| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply apparatus capable of reducing the cost. SOLUTION: The power supply apparatus is provided with a timer circuit 6 for outputting a high level signal when turning on power is detected based on a terminal voltage of a capacitor C10 and outputting a low level signal after the predetermined elapsed time and a logical sum circuit OR1 inserted between a MOSFET gate comprising a switching element Q2 and a PWM control circuit 3 as a signal generating means. The logical sum circuit OR1 inputs an output signal from the timer circuit 6 and an output signal from the PWM controlling circuit 3. While the output signal from the timer circuit 6 is high, the PWM control circuit 3 does not output a PWM signal. When the output signal from the timer circuit 6 is low, the PWM controlling circuit 3 begins to output the PWM signal. After power is turned on, a bootstrap capacitor Cs is charged by the capacitor C10 as a control power supply through a path made of an inductor L1 and the switching element Q2 of a step-up and step-down chopper circuit 1.
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