| 摘要 |
PROBLEM TO BE SOLVED: To provide a step-up DC-DC converter capable of performing smooth start even when the stepped-up voltage is not yet generated, and capable of delaying battery consumption when the battery is used as an input power supply, suppressing an increase in consumption current. SOLUTION: The step-up DC-DC converter includes: a drive element (SW1) in which an inductor and a rectifying element are connected in series between a voltage input terminal and an output terminal and a current is allowed to flow through the inductor; and a control circuit (10) which generates a signal for controlling a driving element according to a feedback voltage from an output side and outputs the generated signal. In the step-up DC-DC converter, a power supply switching circuit (30) is provided which includes: a first diode (D2) with an anode terminal connected to the voltage input terminal, and a cathode terminal connected to a power supply voltage terminal of the control circuit; and a second diode (D3) with the anode terminal connected to the output terminal and the cathode terminal connected to the power supply voltage terminal of the control circuit, and is constituted so that a higher voltage out of an input voltage or an output voltage is supplied to the control circuit as a power supply voltage. COPYRIGHT: (C)2010,JPO&INPIT
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