Analysis And Optimization Of Emi Characteristics Of Diode In Hybrid Vehicle Drive System

With the promotion of hybrid electric vehicles(HEV),more and more attention has been paid to the electromagnetic interference(EMI)of HEV.The application of power MOSFET,IGBT and other advanced switching devices in HEV puts forward higher requirements for matching diodes,so it is necessary to develop new structure power diodes.Super junction theory breaks through the traditional "Silicon limit" and has been applied to all kinds of power devices.In this paper,super junction structure is introduced into JBS diode to form super junction JBS diode.Based on the requirements of hybrid electric vehicle drive system for devices,on the basis of the working principle and structural parameter optimization design of super junction JBS diode,a super junction JBS power device with low EMI is proposed Structure and process design of diode.Firstly,this paper analyzes the electromagnetic environment of hybrid electric vehicle,the working principle of driving system circuit and the EMI mechanism of diode in driving circuit.On this basis,the initial model of super junction JBS diode is established,and the working mechanism and characteristics of super junction JBS diode are analyzed.The effects of p-pillar concentration and n-pillar concentration on the device properties were analyzed by numerical method,and the structure parameters were optimized.Aiming at the problem of fast current conversion and large di/dt in the reverse recovery process of general super junction JBS diode,a low EMI super junction JBS power diode is designed by improving the structure.The new super junction JBS power diode can not only reduce di/dt in the reverse recovery process,but also be realized by ordinary manufacturing process(1)The driving system of hybrid electric vehicle is analyzed to understand the source of EMI.The drive system of hybrid electric vehicle includes power conversion system.The power conversion system will produce high-speed switching of large current,and then through the parasitic inductance,leakage inductance and parasitic capacitance in the circuit system,it will produce large EMI.(2)Based on the analysis of the generation mechanism of EMI source in the drive system of hybrid electric vehicle,it is known that the “imperfect” switching characteristics of power diode is one of the causes of EMI.The voltage and current spikes generated by the pin diode in the traditional hybrid electric vehicle drive system in the switching process are broadband EMI,which is an important source of EMI in the hybrid electric vehicle drive system.(3)By comparing various kinds of power diodes,this paper selects super junction JBS diodes to alleviate the EMI problem of HEV.The diode structure parameters of the super junction JBS are optimized,and the characteristics are simulated and analyzed.Super junction JBS diodes not only maintain the high speed switching characteristics of unipolar devices,but also can bear high blocking voltage while maintaining good forward conduction characteristics.The disadvantage is that too fast reverse recovery speed results in large di/dt,and the manufacturing process is complex.(4)The structure and process design of low EMI super junction JBS diode.The new super junction JBS diode adopts the common diffusion process.By increasing the area of the transverse PN junction,the di/dt in the reverse recovery process is reduced,which is more conducive to reducing the EMI of the hybrid electric vehicle drive system.The diffusion process used in the new super junction JBS diode greatly reduces the difficulty of the super junction device manufacturing process.