(A) new single-stage power factor correction AC/DC converter topologies with low voltage stress for universal line application

Abstract

Nowadays, the power factor correction(PFC) has become mandatory in ac/dc converters to meet tight regulations such as an IEC 61000-3-2 standard. A single-stage power processing has been widely adopted due to the cost-effective and simple control compared to a two-stage approach even though a two-stage approach shows better performances than a single-stage ones. It is well known that the boost PFC stage can shape an input line current to a sinusoidal waveform under the discontinuous conduction mode(DCM). Thus, most of ac/dc converters have integrated the output dc/dc converter with the boost PFC stage to obtain the single-stage PFC converters. The major problem of these types of PFC converters is a high voltage stress across the link capacitor and active power devices at high line input and light load conditions. Therefore, it is necessary to develop converter topologies to solve this problem for universal line applications. In this thesis, a new concept and topologies are proposed for a single-stage PFC ac/dc converters. Based on flyback topology, a single-stage zero-current-switching(ZCS) quasi-resonant ac/dc converter with low dc link capacitor voltage is proposed. It has many advantages such as simple circuit, cost-effective, and high power density for low power applications. The proposed converter can effectively reduce the voltage stress on the dc link capacitor and can achieve the power factor correction without a dead band at line zero-crossings, which improves the harmonic distortion in ac line current. Furthermore, it is possible to reduce the power loss of a semiconductor power switch by making use of zero-current switching quasi-resonant operation. However, the converter has a disadvantage such that input filter design is very difficult because of a variable switching frequency control. To solve this problem, a single-stage, single-switch bi-flyback ac/dc converter is proposed. The main flyback stage controls the output power from the link capacitor ...