| 摘要 |
PROBLEM TO BE SOLVED: To eliminate use of an auxiliary power circuit in a feedback control circuit by forming a feedback control circuit without any involvement of an insulation element. SOLUTION: When a switching device 2 which permits a commutation diode 6 to have continuity is off, induced electromotive voltage occurring in a main winding 22 becomes equal to output voltage Vo. In a voltage detection winding 23, voltage proportional to a turn ratio to that of the main winding 22 4s generated in a condition electrically insulated to the main winding 22. By using the voltage generated at the voltage detection winding 23, detected voltage dependent on fluctuations in the output voltage Vo can be supplied from an output voltage detection circuit 27 to a pulse duration control circuit 12, thereby attaining stabilizing the output voltage Vo without any involvement of an insulation element. By forming the output voltage detection circuit 27 as an auxiliary power supply for operating the pulse duration control circuit 12, the auxiliary power circuit can be eliminated.
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