| 摘要 |
PROBLEM TO BE SOLVED: To reduce the margin in design for the facilitating designing and manufacturing, and to enhance power conversion efficiency. SOLUTION: A complex resonance switching converter, provided with a self-exciting, voltage-resonant converter, is taken as a basic component, and the drive winding of a self-exciting, oscillation drive circuit and a tertiary winding N3 are magnetically coupled with each other by a drive transformer. A variable impedance parallel-resonant circuit is composed of the tertiary winding N3, a capacitor Cc, and an impedance control element Q2. The impedance of the parallel-resonance circuit is varied in correspondence with fluctuation in the level of secondary-side, direct-current output voltage. Thus, the oscillation frequency (switching frequency) of the self-exciting, oscillation drive circuit is controlled variably, to effect constant-voltage control. As a result, an orthogonal control transformer can be omitted. Furthermore, for the drive transformer CDT, a closed magnetic circuit core of an amorphous magnetic material is selected, so that the level of reverse current is higher than the level of forward current, with respect to the base current of a switching element Q1.
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