Design Of Led Power Supply System Based On Low Frequency Inverter AC Power Supply Method

With the continual improvement and progress of the society, LED lights gradually get into people’s life, and become the main force in the field of lighting. As the surroundings is changing, people’s demands on the environment are becoming higher and higher, and the high frequency pollution problem got the attention of people. So it is revealed that the traditional LED power supply system has the different kinds of disadvantages. At present, the high power LED driver supply electricity for the LED lights after AC-DC conversion to 220V electric supply and then DC-DC conversion, the circuit structure is complicated. DC-DC conversion produce high-frequency square wave whose amplitude is 250V-350V and frequency is 40-100 KHz. So the high electromagnetic interference brings about high frequency pollution to the environment. In order to overcome the above problems, the dissertation proposed a design of LED power supply system based on AC bus power supply mode with low frequency and variable frequency.This dissertation set adopts capacitor step-down mode with simple structure to drive LED lamp which replaces DC-DC converter. This way can greatly reduce electromagnetic interference and solve the problem of high frequency radiation, meanwhile, the power consumption only exits in the bridge rectifier circuit in conversion process. So it improves the conversion efficiency of electric energy. Firstly, in order to use the converter based on capacitor step-down mode to drive the LED units with high power and do not increase the capacitor capacity at the same time, we need to improve the frequency of input voltage. In this dissertation, a mathematical model of the frequency and power of the non continuous mode capacitor buck circuit is derived, and the frequency of 200Hz is determined.Secondly, in order to get 200Hz sine wave, in the dissertation it is designed that high efficiency sine wave frequency conversion power supply as LED power supply system based on Design of APFC technology and DC-AC Technology. It provides 200Hz sine wave to the extension set. In main energy, the first stage is DC-DC converter based on APFC mode using L6561 chip, it transform alternating current to direct current with 370V-400V. The second stage is sine wave inverter with high efficiency, it transform direct current to AC sine wave voltage with 200Hz and 250V valid values.Finally, in the dissertation, it is confirmed that the best LED load voltage is 120V through building the mathematical model of mower and load voltage in capacitance step-down mode, and finished designing LED driving circuit of the extension set.In this dissertation, it separately tested and analyzed main energy and extension set of the LED power supply system. The measured data show that variable frequency power supply can obtain stable output voltage with 200Hz、 250V valid values sine wave. LED driving power supply of the extension set can provide stable 120V DC voltage with 1V ripple. It has excellent characteristic of constant power. The power conversion efficiency of LED can be 95%. Compare with the LED driver based on DC-DC step-down mode; substantially reduce the high freauencv radiation and electromagnetic interference.