| 摘要 |
PURPOSE: A power supply unit capable of improving stability of an output voltage and responsiveness is provided to prevent overshoot by preventing consecutive turn-on state of a switch for synchronous rectification for a long time. CONSTITUTION: A power supply unit(1) includes a buck converter of a synchronous rectification mode, an error amplifier, a PWM signal generating circuit(5), a bypass switch(M3), and a mode control circuit(7). The buck converter includes a main switch device(M1), a switch device(M2) for synchronous rectification, a switching driving circuit(6), and an inductor(L1). The switch device for synchronous rectification alternately turns on/off with the main switch device. The switching driving circuit controls the switch device for synchronous rectification and the main switch device according to a switching control signal. The inductor is serially connected to a connection part of the main switch device and the switch device for synchronous rectification.
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