| 摘要 |
PROBLEM TO BE SOLVED: To reduce current consumption in a switching transistor and increase the efficiency of a power supply at light load. SOLUTION: This DC-DC converter 10 is provided with a load current detector 12 for detecting whether load current consumed by a load is large or small, an error detector and amplifier 11 for detecting the deviation of the output DC voltage at the load output side from a target voltage value, a controller 18 for generating a load control signal for pulse width modulation control of a switching transistor based on a signal from the error detector and amplifier 11, and a gate size changer 16 which selects a switching transistor which should be activated among a plurality of switching transistors M2, M3 based on a detection signal indicating whether the load is light or heavy and then supplies a load control signal to the activatd switching transistor.
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