Solid-state switch-mode rectification converters have reached a matured level for improving power quality in terms of power-factor correction (PFC), reduced total harmonic distortion at input AC mains and precisely regulated DC output in buck, boost, buck-boost and multilevel modes with unidirectional and bidirectional power flow. This paper deals with a comprehensive review of improved power quality converters (IPQCs) configurations, control approaches, design features, selection of components, other related considerations, and their suitability and selection for specific applications. It is targeted to provide a wide spectrum on the status of IPQC technology to researchers, designers and application engineers working on switched-mode AC-DC converters. A classified list of more than 450 research publications on the state of art of IPQC is also given for a quick reference.

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A review of single-phase improved power quality AC-DC converters

This work presents single-stage regulators with power-factor correction (PFC) based on an asymmetrical half-bridge topology. The proposed regulator is formed from a boost converter with two coupled inductors and an asymmetrical half-bridge converter with the synchronous switch technique, and it is controlled with pulsewidth modulation to achieve zero-voltage switching (ZVS). The boost converter is operated in discontinues conduction mode to achieve PFC. With the coupled inductors, input current ripple and power factor can be improved significantly. The proposed regulator has the features of constant-frequency operation, ZVS, and low voltage stress imposed on the active switches. Moreover, the regulator can achieve high power factor, high power density, high efficiency, low switching loss, and low component count, which makes its applications at medium-power levels feasible. Experimental results have verified the discussed features of the proposed regulator.

A single-stage fast regulator with PFC based on an asymmetrical half-bridge topology

This paper presents the small-signal modeling, dynamic analysis, and control design of the asymmetrical half-bridge dc-dc converter that employs a clamp capacitor and a magnetizing inductor to accommodate pulsewidth-modulated operation with asymmetrical duty ratios. The circuit averaging technique is applied to extract the small-signal dynamics of the power stage, and a graphical loop-gain method is used to design the feedback compensation and analyze the closed-loop performance of the converter. The distinctive power-stage dynamics of the converter are addressed and design guidelines for voltage feedback compensation are established. The results of the control design and closed-loop analysis are substantiated by experiments using an experimental converter.

Small-signal analysis and control design of asymmetrical half-bridge DC-DC converters

Typically, in a half-bridge converter A DC blocking capacitor and inductance on the primary side combines with the inductor and capacitor on the secondary side to produce complicated converter dynamic characteristics that make converter stabilization difficult The disclosed system and methods enable converter stabilization by modulating, as a function of the voltage across the DC blocking capacitor, the feedback output error signal or the ramp signal for the PWM controller of the converter The modulation removes the effect of the resonant circuit formed by the primary inductance and the DC blocking capacitor in the output voltage regulation loop Further adjustment of the duty cycle of the power switches enables keeping the output voltage undisturbed by voltage variation across the DC blocking capacitor Since, this inner compensation loop results in the voltage regulation feedback loop respond to only the output inductor-capacitor filter, the transfer function of this loop displays second order characteristics from the fourth order Hence, stability issues are simplified to conventional second order compensation network whereby the converter can be optimized for fast transient response

Apparatus for improving stability and dynamic response of half-bridge converter

This paper presents a unified analysis of half-bridge converters with current-doubler rectifier using an averaged circuit model. The model is applicable for both symmetrical and asymmetrical control. Different approaches to integrating the transformer with the inductors are discussed and their equivalent circuit models for use with the averaged converter model are developed. In addition, an inductor loop formed by the transformer and the two filter inductors is identified, and its effects on converter operation and control design are discussed. Numerical simulation and experimental results from a prototype converter are also reported.

Unified analysis of half-bridge converters with current-doubler rectifier

A small-signal model of soft-switched asymmetrical half-bridge DC/DC converter operating in a continuous inductor conduction mode is proposed. The analysis of this model is applicable to converters with any type of output rectifier (full-wave or half-wave). Based on the proposed model, the feedback compensation network for a prototype converter was designed. An open loop frequency response and voltage ripple attenuation of the converter with closed feedback loop were calculated. The experimental results validated all theoretical predictions. >

Small-signal modeling of soft-switched asymmetrical half-bridge DC/DC converter

Single-stage PFC AC/DC power converters promise lower cost and simplicity than two-stage converters. This is especially important for low power converters. A new family of single-stage PFC converters is proposed where an asymmetrical half-bridge DC/DC converter (AHBC) is utilized as a DC/DC cell. AHBC topology allows for a ZVS condition in its complementary driven switches. Retaining this property in the proposed AC/DC converter substantially enhances its efficiency. The circuits exhibit extreme simplicity while providing well-regulated output with low ripple and good power factor.

Asymmetrical half-bridge in a single stage PFC AC/DC converter

A new AC/DC power converter with high power factor is presented. This power converter has the advantages over both standard two-stage power factor corrected AC/DC power converters and single stage PFC power converters. These advantages are the overall simplicity of the power train, an optimised steady DC voltage maintained across the DC cell, constant operating frequency, inherent inrush current limiting capability, high efficiency due to the chosen topology's inherent ZVT capability and simple and inexpensive control circuits. The principle of operation is discussed and the design procedure for the power mesh is proposed. The small-signal model of the PFC cell is included.

A. Nemchinov

Papers

Small-signal modeling of soft-switched asymmetrical half-bridge DC/DC converter

Asymmetrical half-bridge in a single stage PFC AC/DC converter

Integrated AC/DC converter with high power factor