Pulse width modulation bias to minimize effect of noise due to ramp switching

摘要

A control system using pulse width modulation, current-mode control to regulate a flyback converter for small input currents. The control system generates a ramp voltage indicative of an input current of the converter with an added bias to overcome the effects of switching noise attributable to parasitic elements in the converter. The ramp voltage is compared with an error voltage is order to obtain the pulse width modulated on-time of a primary switch. Thus, the control system maintains control for small duty cycles of the primary switch by having a control region immune to switching noise.