Research On Multiple Mode Electrolytic Capacitor-Less LED Driver With High Efficiency Over A Wide Range Of Input Voltage

Light-emitting diode(LED)has many advantages such as high lighting efficiency,proper color rendering index,long life span,environmental friendly,fast response.LEDs have been widely used in street lighting,blacklight display,message signs,automotive and architectural lighting.The performance of LED lighting is often directly determined by LED driver,so LED driver should own these characteristics of high reliability,high efficiency and low cost.In order to further improve the performance of LED driver over a wide range of input voltage,a multiple mode electrolytic capacitor-less LED driver with high efficiency over a wide range of input voltage is proposed,the detailed research contents are shown as follows:Firstly,it points out that high bus voltage in high-line condition,low efficiency in low-line conditions and involving electrolytic capacitor are the main factors restricting the performance of LED driver in this paper.In addition,the performances of present LED drivers are compared,it is found that it's difficult for them to achieve high reliability,high efficiency and low cost over a wide range of input voltage,providing a foundation and direction for improving the performance of LED drivers over a wide range of input voltage.Secondly,for the problems of high bus voltage,high device voltage stress and high switching loss when LED drivers working in high input voltage conditions,the proposed multiple mode LED driver works in half voltage input mode(HVIM).The bidirectional switch is turned off,and the high input voltage is divided equally by the input capacitors,which reduces the bus voltage effectively,thereby improving the system efficiency and reducing the cost.Besides,on the basis of discussing the operating principles of the half voltage input mode,the parameter design,loss analysis and design steps are analyzed in detail,and the feasibility of the proposed LED driver in half voltage input mode is simulated and verified.Thirdly,in view of the problems of high loss and low system efficiency when LED drivers working in low input voltage conditions,the proposed multiple mode LED driver operates in full voltage input mode(FVIM).The bidirectional switch is turned on,and the proposed LED is a bridgeless structure,which reduces the loss of the rectifier bridge diodes in low input voltage conditions.In addition,on the basis of theoretical analysis,the feasibility of the proposed LED driver in full voltage input mode is verified by simulation,and the system efficiency of the two different working modes are compared.Finally,the feasibility and the effectiveness of the proposed LED driver are verified by an experimental prototype with rated power of 100 W.The bus capacitors of the prototype are film capacitors,which improves the reliability of the system.The experimental results show that for 220 Vrms input,the efficiency of the prototype is 92.5%,the power factor is 0.991,and the bus voltage is 316V;for 110 Vrms input,the efficiency of the prototype is 91.2%,the power factor is 0.995,and the bus voltage is 322 V.The experimental results prove that the proposed multiple mode LED driver can achieve optimized bus voltage and high efficiency over a wide range of input voltage.