| 摘要 |
PROBLEM TO BE SOLVED: To realize high efficiency and suppress noise. SOLUTION: A transformer 1 is provided with tertiary winding n3. An output voltage control circuit 12 supplies the excitation energy of a transformer 12 to load R from tertiary winding n3, by turning on a switch Q2, based on the output voltage, during a period when a switch Q1 is off. When the switch Q2 is turned off, a leakage inductance L1, the excitation inductance of the transformer 1, and a capacitor C1 cause voltage resonance. The interval between the primary side and the secondary side of the transformer can be widened by positively making use of the leakage inductance L1, and the capacity to cause noise occurrence can be lowered. Moreover, the output voltage can be controlled by controlling the on-time of the switch Q2.
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