| 摘要 |
PROBLEM TO BE SOLVED: To facilitate the design and manufacture and improve the power conversion efficiency. SOLUTION: With a composite resonance type switching converter equipped with a self-excited voltage resonance type converter as basic constitution, detection winding NA, drive winding NB for a self-excited drive circuit, and control winding Nc are wound on a drive transformer CDT. The control winding Nc and the drive winding NB are magnetically coupled with each other. Besides, this switching power circuit is provided with a circuit where the control winding Nc and the conduction control element Q2 are connected in series. As regards stabilization, the switching frequency is variably controlled by varying the level of a base current flowing to the base of the switching element Q1 from a self-excited oscillation drive circuit by varying the quantity of current conduction of the conduction control element Q2. Consequently, an orthogonal control transformer is omitted. Moreover, the switching loss of the switching element Q1 is reduced by so arranging the voltage between the base and the emitter of the conduction control element Q2 as to be saw-toothed waves.
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