Research Of LED Driving Power Supply Based On Dual Switch Flyback

With the increasing pressure threaten by the resource energy globally, energy saving and environmental protection has been paid more and more attention. Electricity consumption in lighting is an important part of power consumption. Therefore, it is with great significance to reduce the energy consumption of lighting. LED(Light Emitting Diode, LED), recognized as the fourth generation light source, has the advantages of long service life, high photoelectric conversion efficiency, safety, environmental protection and so on. However, the LED is relatively high demand for the driving power supply. At present, LED driving power supply has become a bottleneck which restricts the development of LED. This paper is based on the topology of the dual switch flyback and designs a driving power supply for LED which is with small electrolytic capacitors, high power factor and high reliability.This paper is organized as follows:Firstly, this paper introduces the application status and development prospects of LED as well as the research background and significance of high reliability of LED driving power supply. The destination of this paper is to develop a LED driving power supply with high power factor, high efficiency, high reliability and long lifespan, which is based on the analysis of the existing problems of LED driving power supply as well as the development trend of LED driving power supply.Secondly, the dual switch flyback is chosen as the main circuit topology through the introduction of several common switching power supply topology and the comparison of their advantages and disadvantages. Furthermore, the synchronous and asynchronous operating state of the two switch tubes in the dual switch flyback converter is analysed. When the two switch tubes is in asynchronous operating state, the energy loss is much larger. So it is better to make the two switch tubes in the synchronous state. The two switch tubes in the dual switch flyback circuit were droved by the isolated transformer, which will allow them to work in the synchronous state and therefore reduce energy consumption as much as possible. In order to remove the electromagnetic interference caused by the input side, the EMI filter is designed for the input of the driving power supply. The parameters of the transformer are calculated through the analysis of the working state of flyback transformer and the dependent on actual demand. Due to the great harm of the leakage inductance in the dual switch flyback converter, some methods to reduce the leakage inductance of transformer are given in this paper.Thirdly, the use of large electrolytic capacitors in the input side is replaced by the single stage PFC circuit with chip control. The reduction of power consumption is achieved by optimizing the power supply circuit of the chip. And the design of the peripheral circuits of the main control chip is completed. In order to provide the reliable power supply for LED loads, the calculation of the output voltage and the output current feedback loop parameters and the design of the protection circuit as well as the choice of the output end rectifier diode and filter capacitor are done.Finally, the experimental prototype is tested, and the waveform of the key components of the power supply is given. The performance of the power supply is tested under the condition of different input voltages. In the input voltage of the AC 220V, the efficiency of the power supply is 87.04% and the power factor is 0.968. Besides, the components with large power consumption in the circuit are analyzed.