Research And Design Of LED Driver With High Power Factor

As an efficient and environmentally friendly lighting devices,LED has not only become a research focus of lighting technology,but also has driven the development of the drive power industry.Combined with the operating characteristics of LEDs,switching power supplies are widely used in the design of driving power supplies due to their small size and high efficiency.However,as more and more lighting equipment is connected to the power grid,switching power supply will causes problems that harmonic pollution of power grid and low power factor of equipment,and these problems restrict the use of LED.In order to solve the problem of low power factor of equipment,a high power factor LED drive power supply structure is proposed,which can effectively improve the power factor and efficiency of the system.The system consists of a rectifier circuit with PFC function and an LED drive circuit.The output voltage of the rectifier circuit is used as the power supply voltage of the LED drive circuit.Among them,the PFC rectifier circuit works in the critical conduction mode,with the L6562N chip as the control core,and use the flyback converter as the basic topology,to realize the buck output function.By controlling the peak current of the primary inductor,the phase of the input current follows the input voltage,to realize the function of power factor correction of the system.The LED drive circuit uses the LM3464 chip to control four load output channels,and the external PWM dimming circuit adjusts the load brightness.At the same time,the internal thermal feedback circuit of the chip will adjust the current of output channels,according to the load temperature change.In addition,the dynamic headroom control module in the LM3464 chip detects the voltage of LEDs at different temperatures,and feedback to the PFC rectifier circuit to adjust the output voltage.Therefore,the current supply voltage of LED driver circuit is matched with the change of the load voltage,and the efficiency of the system is improved.Use Saber to simulate the PFC rectifier circuit,and according to the system design plan,develop an experimental prototype.The input is AC mains.After testing,the power factor of the prototype is 0.95 and the efficiency is above 80%.Finally,a comparative analysis of the test results and data verified the correctness of the theoretical analysis and the feasibility of the system design method.