| 摘要 |
PROBLEM TO BE SOLVED: To provide a resonance-type converter in which a switching loss is reduced by utilizing the fact that a voltage applied to a switching device is resonated by the output parasitic capacitance of the switching device and the inductance of a transformer and whose oscillation frequency is stable even if an input voltage or a load be fluctuated. SOLUTION: In a flyback-type converter, a DC voltage applied to a primary winding N1 is turned on/off by a switching device Q1 and a switching signal induced in a secondary winding N2 is rectified and smoothed to generate a main output voltage. Further, a zero-voltage detection unit 10 which outputs a trigger signal at the timing of the lowest value of a resonance voltage applied to the main switching device Q1, a mode switching unit 24 which outputs a mask signal which determines the minimum value of the resonance number and whose period isτ1 and a resonance number fluctuation width signal which determines a fluctuation width from the determined resonance number and whose period isτ2 alternately and an ON-period control unit 30 which makes the trigger signal valid while the mask signal is invalid and, after a lapse of the period while the mask signal is valid, turns on the main switching device when one of the timeup of the trigger signal and the timeup of the resonance number fluctuation becomes effective first are provided.
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