| With the increasing of people’s awareness of energy saving, LED is used in our life more and more for its advantage such as long lifetime, energy saving, safe, reliable and green. LED has become a hot research topic in the field of power electronics. As part of the research, high power LED lighting gets more and more attention. Based on the background, this project focus on wide input and output multi-channel LED driver, including two parts:high efficiency wide input and wide output cascaded buck-boost PFC converter and wide output multi-channel LLCC converter. Topology choosing, operating principle and design considerations are discussed in this paper.A boost/buck-boost Power Factor Correction (PFC) converter with wide output voltage is proposed in this paper. The converter operates in boost mode when input is lower than output and in buck-boost mode when input voltage is higher than output voltage. In order to reduce the reverse recovery loss in both operating modes, the converter can achieve boundary conduction mode with a pseudo constant-on-time (COT) control. Furthermore, with the improved Pseudo-COT control the input line current keeps smooth during the operating mode transitions. Theoretical analysis and design considerations for the proposed converter and control strategy are presented and verified by a prototype with universal input voltage and wide output voltage.In order to balance four LED strings, a new LLCC resonant converter with two secondary side windings in main transformer, two secondary resonant capacitors in and an additional current sharing transformer (CST) is proposed. Each secondary resonant capacitor can balance the currents in one pair of outputs. And it bears the DC output voltage difference between two outputs of each pair. Meanwhile, the CST is used to balance currents of two pairs. The circuit operation principle, steady state characteristic and design considerations are discussed. A prototype is built to verify the proposed current sharing circuit. |
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