A pulse-width-modulated controlled-transformer post regulator

The theory of operation of a controlled transformer is described. A PWM controlled transformer is proposed and implemented in a forward converter to provide post regulation. Experimental results are presented to verify the new control scheme. Overall efficiency of 82%-86% is achieved in a 200khz, 500-watt, 5V-output off-line regulator. A discussion of design issues of the controlled transformer is also presented.