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In this letter, a novel current sharing scheme for two-phase interleaved LLC converter based on virtual controllable voltage sources (VCVSs) is proposed. In each phase, the VCVS is constructed by an auxiliary winding of the other phase transformer inserted into the resonant tank. The equivalent input voltage of resonant tank, which is the composition of the equivalent ac input voltage and VCVS, can be regulated to achieve current sharing by modulating the phase-shift angle between the two phases. Meanwhile, good output current ripple cancellation effect can be naturally achieved with appropriate parameters of VCVSs. Detailed operation principle and design considerations of the proposed current sharing method are presented. Finally, a 12 V/40 A two-phase interleaved LLC prototype has been built up to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

A “one-and-a-half stage” forward-flyback converter for electrolytic capacitor-less light-emitting diode (LED) driver with high power factor (PF), high efficiency, low output ripple current, and long lifetime has been proposed and studied in this paper. The basic topology of the proposed topology is a single-switch forward-flyback converter for achieving high PF. In addition, a buck converter is inserted between the forward subconverter and the load for creating two paralleled power transfer paths. The most of input energy directly reaches the load through flyback subconverter, and only about 1/4 of total energy is transferred to the load through forward subconverter and buck converter. Therefore, the proposed topology is a “one-and-a-half stage” converter and can achieve higher efficiency than the traditional two-stage topologies. At the same time, power decoupling can be realized and the electrolytic capacitor can be eliminated. Optimal control scheme, detailed analysis, and design considerations for this improved converter are presented. Finally, an experimental prototype for 28 V/700 mA LED driver was built up to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

A novel integrated buck–flyback nonisolated power factor (PF) correction (PFC) converter is proposed in this paper. This new converter is an inherent integration of a buck converter and a flyback converter, which operates in either flyback mode or buck mode according to whether the input voltage is lower or higher than the output voltage. In this way, the dead zones of ac input current in traditional buck PFC converter are eliminated. Therefore, the proposed integrated buck–flyback nonisolated PFC converter can achieve high PF under universal ac input range, and its input current harmonics can easily meet the IEC61000-3-2 Class C limits. The efficiency of the proposed converter is not deteriorated obviously compared to the conventional buck converter. Detailed theoretical analysis and optimal design considerations are presented. A 100-W prototype was built up to verify the theoretical analysis of the proposed integrated buck–flyback nonisolated PFC converter. [ABSTRACT FROM PUBLISHER]