Average current mode control of improved bridgeless flyback rectifier with bidirectional switch

Abstract

This paper introduces average current mode control of flyback rectifier with bidirectional switch. The proposed control scheme employs an outer voltage feedback loop, which maintains the output voltage as constant and an inner loop, which sense the input current. Average 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. Reference voltage is produced by multiplying the rectified input voltage with the error output voltage. Gating pulse is generated by using this signal. This control method 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. Here, two switches are connected in back to back to establish the bidirectional switch element, which will conduct both in the positive and negative half cycle of the ac input voltage. The transformer with dual output windings with a diode in each winding reduces the current stress across each diode. New topology adds an extra switch in the primary side and a diode in the secondary side. 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 average current mode control can be used as an adapter. Design and simulated waveforms are added in this paper for an output rating of 20V/1.5A.