Bridgeless Power Factor Correction with Integration of Forward and Buck-Boost Converters

Abstract

This thesis proposes a bridgeless power factor correction with integration of forward and buck-boost converters The rectifier can be considered equivalent to a single switch that controls two subconverters (buck-boost and forward subconverters) that share and deliver the total output power synchronously By using a high power factor for the buck-boost subconverter and an appropriate transformer design for the forward subconverter the total harmonic distortion (THD) of the input current can be effectively reduced To reduce the volume and core loss of the transformers the forward subconverter directly delivers a major part of the output power to the load Since no full-bridge rectifier or coupling capacitor is used in the current flowing path in the power conversion process (similar to the C?k converter single-ended primary inductor converter and Zeta converter) conduction losses are reduced and the efficiency and thermal performance of the proposed rectifier are enhanced Moreover because the proposed rectifier is designed to operate in the discontinuous inductor current mode the current loop is not required Furthermore the two switches in the circuit can be controlled using a single control signal which simplifies the design of the control system considerably The operating principles steady-state analysis and design guidelines of the proposed rectifier are detailed in this thesis To verify the effectiveness and feasibility of the proposed rectifier simulations and experiments are conducted using a 135 W prototype circuit with an input voltage in the range of 90–130 Vrms (60 Hz) and an output voltage of 48 Vdc The experimental results show that the THD of the input current is less than 13 4% under different input voltages and output powers Moreover the prototype circuit shows a maximal efficiency of 90 7%

Date of Award	2015 Jul 27
Original language	English
Supervisor	Hong-Tzer Yang (Supervisor)