Single-stage single-switch AC-DC LED driver with high power factor

A single-stage single-switch AC-DC LED driver with high power factor is proposed to overcome the drawbacks of the conventional boost-flyback PFC LED driver. In the proposed LED driver, the boost PFC converter with discontinuous conduction mode (DCM) is adopted to achieve high power factor and the modified flyback DC-DC converter with dual input is integrated to provide electrical isolation and the regulated output voltage. In order to divide input of DC-DC module (dc-link capacitor), the transformer with dual-primary winding is used. Moreover, the leakage inductor currents are absorbed by the dc-link capacitors through a snubber diode and the maximum voltage stress is limited to double DC-link voltage. Therefore, there are virtually no conduction losses by snubber circuit. In additional, some input power is directly transferred to the load and the remaining power is stored in dc-link capacitor. Hence, the total power efficiency is improved. The presented theoretical analysis is verified by prototype of 50kHz and 80W converter.