| 摘要 |
PROBLEM TO BE SOLVED: To prevent a continuance of a self-oscillation generated when a main switching element is turned off in a state where there is a voltage in a high-voltage side output terminal.SOLUTION: A switching power supply comprising a rectifier circuit of a synchronous rectification type, includes: a rectification switch Q3 that is serially connected to a secondary main winding Ns1 of a main transformer T1 and turns-on in synchronization with ON of the main switch Q1; and a translocation switch Q4 that is connected to the secondary main winding Ns1 in parallel and turns-o in synchronization with OFF of the main switch Q1. The switching power supply further comprises: rectification elements CR1 and CR2, and transistors Q5 and Q6 that construct an auxiliary switch circuit turning-off the translocation switch Q4 for preventing a continuance of self-oscillation when the stop of the main switch Q1 in a state where there is a voltage Vout is in a high-voltage side output terminal +Vout.SELECTED DRAWING: Figure 4 |
