operation of the switching power supply is stopped. Background technique [0002] Switching power supplies are widely used as power supplies for electronic and electrical equipment such as computers. [0003] Accompanying drawing 7 shows the circuit diagram of conventional switching power supply. [0004] As shown in FIG. 7, a conventional switching power supply consists of a transformer T1, a switching circuit on the primary side of the transformer T1, and a self-driven rectifier and filter circuit on the secondary side of the transformer T1. The switching power supply reduces a DC (direct current) input voltage in a voltage Vin supplied to a switching circuit on a primary side to generate a DC output voltage Vout and supplies it to a load. In FIG. 7, the loa...

AI Technical Summary

Problems solved by technology

[0030] As explained above, the conventional switching power supply has two main problems: one problem is that the output voltage Vout gradually decreases while fluctuating over a very long cycle time when an instruction to stop the operation of the switching power supply is issued; Undershoot occurs in the output voltage Vout when an instruction to stop the operation of the switching power supply is issued

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