Power Factor Correction (PFC) has been established for a long time to fulfill the harmonic standards. To meet the demand for a compact, efficient solution, a so-called True Bridgeless Single Stage PFC was recently introduced. By eliminating the input rectifier the efficiency is significantly improved. In addition, this topology provides galvanic isolation while employing only one single active switch. In this paper a True Bridgeless Single Stage PFC is analyzed, designed and characterized through measurements on a hardware realization. To optimize the converter with respect to efficiency, power density or cost, analytical expressions for all occurring voltages and currents in each component are derived. With the derived small signal model, the current and voltage compensator can be designed optimally, to ensure a stable and fast control behavior. In addition, a non-dissipative clamp circuit is introduced to limit the switch voltage without causing significant losses. The results of the theoretical analysis are verified by simulation and experimental measurements.
I. INTRODUCTIONTypically, in single phase systems, a boost PFC solution is employed which meets all the requirements with respect to the established standards and achieves at the same time an acceptable efficiency at the European voltage level. To satisfy the demand for universal input voltage, all the commonly employed PFC converters possess one major drawback. The input rectifier reduces the efficiency by approximately 3 % at low line (85 V), which often results in an overall efficiency lower than 93 %. Thus, the main objective is to eliminate the input rectifier to prevent this drop of efficiency. Several attempts have been proposed in the past to overcome this issue [1]- [8]. By replacing two diodes of the input rectifier with active switches, the low line efficiency can be improved; however there still remains one diode forward voltage drop which causes non-negligible losses. Additionally, in many applications galvanic isolation of the output is required. This leads to a multistage approach, typically with a boost PFC as input stage and a DC-DC stage for galvanic isolation. This causes additional losses as the output power must be processed in both stages. Typically this popular solution results in as many as 12 switches and up to four magnetic components. This often results in an overall efficiency of less than 90 %. In the past several attempts have been made to find possibilities of combining the current shaping PFC function with the DC-DC converter including galvanic isolation, so called single stage PFC converters. In all presented cases the input rectifier
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