| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply circuit which operates at a high efficiency rate, without using complex means. SOLUTION: Serial circuits of switching elements Q1 and Q2 are connected to a dc supply E, and a high-frequency signal from a high-frequency oscillating circuit OSC is inputted to their control terminals. The output voltage of the circuit OSC is applied to a primary winding n1. Secondary windings n21 and n22 are connected so that connection polarities of the control terminal of the switching elements Q1 and Q2 become mutually reverse in polarities. A series circuit of a resonance circuit RS1 and a load circuit LD are connected in parallel with the switching element Q2, on the side of a negative pole of the dc supply E. A serial resonance circuit RS2 is connected to the secondary winding n21 in parallel, and a serial resonance circuit RS3 is connected to the secondary winding n22 in parallel. An output waveform of the circuit OSC is made substantially a sine wave, and the resonance frequencies of the serial resonance circuits RS2 and RS3 are set higher than the drive frequency of the circuit OSC.
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