A Design Of SCR With Low Temperature Coefficient Of Trigger Current

Since SCR was invented in the 1950 s,it is becoming more and more important in modern life during last sixty years.Because of its good performance on speed change and frequency modulation,SCR is widely used in the industry.Also,SCR is used in the field of consumer electronics like leakage protector,white good and motorcycle.According to the magnitude of trigger current,there are two kinds of SCR: standard SCR and sensitive SCR.The trigger current of Sensitive SCR is low and the power consumption of gate is low,too.So sensitive SCR becomes popular,but its trigger current varies greatly when temperature changes.The trigger current of sensitive SCR will become lower when it works at high temperature,this will lead to erroneous trigger even sensitive SCR will keep in conduction.On the other hand,the trigger current of sensitive SCR will become higher when it works at low temperature,this will cause higher power conduction of gate.This paper will provide some methods to lower temperature coefficient of trigger current both at low temperature and high temperature,also provide a design of SCR with low temperature coefficient of trigger current to make sensitive SCR can operate steadily at high temperature.The aim of main parameters are as follows: forward blocking voltage and reverse blocking voltage are bigger than 800V;break-over voltage is less than 2V;the trigger current at 25? is less than 100?A;the ratio of trigger current at 80? and 25? is bigger than 0.5.This paper includes following parts:1.Introduce the trigger principle of SCR,analyze why the value of trigger current changes with temperature and propose the method to lower the temperature coefficient of trigger current both at low temperature and high temperature.2.Simulate SCR with ploy resistance.Complete layout design.3.After simulating the device and designing the layout,carry on tapeout test.Test results are as follows: forward blocking voltage is 800 V,reverse blocking voltage is 1000V;forward leakage current at 125? is 35?A,reverse leakage current at 125? is 50?A;trigger current at 25 ? is 60?A,trigger current at 80 ? is 36?A,the temperature coefficient of trigger current is 0.6;break-over voltage is 0.96V;the critical di/dt is 18A/?s,the critical dv/dt is 20V/?s.Test results indicate this design meets the requirements basically.