| 摘要 |
<P>PROBLEM TO BE SOLVED: To obtain a power supply circuit having a power factor improving function in which power conversion efficiency is enhanced while decreasing the number of circuit components, and to put a voltage resonance converter equipped with a secondary series resonance circuit to practical use. <P>SOLUTION: In the switching power supply circuit, a power isolation transformer PIT has a coupling fact k=0.7 or less and abnormal operation where a current flows into a switching element at a timing before ending off period of the switching element is eliminated in case of middle load. A power factor improving circuit 10 makes a switching output (resonance pulse voltage) obtained in the primary winding N1 of the power isolation transformer PIT induce in a tertiary winding N3, and voltage feedback to a rectification current passage is effected through electrostatic coupling of a feedback capacitor C20. A switching diode D1 chops a rectifier current depending on the feedback voltage. <P>COPYRIGHT: (C)2007,JPO&INPIT |
