Design Of A Lateral Constant Current Device For LED Driver

Nowadays, LED received extensive attention due to its high luminous efficiency, safety, environmental protection and long life. The driver of LED also got great progress and different applications need to be mature makes all sorts of drivers be designed. In some simple lighting applications such as workshop, office, family, etc…, the IC driver solutions is not conducive to control the costs. However, LED can be driven by a current regulator diode(CRD) and the full bridge rectifier which is very cheap compared with IC driver solutions. In this thesis, the main task is to design a low cost high reliability CRD device.The CRD device consists of low channel doping and high channel doping structures. A large number of simulations have been done by MEDICI and TSUPREM4 to improve the current performance of the CRD. The channel length, dose of N-well and the drift region length which have great impact on the IV and BV characteristics are fully considered. A higher concentration gradient is achieved by RTA in the low channel doping structure to reduce the saturation voltage, and the cathode field plate is adopted to alleviate the channel-length modulation effect which lead to the bad saturated IV characteristic. Double RESURF technology has been applied in high channel doping structure to achieve the high breakdown voltage and the longer channel is applied to improve the IV characteristic.The termination structures of the CRD layout is simulated and optimized to ensure the device function will and a parasitic MOS structures is turned off by balance the position and length of the cathode and anode filed plate. In the aspect of reliability, electric migration and heat impact are fully considered. Two layers of metal are applied to increase the conductive area and heat dissipation on the surface of the device which can reduce the influence of the electric migration and the heat.At last, the single metal structure has been proven by the experiment. Experimental results show the BV of CRD is higher than 150 V and saturation voltage is lower than 4 V, and different current levels of device is achieved such as 20 mA, 30 mA, 60 mA.