| 摘要 |
PROBLEM TO BE SOLVED: To avoid the concurrent turning-on of a main switching device Q1 and a synchronous detection switching device Q2 of a flyback type switching power supply. SOLUTION: The main switching device Q1 is connected to a primary winding LP of a transformer T1 which operates as an energy storage inductance element to repeat turning on and off. In a secondary winding LS, the synchronous detection switching device Q2 is connected between loads, and a series circuit 26 is connected in parallel. The series circuit 26 includes a synchronous detection inductance element L1 and a diode D1. In an off-period Toff of the main switching device Q1, the synchronous detection inductance element L1 completes the discharging of storage electric power by the operation of the diode D1 at a time t3 earlier than a time t6 when the storage electric power of the transformer T1 completes the discharging. This is detected by a diode D2 for voltage detection to apply a control signal which turns off the synchronous detection switching device Q2. COPYRIGHT: (C)2004,JPO
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