Abstract:An Light Emitting Diode(LED) constant current drive circuit with the over-temperature protection and the adaptive temperature regulation is designed. The drive circuit is mainly composed of an over-temperature protection circuit and an adaptive circuit. The over-temperature protection circuit is utilized to detect the operating temperature of the system. When the system is under high temperature, the shutdown signal is output to stop the circuit. The adaptive temperature adjust circuit would input Proportional To Absolute Temperature(PTAT) current to the constant current module to adjust the LED drive current, then the adaptive regulation is achieved. The circuit, combining the temperature adaptive regulation with the hysteresis function of the over-temperature shutdown circuit, is simple, but with high performance. Based on the 0.5 μm CMOS process, Specter simulation results show that when the system temperature changes from 0 ℃ to 89.6 ℃, the constant current output fluctuation is less than 0.57%. when the change is from 89.6 ℃ to 111 ℃, the adjustable output current is 80 mA. When the temperature rises up to 114 ℃, the over-temperature protection circuit is switched on, and the circuit stops working. When the temperature drops back to 73.3 ℃, the LED drives circuit to start work again.