Comparison between peak and average current mode control of improved bridgeless flyback rectifier with bidirectional switch

Abstract

This paper compares peak and average current mode control of flyback rectifier with bidirectional switch. The control schemes employs an outer voltage feedback loop, which maintains the output voltage as constant and an inner loop, which sense the input current. Average and peak current mode control of flyback rectifier is suitable for obtaining a regulated output voltage with a varying input. Voltage equivalent of input current is averaged by using high gain current error amplifier, which again compared with the reference voltage in the case of average current mode control. But in the case of peak current mode control, peak inductor current has been sensed and this gives rise to many serious problems, including poor noise immunity, a need for slope compensation, and peak-to-average current errors which the inherently low current loop gain cannot correct. Reference voltage is produced by multiplying the rectified input voltage with the error output voltage. These control methods obtain better line and load regulation with the addition of inner current loop compared with voltage mode control. Also the rectified input voltage feedback achieves better input power factor. Conventional flyback rectifier is the inter connection of a diode bridge rectifier in the input side and a flyback converter. In order to obtain a highly efficient flyback rectifier with fewer losses an improved flyback rectifier is introduced. Improved bridgeless flyback rectifier only introduces a switch with common gate drive, a diode and an additional winding in the secondary side. Thus the weight of the converter is not affected with these additional components. Proposed peak and average current mode control can be used as an adapter. Design details of average current mode control also discussed and simulation and hardware results are presented.