| 摘要 |
PROBLEM TO BE SOLVED: To enable cost-reduction and miniaturization of a switching power circuit. SOLUTION: A cross core driving transformer T1 is provided with a magnet MG to generate a steady magnetic fluxϕc2 in the opposite direction to a magnetic fluxϕc1 generated by a control current Ic flowing through a control winding Nc . As the result, in the state where the control current does not flow in the control winding not to generate the magnetic fluxϕc1 , the resonance impedance of the resonance type switching power circuit is kept high to protect parts such as a switching element, etc., from failure. This constitution eliminates the need to provide the power circuit whit a soft-start circuit and an overvoltage protection circuit, etc.
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