Research On Electrolytic Capacitor-free AC/dC Lightemitting Diode(LED)driver

Light-Emitting Diode(LED) has the advantage of high efficiency, long lifespan,small volume, energy saving and eco-friendliness. Due to the breakthrough of key technology, a lighting revolution based on efficient and green lighting has been emerged. LED driver is the key parts of the LED lighting system on which the whole system’s lifespan is directly depended. The lifetime of traditional AC/DC LED drivers is limited because of the electrolytic capacitor. Therefore, it is an important research on electrolytic capacitor-free LED driver. For eliminating the electrolytic capacitors, this paper investigate both electrolytic capacitor-free topologies,including three-port converter topology and single-stage topology.The basic idea of topology derivation for three-port converters are discussed proposed. Based on the power flow characteristics between the ports, two-input and two-out converter are combinated for the combined three-port converter topology,and the final topology absorbed by integrating the parallel subcircuit structure.Topologies of flyback is deducted for describing the ideas and procedures. In order to minimize the capacitance, the storage capacitor voltage is designed as a large ripple voltage on the high DC voltage so as to replace the electrolytic capacitors with ceramic capacitor or CBB capacitors.In a typical three-port converter topologies, for example, A detail analysis of the typical three-port converter topologies is describe, including the working principle, switch mode, parameter design and control circuits. Based on the analysis of the main circuit works, the key points of parameters are given. What’s more, the capacitance value and prototype devices parameters are determined by constructing the function of the main circuit parameters boundary conditions. The simulation results verified the correctness and feasibility of the control circuit of the main circuit works.An experimental prototype of 13.5W is built to verify the proposed topology.Experimental waveform at different input power conditions verify the correctness and feasibility of the proposed three-port non-electrolytic capacitor LED driver.Finally, a single-stage non-electrolytic capacitor LED driver is proposed though the combintion of the two-stage cascade circuit. The single-stage LED driver circuit contains two power converter only with one power switch. It can achieve PFC function, constant current output and overcome the flicker with a simple circuit structure. Simulation results verify the correctness and feasibility of the proposed single-stage non-electrolytic capacitor, and the capacitance is minimized to 3.3u F.。...