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This paper proposes a new burst-mode driving method to increase the power-conversion efficiency (PCE) of a power supply at light load. The burst mode minimizes the power consumption by stopping the converter operation when load is light. The proposed method changes the off-period of the converter according to the load to achieve optimized efficiency across the entire load range. The PCE at 6% load was measured as 83.6% and 85.1% for 75-W flyback and LLC Half-bridge converters, repectively, when applying the proposed burst mode; these values were 8% and 16.5% higher respectively than those for the converters without it. Index Terms-Light load efficiency, power-conversion, dc-dc converter.Kyungmin Lee received the B.. His current research interests include the design of drive circuits for display devices and the modeling and characterization of semiconductor devices..

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This paper proposes voltage equalizer for lithiumion battery string. Proposed equalizer uses LC resonant tank for energy transfer between battery cells. LC resonant tank is connected to the cells by switch network and can store and release energy from any cell in the battery string. Therefore energy can be transferred from strong cell to weak cell directly, which is effective for both of top and bottom balancing. In order to improve balancing performance, adjustable speed structure is employed. Prototype was implemented for 5 cell lithium-ion battery string. Experimental results showed that proposed circuit is suitable for battery cell balancing.