| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem of a pseudo resonance type switching power supply of conventional frequency control method, wherein since a period in which until the accumulated energy of a transformer is emitted from a secondary winding at triggering of a power source is long, a switching frequency becomes lower down to audible range. SOLUTION: PWM control is employed during a soft start period at triggering, and it is switched to frequency control after completion of the soft start period, and the stress on a switching element is suppressed and audible oscillation frequency is eliminated, providing a switching power supply of high power conversion efficiency. COPYRIGHT: (C)2011,JPO&INPIT
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