Murata Manufacturing Co., Ltd.

Soichi Watanabe

Koji Nishi

Takashi Kurokawa

Masato Fujino

In a power supply apparatus in which a source of a MOSFET is connected to a node of a rectifier diode and a choke coil through a resonance coil, a series circuit including a capacitor and a MOSFET is connected to a series circuit including the resonance coil and the rectifier diode, and the MOSFET and the MOSFET are driven by PWM control so that the MOSFET and the MOSFET are alternately turned on with a period in which both MOSFETs are turned off, a resistor is connected in parallel with the capacitor, and optionally another diode is connected in series with the resistor.

Power supply apparatus

In a power supply apparatus, in a standby mode, control signals for controlling a first MOSFET of a power supply apparatus to be turned on and a second MOSFET to be turned off are supplied to the gates of the first and second MOSFETs from a control circuit, respectively. The emitter of a PNP transistor is connected to the gate of the second MOSFET through a diode of a switch circuit and the collector is connected to the ground. A power supply operation control signal is input to the base of the PNP transistor. When a power supply operation control signal in a Low state is input to the base in a standby mode, the emitter and the collector are connected to each other. Accordingly, the gate of the second MOSFET has a potential substantially the same as a ground potential and the second MOSFET is turned off irrespective of the control signal.

A DC-DC converter includes first and second MOSFETs. The source of the first MOSFET is connected to the node between a rectifier diode and a choke coil through a resonance coil. A series circuit including the resonance coil and the rectifier diode is connected in parallel to a series circuit including a capacitor and the second MOSFET. A diode and another capacitor are connected in parallel across the drain and source of the second MOSFET. Another diode is connected in parallel to a series circuit including the first MOSFET and the resonance coil. A control circuit is provided between an output terminal and the gates of the first and second MOSFETs so as to perform PWM control so that the first and second MOSFETs are alternately turned ON, with a period when both MOSFETs are OFF being provided between the ON periods.

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Nagaokakyo, Japan

Soichi Watanabe