Research On High Frequency LLC Power Converter With Resonant Gate Driver

The rapid development and wide use of semiconductor technology and microelectronics technology,provide a technical possibility for the power converter to high frequency,miniaturization and high power density of the direction of development.LLC converters are widely applied in communication power,lighting,AC-DC and other fields due to their advantages of small loss,high efficiency and high power density.However,with the increasing of the switching frequency(>1MHz),the drive losses and switching losses of the traditional voltage source driver(Voltage Source Driver,VSD)are also increased in proportion,thereby reducing the efficiency of the LLC converter.Thus,in order to solve this problem,A new resonant drive technology —— resonant gate drive technology was put forward.With the principle of LC mutual transfer energy,the resonant driving circuit recycles the driving energy stored on the input parasitic capacitance of the power MOSFET tube,which reduces the high frequency drive loss.The driving losses of the two resonant drive circuits are obtained by using the optimized resonant inductance value.At the same time,the driving loss contrast between the two resonant drive circuits and the traditional VSD drive circuit is given.First,this dissertation introduces the research background and research status of the resonant drive technology,and divides the existing resonant drive circuits into resonant drive circuit of sinusoidal current(Resonant Gate Driver,RGD)and resonant drive circuit of current source(Current Source Driver,CSD)with the shape of resonant current.At the same time,CSD circuits can be divided into CSD with continuous resonant inductor current and CSD with intermittent resonant inductor current.Then,the isolated RGD for the primary power MOSFETs and the CSD with continuous resonant inductor current for synchronous rectifiers are studied.The working principle,the loss and calculation method of the two resonant drive circuits are analyzed in detail.In order to design the optimal resonant drive circuit,the resonant inductance is optimized by considering the relationship between the drive loss of the resonant drive circuit and the switching loss of the power MOSFET or the diode loss.In addition,thelosses of the two resonant driving circuits with optimized resonant inductance and the VSD circuit are compared and analyzed.Finally,in order to verify the correctness of the theoretical analysis,in this dissertation,the principle prototype is made based on half bridge LLC topology with synchronous rectification.The experimental debugging is completed,at the same time,the experimental results and detailed analysis are given.