Comparison among High-Frequency and Line-Frequency Commutated Rectifiers Complying with IEC 61000-3-2 Standards José Antenor Pomilio School of Electrical and Computer Engineering, University of Campinas C. P. 6101 13081-970 Campinas – BRAZIL Tel. (+55.19) 7883748 – Fax (+55.19) 2891395 e-mail: antenor@dsce.fee.unicamp.br Giorgio Spiazzi, Simone Buso Department of Electronics and Informatics, University of Padova Via Gradenigo 6A - 35131 Padova - ITALY Tel. (+39.049) 827-7503/7525 - Fax (+39.049) 827-7699/7599 e-mail: giorgio.spiazzi@dei.unipd.it – simone.buso@dei.unipd.it Abstract - High power factor rectifiers, complying with IEC 61000-3-2 standards have been deeply studied. Two main approaches are usually used: high frequency control of the input current (as in PFCs) and line-frequency commutated rectifiers. The latter represent an interesting solution for large volume applications which do not need a precise output voltage regulation. They provide compliance with a smaller overall reactive component volume as compared to conventional rectifiers with passive L-C filter. Moreover, being the switch turned on and off only twice per line period, the associated losses are very small and the di/dt and dv/dt can be lowered compared to high-frequency commutated rectifiers, thus reducing the high-frequency noise emission and EMI filter requirements. This paper reviews the operating principles of some line-frequency commutated rectifier topologies highlighting their merits and limitations. A comparison among low and high frequency high power factor rectifiers, in terms of circuit complexity, overall reactive component size and performance, is made, thus allowing selection of the most convenient topology for a given application. I. INTRODUCTION High quality rectifiers (also called Power Factor Correctors - PFCs) are rapidly substituting conventional front- end rectifiers due to the low-frequency harmonic limits imposed by international standards like IEC-61000-3-2 [1]. Such high-frequency commutated rectifiers provide very high power factors (actually much higher than what is required by the standards) and a good output voltage regulation, at the expense of an increase of the overall ac-to-dc converter size and cost. The PFC based on the boost converter (HF – boost PFC) operating in the continuous conduction mode (CCM) is the preferred choice, especially in the medium power range. Nevertheless, some large volume applications still use standard low-cost, high-reliability rectifiers with passive filters in order to improve the quality of the current drawn from the line, even if the volume of the reactive components needed rapidly becomes prohibitive as the power increases [2]. Recently, different line-frequency commutated rectifier topologies were proposed as a trade-off between high-frequency PFCs and completely passive solutions [3-7]. Compliance with IEC-61000-3-2 can be achieved with a reduced overall reactive component size compared to passive solutions. All of them utilise a switch which is turned on and off only twice per line period, thus drastically reducing both conduction and switching losses. Moreover, the limited di/dt and dv/dt during the commutations allow reduction (or even elimination) of the high-frequency noise emission and of the EMI filter requirements. In this paper, some of these different line-frequency commutated rectifier topologies are reviewed with the aim of providing the tools for the best choice for a given application. A comparison with a boost-type high-frequency commutated PFC is made, observing aspects as: input current distortion and output voltage regulation, circuit complexity, switch current and voltage stresses, reactive component size, etc. Such evaluation is carried out for different power levels, ranging from 300 W up to 1.2 kW. II. LINE-FREQUENCY COMMUTATED RECTIFIER TOPOLOGIES The schemes of the line-frequency commutated rectifier topologies that are taken into consideration are shown in Fig.1. Each of them contains a line frequency smoothing inductance, L, and an output filter capacitor, C, plus an auxiliary switching unit. Such unit consists of a line-frequency commutated switch, S, plus a diode, D. Topology T2 also uses an auxiliary capacitor, C a , and an auxiliary inductance, L a . Except for diode D, the auxiliary elements are all rated at a small fraction of the output power. Topology T1 is electrically identical to the HF - boost PFC. These rectifiers allow compliance with low-frequency harmonic standards, with a reduced smoothing inductor value as compared to passive L-C filters. The principles of operation are now briefly reviewed. 0-7803-6404-X/00/$10.00 (C) 2000