Design and Development of SMPS with Synchronous Rectification Technique

Abstract

In SMPS there are different topologies like buck converter boost converter, flyback converter, push pull converter, half bridge converter, full bridge converter commonly used. SMPS works on high operating frequency which gives efficient output. The main reason which makes the SMPS most reliable power supply is that it is a compact size device. Using ferrite core for transformer we can reduce the size further making it useful for robotics and highly sophisticated applications. The drawback is production of electromagnetic interference and poor regulation. Also for simple circuit the power losses are more. In rectification side schottky diodes are used. The major factor, limiting the efficiency is the power loss in the schottky diode rectification. In most of topologies the synchronous rectification should never be allowed to turn on simultaneously, so short circuit condition can be created. These entire problems overcome by synchronous rectifier using MOSFETs. MOSFET is used for switching purpose which replace the schottky diode because of the better control can be achieved and so conduction losses can be reduced. In this project the technique called Synchronous rectification is used having the advantages of high performance, high power converters including better efficiency, low power dissipation, better thermal performance, good quality, improved manufacturing yields through automated assembly processes (higher reliability). This is achieved by two different control methods i.e. Voltage mode control and Current mode control.Topology is selected depending on the ratings of proposed load. In this project Half- bridge topology is best suited for the 25 V dc, 250 Watt. ii