| 摘要 |
PROBLEM TO BE SOLVED: To enhance the efficiency of a switching power unit which has a power factor improving function. SOLUTION: The switching power unit has a rectifying circuit 4 connected to a pair of AC power terminals 1 and 2; first and second inductance windings L2 and L2 ; a transformer 5 having primary, secondary, tertiary, and quadratic windings N1 , N2 , N3 , and N4 ; a main switch Q1 ; an auxiliary switch Q2 ; and a capacitor Cq1 for soft switching. The first and second inductance windings L1 and L2 are magnetically coupled with each other, and they contribute to improvement of power factor and waveform. The auxiliary switch Q2 contributes to the formation of the discharge circuit of the capacitor Cq1 for soft switching. Discharging the capacitor Cq1 for soft switching before the ON control of the main switch Q1 reduces the switching loss.
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