| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power supply device that performs power conversion with high efficiency and low loss irrespective of the size of a load.SOLUTION: A half bridge converter circuit 20 switches FETs 21, 22 to generate an output voltage Vo from an input voltage Vi, and a rear stage SW control circuit 40 controls on/off the FETs 21, 22 of the half bridge converter circuit 20 alternately with a dead time in between at a fixed on duty ratio and at a switching frequency depending on the size of a load. A step-up converter circuit 10 has an inductor L1, a smoothing capacitor C1 and a FET 11 for switching conduction to the inductor L1. A front stage SW control circuit 30 controls on/off the FET 11 of the step-up converter circuit 10 at a controlled on duty ratio to adjust the output voltage of the half bridge converter circuit 20. |
