Power-Factor Correction for AC-DC Converter

Abstract

The conversion of A.C into D.C determines the distortion of the mains current A.C., which degrades the input power factor. The main reason for a poor power factor is the non-linear nature of the circuit. The power factor is improved by using a basic boost converter and a control technique based on the fixed off time (FOT) approach .The traditional approach to the correction of the power factor in the boost converter is the continuous conduction mode with fixed frequency (FF-CCM) and the transition mode (TM) PWM (fixed connection time, variable frequency). In the first mode, the inductor operates in continuous conduction mode (CCM) and uses the average current-mode control mode, a complex technique involves a considerable quantity of components. The second method uses the more complex control technique of the peak current mode that makes the inductor work between continuous and discontinuous mode, which uses fewer components, unstable greater than 50% duty cycle and is more cost efficient .A third approach, the fixed off time (FOT) is gaining popularity which is conditionally stable for a duty cycle of over 50% and does not need compensation. The dissertation involves the work carried out to use the power factor correction (PFC) based with the DC-DC Flyback converter. To verify the design and operation of the circuit, the simulation is performed in PSIM. Finally, to illustrate the implementation of the proposed technique, a 24 volt battery charging circuit is selected. The CCCV charging mode is also explained using the look up table concept.