Single phase single switch AC-AC voltage controller with improved input power factor

Abstract

High frequency switching power supplies have become part of electronic equipments to provide regulated DC of desired voltages at a lost 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 frequency because the regulating devices in their works as switches ensuring low device loss. Their output voltages 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 ĈUK converters. Researchers are trying to modify these DC regulators to regulate AC voltage. Utility AC voltage fluctuation both momentary and prolonged, affect adversely the domestic, industrial and commercial customers. A new topology of single phase Ĉuk AC voltage controller is proposed. The performance of the Ĉuk AC controller has good power factor and Total Harmonic Distortion (THD) values compared to the conventional AC-AC voltage controllers. Input AC current chopping by high frequency Ĉuk conversion for the positive and negative cycle provides low input current THD within IEEE 519, IEC 61000-3-2 standards and has improved power factor. The circuit efficiency is also acceptable for certain range of duty cycle. Positive and negative cycle Ĉuk conversion is performed by a single bi-directional switch and the output of two conversions is differentially connected to obtain the controllable step-up/step-down AC output voltage. The proposed circuit is investigated at low frequency switching so that it can be used in high power conversion also.