| 摘要 |
In a power supply device, a synchronous rectifier step-down converter alternately turns on and off a switch and a synchronous rectifier switch. A reference voltage generator generates a predetermined reference voltage. An error amplifier outputs an error voltage such that an output voltage of the step-down converter approaches the predetermined reference voltage. A pulse-width signal generator generates a pulse-width signal controlling turning on and off the switch and the synchronous rectifier switch based on the error voltage. A driver circuit controls turning on and off the switch and the synchronous rectifier switch based on the pulse-width signal. An inductor is connected in series with output of the step-down converter. A bypass switch short-circuits an output terminal of the step-down converter to an input terminal of the step-down converter. A mode controller controls turning on and off the bypass switch.
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