Design and Simulation of Novel Single-Input Sampling Instance Control Circuit

This paper proposes a novel single-input sampling instance control circuit used in primary-side controller of Switch Mode Power Supplies (SMPS) without optical-coupler and secondary feedback control circuit. The novel control circuit is based on the idea determining the sampling instance of current switching cycle by the duration of the voltage pulse at the auxiliary wingding during the previous switching cycle. So the sampling instance is always kept constant, as long as the duration of the voltage pulse is not changed. The control deviations resulting from changeful parameters can be reduced. Thus, high controlling accuracy can be achieved. According to the design, the width of the sampling signal is adjustable, which enlarges the range of application. Besides, the characteristic of single-input makes the obtaining of input signal easy.