| 摘要 |
PROBLEM TO BE SOLVED: To enable switching operation even when an input voltage is reduced without reducing a degree of freedom in setting an output voltage.SOLUTION: An error amplifier OP1 outputs an error signal Sa in which an error of a detection voltage Vd1 of an output voltage Vo with respect to a reference voltage Vr1 is amplified. A comparator CP2 outputs a duty signal Sd having a duty according to the comparison result of the error signal Sa and a triangle-wave signal Sc. A driving circuit 2 outputs an on/off driving voltage to a gate of a transistor T1 on the basis of the duty signal Sd. A bootstrap circuit 4 steps up the on-driving voltage to a voltage higher than an input voltage Vi by performing charging to a capacitor C2 in an output-off period and by supplying a terminal voltage of the capacitor 2 to the driving circuit 2 in an output-on period. A frequency setting section 13 switches the frequency of the triangle-wave signal Sc generated by a triangle-wave generating section 12 in two stages according to an output signal Sb of a comparator CP1 that is a detection value of the error signal Sa. |
