Research And Design Of High Voltage LED Constant Current Drive Circuit

New generation light source LED of its advantages of non-polluting, high reliability, long life, energy saving and environmental protection is more and more used in displays,lighting and other fields.LED's self-physical characteristics determines the need of drive circuit for its use to ensure generates reliable light sources, while this control must be a current control, to ensure a constant of the LED light. Therefore, the current control LED driver IC design plays an important role on the development of LED lighting. At present, for the input voltage is not very high LED lighting systems, usually battery powered. Takes into account the instability of battery the driving performance of the circuit is not ideal; and for direct use of electricity-powered lighting systems, often needs to build external AC-DC circuits. This will increase the cost and also more complicated to use.This paper combines reverse design and forward design and based on CSMC 0.5um BCD process, a high input voltage constant current LED driver IC is designed. This design including a DC-DC control circuit and using PWM modulation achieves a very good constant current drive goals, and it's contains fixed frequency and fixed off-time modes. In those two modes, the circuit provides constant current drive circuit, linear dimming, digital dimming, over voltage protection, short circuit protection features. By adjusting the resistance of RR1 and RR2 connected with IREF pin, constant current value can be achieved on the set, the output current range of 6mA-173mA. Circuit internal bandgap reference circuit generates 1.27V reference voltage, and the voltage can be provided externally as a reference. The input voltage can be range from 11V to 25V by the internal linear regulator circuit.Meanwhile, the supply voltage stabilized at 8.1V.This design doesn't need external voltage conversion circuit. Because of the used process, the highest voltage is limited at 25V. As long as achieve a higher voltage of the JFET the voltage of circuit can be improve. So the article also studies JFET devices for high-pressure and gives the relevant research information.