| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power-supply control circuit and its control method capable of widely improving the range of a temporal ratio in a PWM signal to be supplied, when an output voltage is adjusted by performing the adjustment of the temporal ratio to turn a main switch on and off under a PWM mode. SOLUTION: In the switching power-supply control circuit adjusts the output voltage under the PWM mode, by adjusting the temporal ratio in a main switching operation to turn the main switch in the switching power supply on and off by means of the PWM signal, a control circuit 430 has an error-amplifying circuit 432 to output an error signal, by comparing the output voltage with a reference voltage; and an on-time adjusting circuit 434 for starting generation of the PWM signal (VCONT) at each period, on the basis of a constant-period pulse(VPULSE), and to adjust the on-time in the PWM signal according to the output voltage of the error signal (VE). COPYRIGHT: (C)2009,JPO&INPIT
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