AC voltage regulation by C^uk switch mode power supply

Abstract

High frequency switching power supplies have become part of electronic equipments to provide regulated DC of desired voltages at a low cost and high efficiency. These power supplies have several advantages over their counterpart the linear power supplies. Main advantages are smaller compact size due to elimination of step down transformer and small filters due to high frequency operation. These power supplies have high efficiency because the regulating devices in them works as switches ensuring low device loss. Their output voltage can be controlled for a wide range of input voltage fluctuation by changing the duty cycle of the switching signals. Four common types of switch mode converters are used in DC to DC conversion. They are BUCK, BOOST, BUCK-BOOST and CI\UK converters. Researchers are trying to modifY these DC regulator to regulate AC voltages. Utility AC voltage fluctuation both momentary and prolonged, affect adversely the domestic, industrial and commercial customers. In this thesis an AC Cl\uk regulator made of. ideal switches and practical IGBT switches have investigated. For generation of switching voltage a commercially available IC chip SG l524B is used, thus circuit is compact and more viable. The same chip is utilized to regulate the output voltage by varying the gate signal voltage of the IGBTs if any changes occur in output voltage. As a result the regulator is maintaining constant voltage across the load during any change in supply voltage as well as for variation of load. Freewheeling path and surge voltage across switches create problem in the proposed regulator. Snubbers are used for suppressing surge voltage across switches. Input current of this regulator is greatly reduced to a acceptable limit but still efficiency of this regulator is very poor and needs further research to increase the efficiency to make the regulator commercially viable. In this thesis input filter capacitor of proper size is used for improving the power factor and which decreases the input current.