带过温保护功能的LED恒流驱动电路设计

Design of constant current LED driver circuit with thermal-shutdown function

本文设计了一种带过温保护功能的LED恒流驱动电路。该电路由恒流驱动模块和温度传感模块组成,能在设定温度下同时控制两个开关NMOS管,实现过温保护功能。恒流驱动模块采用的方案能够有效降低恒流工作电压并实现利用外接电阻控制恒流输出的大小,驱动电流范围为54.26mA到258.24mA。当驱动电流为258.24mA时,恒流工作电压仅为0.35V。在LED电源电压正负变化10%范围内,驱动电流变化小于5%。温度传感模块利用PTAT（与绝对温度成正比）电压与基准电压比较,产生关断信号,关断温度在60℃~100℃范围内可由外接电阻设定。

Constant current LED driver circuit with Thermal-Shutdown Function was designed.It consists of constant-current driver module and temperature-sensor module.The circuit can turn off two MOSFET at one time,when the chip’s temperature is higher than the setting temperature.Co-nstant-current driving circuit can effectively reduce the operating voltage and control the current by external resistor.The driving current range of 54.26mA to 258.24mA.The operating voltage a-chieved only 0.35V when the current was 258.24mA.The output driving current changes less than 0.5% when supply LED voltage varies ±10%.Temperature-sensor module compares the PTAT（Proportional To Absolute Temperature） voltage with reference voltage to general shutdown sign-al and turn off the circuit at setting temperature fixed by exterior resistor over the range of 60℃~100℃.