Research And Design Of Led Lighting Power Supply

As a new generation of semiconductor solid state lighting source,LED has been widely used in street lamps,car lamps and LCD backlight.With the development of technology, filament lamps will be replaced by LED lamps, which will be the main device of general lighting in the future. However, the quality and life of LED lamps are determined by the driver, so the solutions of LED driver are researched in the thesis.The power factor of AC/DC converters used in LED lighting should be corrected, so that it could meet related standards. The single stage PFC power supply based on BCM flyback converter is used as the LED driver in the thesis. Under peak current control method, the on-time of MOSFET is kept constant to make the inductor peak current follow the rectified sinusoidal voltage. As a result, the phase of the input current is the same as the input sinusoidal voltage. In this way, the power factor of the LED driver is improved. This method is easy to control, cheap and light.The detailed calculation procedure of the BCM flyback converter is deduced. Meanwhile, parameters related to the power factor are pointed out, with higher input voltage, the PF is getting lower. Then, the real working process of the converter is discussed in the thesis.The LED driver based on BCM flyback PFC converter in this thesis is designed with L6562. The whole system is seperated into four parts:EMI filter, main circuit, control circuit and feedback loop. The design procedure of each part is researched detailly in the thesis, and the parameters are calculated carefully.In the end, the power system is simulated with LTspice and the demoboard is experimented, the results of the simulation and experiment are nearly the same. In88-264Vac input voltage range, the output current is around0.7A, the PF is more than0.95and the THD is less than15%. It is verified that the demoboard has passed the IEC61000-3-2Class C harmonic standard and the EN55015EMI Standard.