DESIGN AND IMPLEMENTATION OF SINGLE STAGE INTEGRATED BUCK-FLYBACK CONVERTER BASED POWER SUPPLY

This paper investigates the integrated buck- flyback converter as a good solution for implementing low- cost high-power-factor ac-dc converters with fast output regulation. It will be shown that, when both buck and flyback semistages are operated in discontinuous conduction mode, the voltage across the bulk capacitor, which is used to store energy at low frequency, is independent of the output power. This makes it possible to maintain the bulk capacitor voltage at a low value within the whole line voltage range. This project implements a buck converter for the first stage and flyback converter for output stage. These topologies are very good solution for fast output dynamics. Another advantage of this integrated buck-flyback converter, is that switch handles the highest of buck or flyback current not addition of both currents. The remaining current is handled by the diodes of the integrated switch, which gives lower losses. The buck capacitor voltage is independent of load, duty cycle, and switching frequency and it only depends on the ac input voltage and the ratio of the two buck and flyback inductance. This is an important feature of the integrated converter operating in discontinuous mode, which allows them to provide fast output voltage regulation. The simulation has been performed to verify the feasibility of the proposed LED lamp driver.