In this paper, a single-stage LED driver is proposed for a street lighting system. Two boost circuits that share a single inductor are formed by integrating the switches of a half-bridge $LLC$ resonant converter. Both boost circuits operate in the boundary conduction mode, which realizes a power-factor correction function. Because the input voltage of the LED driver is divided by two capacitors, the bus voltage is considerably reduced to almost the input peak voltage, rendering the novel single-stage LED driver to work suitably under high-input-voltage conditions. The soft-switching characteristics of the half-bridge $LLC$ resonant circuit are not affected by the integration of the switches; thus, the converter has a low cost and a high efficiency. A 100-W prototype was developed, and the efficiency was determined to be as high as 91.1% in a full-load state under a 220-V ac input.

A Single-Stage LED Driver Based on BCM Boost Circuit and $LLC$ Converter for Street Lighting System

This paper proposes a new bridgeless single-stage half-bridge ac-dc converter for power factor correction. The proposed converter integrates the bridgeless boost rectifier with the asymmetrical pulse-width modulation half-bridge dc-dc converter. The proposed converter provides an isolated dc output voltage without using any full-bridge diode rectifier. Conduction losses are lowered by eliminating the full-bridge diode rectifier. Zero-voltage switching of the power switches reduces the switching power losses. The proposed converter gives a high efficiency, high power factor, and low cost. The effectiveness of the proposed converter is verified on a 250 W (48 V/5.2 A) experimental prototype. The proposed converter achieves a high efficiency of 93.0% and an almost unity power factor for 250 W output power at 90 Vrms line voltage.

A Bridgeless Single-Stage Half-Bridge AC/DC Converter

Single-phase power factor correction (PFC) ac-dc converters are widely used in the industry for ac-dc power conversion from single phase ac-mains to an isolated output dc voltage. Typically, for high-power applications, such converters use an ac-dc boost input converter followed by a dc-dc full-bridge converter. A new ac-dc single-stage high-power universal PFC ac input full-bridge, pulse-width modulated converter is proposed in this paper. The converter can operate with an excellent input power factor, continuous input and output currents, and a non-excessive intermediate dc bus voltage and has reduced number of semiconductor devices thus presenting a cost-effective novel solution for such applications. In this paper, the operation of the proposed converter is explained, a steady-state analysis of its operation is performed, and the results of the analysis are used to develop a procedure for its design. The operation of the proposed converter is confirmed with results obtained from an experimental prototype.

Analysis and Design of a New AC–DC Single-Stage Full-Bridge PWM Converter With Two Controllers

This paper discusses the major issues that exist in the single-stage ac/dc converters with power factor correction (PFC) and presents a novel converter based on a quasi-active PFC scheme. Two additional windings wound in the transformer of a conventional dc/dc flyback converter are used to drive and achieve continuous current mode operation of an input inductor. In addition, direct energy transfer paths are provided through the additional windings to improve the conversion efficiency and to reduce the dc bus capacitor voltage below 450 V for universal line applications. The proposed converter can be easily designed to comply with IEC 61000-3-2 Class D requirement and to achieve fast output voltage regulation. By properly tuning the converter parameters, a good tradeoff between efficiency, dc bus capacitor voltage stress, and harmonic content can be achieved. Operating principles, analysis, and experimental results of the proposed method are presented.

A Single-Switch AC/DC Flyback Converter Using a CCM/DCM Quasi-Active Power Factor Correction Front-End

The single-stage forward-flyback power factor correction converter with quasi-resonant (QR) control is studied in this paper. This converter merges flyback converter and forward converter through a common transformer. Only the flyback subconverter works when the input voltage is lower than the reflected output voltage while both the flyback subconverter and the forward subconverter operate to share the output power in the rest region. The dead zones which exist in the ac input current of traditional forward converter are eliminated and high power factor can be achieved. Two different QR control schemes have been studied. Detailed analysis, optimal design considerations, and comparison for these two QR control modes are provided. Finally, two 120 W experimental prototypes for LED driver were built up to verify the theoretical analysis.

Study on the Single-Stage Forward-Flyback PFC Converter With QR Control

A new single-stage power factor correction (SSPFC) converter is proposed for the adapter application, which is composed of a flyback converter, a feedback winding and a front-end input current shaper. Through the feedback winding, a direct energy transfer path is configured to improve the conversion efficiency and alleviate the voltage stress across the bulk capacitor. Moreover, the feedback winding is connected to the input through only two diodes, which results in low conduction losses. Equations and configurations are given to design the input current-shaping inductor and the magnetizing inductor of the transformer, which are operated in the discontinuous conduction mode (DCM) and the DCM/ continuous conduction mode boundary mode respectively for well-shaped current waveform and reduced bulk capacitor voltage. The theoretical analysis of the converter is verified by two SSPFC prototype circuits with 19 V/90 W output. One prototype achieves a high efficiency of 90.3%, while complying with IEC 61000-3-2 Class D standard. With a different turns ratio design, the power factor can be further improved to 0.97 in another prototype.

Design and Analysis of Single-Stage Power Factor Correction Converter With a Feedback Winding

A new single-stage power factor correction (SSPFC) converter is proposed for the adapter application, which is composed of a flyback converter and a front-end input current shaper. Low conduction losses are achieved with only two diode conduction drops in the primary side. The conversion efficiency is improved with a direct energy transfer path, which is provided by the feedback wingding. Equations and configurations are given to design the input current shaping (ICS) inductor and the magnetizing inductor of the transformer operating in discontinuous conduction mode (DCM) or in DCM/CCM boundary mode. The good performance of the converter is verified experimentally on a 90W (19V/4.74A) SSPFC converter with universal line input.

Ye Xu

Papers

Design and Analysis of Single-Stage Power Factor Correction Converter With a Feedback Winding

Single-stage power factor correction converter with coupled input current shaping inductor