Analysis And Optimization On Lighting Surge Robustness Of Super-junction VDMOS For LED Driver

Super junction vertical diffusion metal oxide semiconductor field effect transistor has the advantages of fast switching speed,low on-resistance and high breakdown voltage,and has been widely used in Light-emitting diode(LED)lighting,chargers,inverters,etc..However,the super-junction VDMOS has limited ability to withstand transient ultra-high voltage,which is easily damaged under the impact of lightning surge and seriously affects reliability of the whole system.Therefore,it is of great significance to study the lightning surge mechanism of super-junction VDMOS for LED driver.This thesis carefully studies the LED driver,focusing on the working principle of super-junction VDMOS in the LED driver.The test platform and simulation platform are set up.The measured results show that in the lightning surge process,the transfer of the avalanche current path is an important factor in the failure of the device,and the failure point is located in the cell region.Combined with simulation analysis,it is found that the avalanche current path of super-junction VDMOS flows through the parasitic triode region,and the electric field under the trench gate increases significantly,causing parasitic triode turn-on and gate oxide breakdown during device turn-off.Four improved structures are proposed and their static electrical parameters as well as the internal current path and impact ionization rate of the device are compared,the super-junction VDMOS device with step-doped N-type drift region structure is selected,and the improved structure is taped out.The super-junction VDMOS device with step-doped N-drift region proposed in this thesis is based on the 50?m deep trench etching process.From the test results,it can be concluded that when the improved structure is used in a single-stage flyback LED driver,the lightning surge capability is increased from 800 V to 4000 V,and the lightning surge level reaches the highest national standard.