Abstract
A two-stage output current ripple-free flyback-buck AC-DC LED driver with high power factor is presented. The first stage is a flyback power factor correction (PFC) converter and the second stage is a ripple-free zero-voltage-switching (ZVS) synchronous buck converter. Nearly unity input power factor can be obtained by using a flyback PFC converter. In the second stage, the output capacitor is eliminated because the output current ripple is completely removed by utilizing additional circuit composed of a coupled inductor, a series inductor, and a series capacitor. Thus, the proposed circuit is suitable to long-lifespan LED driver. Moreover, by using synchronous switch, ZVS condition is satisfied in the main switches and also the reverse recovery problems in the body diode of switch are solved. Therefore, the efficiency, lifespan and the stability for LED driver is improved. A prototype LED driver for 80W is built up to verify theoretical analysis and experiment results are presented.
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