| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that a delay occurs until an output voltage becomes stable when returning to a normal load from a light load. SOLUTION: A switching circuit 12 includes a switching transistor M1 and a synchronous rectifying transistor M2 connected in series between an input terminal 102 and ground, and a voltage at a connection point between two transistors is applied to one end of an inductor L1 as a switching voltage Vsw. In a pulse modulator 20, a PWM signal Spwm is generated of which duty ratio is adjusted so that the output voltage (Vout 2) of a step-down type switching regulator 200 approximates a predetermined reference voltage Vref. In a return pulse signal generating part 30, a return pulse signal S1 is generated of which the duty ratio is set without correlating with the output voltage of the step-down type switching regulator 200. In a driver circuit 10, a switching circuit 12 is driven by selecting either one of the PWM signal Spwm or the return pulse signal S1. COPYRIGHT: (C)2008,JPO&INPIT
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