| 摘要 |
PROBLEM TO BE SOLVED: To set a control signal to a high frequency for miniaturizing parts, without reducing the voltage conversion efficiency, and to minimize a circuit. SOLUTION: As a switching element for stepping-down/stepping-up, an NMOS transistor is used. When an input voltage is higher than a prescribed output voltage by the error signal of an error amplifier, a control signal is outputted from a PWM comparator 5, a drive signal is generated from a gate drive circuit 8, and an NMOS 10 for step-down is switched. At this time by the error signal whose level is shifted by a level shift circuit, the drive signal of a gate drive circuit 9 is set to a low level, and an NMOS 11 is turned off, thus lowering an output voltage Vout to a prescribed voltage. When an input voltage is lower than the prescribed output voltage by the error signal whose level is shifted by the level shift circuit, the control signal is outputted from a PWM comparator 6, and the NMOS 11 for step-up is switched. At this time, the NMOS 11 is turned on, thus raising the output voltage Vout until it reaches a prescribed voltage.
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