An adjustable linear power supply with a phase-shift PWM tracking pre-regulator

An adjustable linear DC power supply using a switching-type tracking pre-regulator is described in this paper. To improve circuit efficiency, a full-bridge phase-shift pulse-width-modulation (FBPS-PWM) converter is employed to pre-regulate the input voltage of the adjustable power supply. In the proposed circuit scheme, there are two control loops. One is the linear regulator loop and the other is the FBPS-PWM converter loop. While the linear regulator loop regulates the output, the converter loop tracks the voltage variation. The output voltage of the tracking FBPS PWM converter is always greater than the output voltage of the adjustable linear regulator 2.5 volts. To verify the proposed scheme, a one-kilowatt 0∼60 volts/20 amperes prototype circuit is built. Simulation and experimental results show that the proposed hybrid scheme can obtain the merits of high efficiency and low output ripple.