A High-Efficiency Quasi-Single-Stage Bridgeless Electrolytic Capacitor-Free High-Power AC–DC Driver for Supplying Multiple LED Strings in Parallel

In order to design a high-efficiency, cost-effective, high-power driver for supplying multiple light-emitting diode (LED) strings in parallel, a novel single-stage bridgeless, soft-switched integrated AC-DC converter is proposed. The proposed converter can be derived by integrating the totem-pole bridgeless boost power factor correction (PFC) circuit and half-bridge LLC resonant converter. Therefore, the number of semiconductors in the line-current path can be significantly minimized, and the power losses in the secondary rectifier diodes and the primary switches can be dramatically reduced. Moreover, the twin-bus concept can be adopted to achieve the quasi-single-stage power conversion of the total LED driver with multiple LED strings load. In addition, this circuit allows removing the bulky electrolytic capacitors with short lifetime by increasing the bus voltage ripple, and thus, the long lifetime is another advantage of the proposed LED driver. The detailed operation principles and design considerations for the proposed converter are analyzed and discussed. The feature of the proposed solution was demonstrated using a 100-W hardware prototype with six LED strings. The experimental results showed the converter achieves full-range ZVS for primary switches and the efficiency of 94.5% under the 120 V input voltage.