Research On LED Driver With Resonant Soft Switching Condition Based On Current Balance Module

In comparison with traditional lighting sources,LED(Light-Emitting Diode)has many outstanding advantages,such as higher efficiency,longer service life and better ability in dimming,which has become the most popular lighting source.Due to the low power of a single LED,multiple LEDs are required to give out light simultaneously in series and parallel arrays to ensure the brightness requirements in common lighting application.According to the analysis of impedance characteristics,constant current drive can make LED to achieve longer life.However,the constant of total current of multiple strings is easy,but the current of each branch in parallel is different due to the dispersion of each LED’s parameters,which affects the service life and lighting quality of lighting source.In order to solve this problem,this paper proposes a kind of resonant inverter based on current balance module,which guarantees the balance of current automatically,and ensures the good performance in current-regulating of each branch through controller.In order to meet the relevant national standards about power factor,a boost active power factor correction circuit working in critical conductive mode is designed.400 V DC voltage output is obtained while ensuring unit power factor,which provides constant DC voltage for resonant inverter.Aiming at the problem in current balancing of LED’s parallel structure,the automatic current balance module is applied in the resonant inverter,which realizes the automatic current balancing of LED’s parallel structure,meanwhile obtains the soft switching in a wide range of input voltage.Based on the fundamental wave analysis method,analyze the output characteristics of the LC resonant inverter and the principle of the automatic current balance module.The load model of LED is established.On this basis,the correctness of the LC resonant inverter and the current balance module designed is verified by simulation.And parameters of the LC resonant inverter and the current balance module are given,which is also verified by simulation.The output of resonant inverter is controlled by PFM,which is not suitable to build small signal model in spatial state averaging method.The extended description function(EDF)is chosen to set up small signal modeling in this paper.On this basis,PI compensator parameters are designed according to the transfer Function and modified through experiments.On account of the analysis and calculation above,The experimental prototype of LED driver with resonant soft switching condition based on current balance module is built,and the corresponding experiments and research are carried out to prove the correctness of the theory analyzed above.By analyzing data and experimental waveform,it is proved that the established experimental prototype has reached the established indicators.