| 摘要 |
PROBLEM TO BE SOLVED: To reduce a margin for the design of a switching power supply and to facilitate its design and manufacture. SOLUTION: This switching power supply circuit has a composite resonance type switching converter having a self-exciting voltage resonance type converter as a basic structure. A drive winding and a tertially winding of a self-exciting oscillation circuit are magnetically coupled with each other by a drive transformer, and a series circuit comprising an inductor and a continuity control device Q2 is connected in parallel with the tertially winding N3. The current value of the series circuit is varied according to the variation of the level of a secondary DC voltage in order to control the oscillation frequency (switching frequency) of the self-exciting oscillation circuit to vary. With such a constitution, the constant voltage control can be realized by a composite control method, wherein a continuity angle and a switching frequency of a switching device are simultaneously varied, so that an orthogonal control transformer can be eliminated. |
