Design Of The Structure Of 600V Super-junction VDMOS For The Low EMI Noise And High Efficiency In Flyback Switching Power Supply

Flyback switching power supply has been widely applied in power supply charger of mobile information devices thanks to its high energy efficiency,simple circuit and low cost.Super-junction vertical-diffused metal-oxide-semiconductor field-effect transistor,as a power switching device in flyback switching power supply,has advantages of high breakdown voltage,small on resistance and fast switching speed.However,the over fast switching speed of super-junction VDMOS will result in strong radiation electromagnetic interference noise in the system and seriously influence the performence of whole system.So researching the mechanism on the radiation EMI noise of super-junction VDMOS is a great meaningful work.Firstly,a radiation EMI noise testing platform for system is set up and from the testing results it can be obtained that the radiation EMI noise is bigger with rate of zero turning on current peak becoming faster.Then combining theory of the loop radiation noise and current characteristics of super-junction VDMOS to analyse and derive,it is found that the radiation EMI noise can be reduced by increasing gate platform voltage,gate capacitance and gate resistance of device.Whereafter,a radiation EMI noise simulation platform for device is set up and harmonics of zero truning on current of present devices are simulated to verify aforementioned conclusions with test of near field radiation.Further,a grid trench gate super-junction VDMOS structure is proposed,which uses grid gate structure to increase gate capacitance effectively.Its gate platform voltage and gate capacitance are designed from the perspective of the radiation EMI noise and switching characteristics.The feature of high energy effeiciency of this strcutrue is guaranteed and the radiation EMI noise is dramatically reduced under the same condition of system.The grid trench gate super-junction VDMOS proposed and designed by this thesis is fabricated basing on the 600V deep trench etching process.The final test results show that the peak value of normalization radiation noise spectrum of system applied with the device proposed in this thesis is low to 37.81dB?V/m under the national standard,and other parameters of device are kept in present levels.The results meet the design objective and the application requirement of flyback switching power supply.