A review of high-performance, state-of-the-art, active power-factor-correction (PFC) techniques for high-power, single-phase applications is presented. The merits and limitations of several PFC techniques that are used in today's network-server and telecom power supplies to maximize their conversion efficiencies are discussed. These techniques include various zero-voltage-switching and zero-current-switching, active-snubber approaches employed to reduce reverse-recovery-related switching losses, as well as techniques for the minimization of the conduction losses. Finally, the effect of recent advancements in semiconductor technology, primarily silicon-carbide technology, on the performance and design considerations of PFC converters is discussed.

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State-of-the-art, single-phase, active power-factor-correction techniques for high-power applications - an overview

A novel zero-voltage and zero-current-switching (ZVZCS) full-bridge (FB) pulse-width modulated (PWM) converter is proposed. The new converter overcomes the limitations of the zero-voltage-switching (ZVS)-FB-PWM converter, such as high circulating energy, loss of duty cycle, and limited ZVS load range for the lagging-leg switches. By using the DC blocking capacitor and adding a saturable inductor, the primary current during the freewheeling period is reduced to zero, allowing the lagging-leg switches to be operated with zero-current-switching (ZCS). Meanwhile, the leading-leg switches are still operated with ZVS. The new converter is attractive for high-voltage (400-800 V), high-power (2-10 kW) applications where IGBTs are predominantly used as the power switches. The principle of operation, features, and design considerations of the new converter are described and verified on a 2-kW, 100-kHz, IGBT-based experimental circuit.

Zero-voltage and zero-current-switching full bridge PWM converter for high power applications

A number of soft-switching pulse-width-modulated (PWM) converter techniques have been proposed, aimed at combining the desirable features of both the conventional PWM and resonant converters while avoiding their respective limitations. In this paper, three classes of zero-voltage soft-switching (PWM) converters (namely the zero-voltage-switched (ZVS) quasi-square-wave converters, ZVS-PWM converters, and zero-voltage-transition PWM converters) and two classes of zero-current soft-switching PWM converters (namely, the zero-current-switched PWM converters and zero-current-transition PWM converters) are reviewed, and their merits and limitations are assessed. Experimental results of several prototype of converters are presented to illustrate each class of converter.

Soft-switching techniques in PWM converters

In many single-phase power factor correction (PFC) applications, the power level can reach several kilowatts; and in some situations, the input voltage can be quite high too. For high power and/or high voltage applications, the major concerns of the conventional boost PFC converter are the inductor volume and weight, and losses on the power devices, which will affect converter cost, efficiency, and power density. In this paper, a three-level boost converter is adopted for single-phase PFC, which uses a much smaller inductor and lower voltage devices than the conventional boost PFC converter does, yielding high power density, high efficiency, and low cost. >

Single-phase three-level boost power factor correction converter

Soft-switching techniques have recently been applied in the design of DC-AC power converters, in order to achieve better performance, higher efficiency and higher power density. A substantial number of new topologies for different applications has been developed, however the amount of work that has been done in this field is not widely known. This paper is an attempt to classify the soft-switched DC-AC topologies in a simple and generic way. The topology classifications are based on the location of the resonant network (load, inverter bridge, and bus), the characteristic of switching waveforms (zero-voltage switching or zero-current switching), and the type of resonance (series or parallel), operating principles, performance, and design limitations are discussed. Some possible industrial applications of soft-switched DC-AC power converters are also addressed.

A review of soft-switched DC-AC converters

A new family of zero-current-transition (ZCT) pulse-width-modulated (PWM) converters are proposed. The new family of converters implements zero-current turn-off for power transistor(s) without increasing voltage/current stresses and operates at a fixed frequency. The proposed converters are deemed most suitable for high-power applications where the minority-carrier semiconductor devices (such as IGBTs, BJTs, and MCTs) are predominantly used as the power switches. Theoretical analysis is verified on a 100-kHz, 1-kW ZCT-PWM boost converter using an IGBT. >

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Novel zero-current-transition PWM converters

For high power switching power converters, IGBTs are more attractive than MOSFETs due to the lower conduction losses and lower cost. However, the slow turn-on and turn-off characteristics, especially the turn-off current tail of the IGBTs, cause severe switching losses, thus limiting the switching frequency. Several bridge-type converters which achieve soft-switching of IGBTs with the help of the fast-switching MOSFETs are proposed. Experimental results have verified the effectiveness of this scheme. >

E.X. Yang

Papers

Novel zero-current-transition PWM converters

Soft-switching of IGBTs with the help of MOSFETs in bridge-type converters