Research Of Flyback LED Constant Current Power Supply With Lossless Snubber PFC

With the increasing serious environmental pollution and energy crisis, the semiconductor light emitting diode (LED) for its advantages of environmental protection, high efficiency, safety and reliability has been recognized gradually. While the power supply for LED on the market is irregular with low power factor and reliability, the research for the stable and reliable LED driving power supply is imminent so far.A harmonic current standard of power electronic of power electronic equipment has been developed according to the International Electrotechnical Commission (IEC). In order to reduce the harmonic pollution caused by switching power on the power grid, the two stage circuit structure was adopted in project design. For eliminating the harmonic of power supply device, boost active power factor correction (APFC) technology with lossless snubber was applied in the front end circuit, and a flyback converter topology was used in the latter stage circuit to achieve precise constant current for driving the LED loads.The causes of switching loss in the circuit are analyzed in depth at first. The development status of power factor correction circuit and soft switching technology was studied in the meantime. In this paper, a lossless snubber auxiliary circuit was introduced that could achieve the soft switching, and the work modes of the circuit are discussed. The small signal model for the boost converter was established by using state space averaging method, and it was derived the system characteristics’ transfer function. The control feedback loop circuit model was designed and simulated analysis with MATLAB.Secondly, the electrical characteristics and driving mode of LED driver was presented. The LED was designed according to low-cost, safe isolation principle and the output constant current would drive loads by utilizing flyback circuit structure. The parameters of the clamp circuit of transformer and power drive circuit are optimization.Finally, an80W flyback driver power supply device with soft switching power factor correction was developed and tested. The relevant experimental waveforms were given.The experimental results show that the circuit could achieve a high power factor and realize the soft switching in a wide input voltage range. The switching loss was greatly reduced and work efficiency was increased. The output driving current was constant and accurate. The system was stable and reliable with good practical performance.