| 摘要 |
PROBLEM TO BE SOLVED: To reduce a loss in a light load condition and recharge a bootstrap capacitor in a discontinuous conduction mode (DCM) in the light load condition.SOLUTION: A high side driver 2 and a low side driver 3 drive a high side switch Q1 and a low side switch Q2. A boot terminal BOOT of the high side driver 2 is connected to one end of a bootstrap capacitor C, and a switching node SW connected with both elements Q1, Q2 is connected to the other end of the capacitor C. When a reverse current detection circuit 5 connected to the low side element Q2 generates a reverse current detection signal of the detection of generation of a reverse current of an inductor current Iflowing through an inductor L, both drivers 2, 3 control both elements Q1, Q2 to an off state. When a voltage observed between the terminal BOOT and the node SW in the off period of both elements Q1, Q2 falls below a predetermined reference voltage Vref, a force-charging circuit 7 charges the capacitor C. |
