A bridgeless electrolytic capacitor-free LED driver based on series-resonant converter with constant frequency control

High-brightness light-emitting diode (LED) is next generation of green lighting with high luminous efficiency and long life. The bulky electrolytic capacitors are required to balance the pulsating power difference, thus restricting the driver lifetime. However, the existing LED drivers using pulse frequency modulation (PFM) is bound to arouse heavy electromagnetic interference(EMI). In this paper, a series resonant converter (SRC) is proposed to eliminate the low frequency ripple. Meanwhile, the switching controlled capacitor (SCC) is used to replace the resonant capacitor to achieve full range operation with constant switching frequency. Half-bridge switches are shared by integrating the bridgeless boost power factor correction (PFC) circuit and the power control (PC), so as to realize the single-stage drive. Furthermore, the SCC is shared by the outputs of upper and lower half-bridge, which reduces the volume. All the superior performance of proposed LED driver is verified by simulation with 2-channel LEDs, rated output power of 100W.