一种高精度滞环控制恒流LED驱动电路

A High Precision Constant Current LED Driving Circuit with Hysteresis Control

基于降压型结构,设计了一种高精度的恒流LED驱动电路。在滞环控制模式的基础上,采用一种新型的自适应关断时间控制环路替代谷值检测反馈环路,间接地实现了对电感电流谷值的精确控制,避免了对谷值直接采样所带来的误差,提升了系统的恒流精度。控制环路采用低边采样方式,降低了采样电阻上的损耗,提升了系统的转换效率。该LED驱动电路基于TSMC 0.18μm 70 V BCD工艺进行了仿真与设计。结果表明,在20~125 mA负载电流范围内,最大恒流误差不超过0.8%。在20~100 V输出电压范围内,平均电流变化率小于1%。

A high precision constant current LED driver based on buck topology was presented. Based on the hysteresis control mode, a new type of adaptive off-time control loop was adopted in this circuit instead of valley detection feedback loop, which indirectly achieved accurate control of the inductor valley current. Therefore, the error caused by direct sampling of the valley current was avoided, and the constant current accuracy of the system was improved. The low-side sampling was adopted to this loop to reduce the loss on the sampling resistor which improved the conversion efficiency of the system. The LED driving circuit had been designed and simulated in TSMC 0.18 μm 70 V BCD process. The simulation results showed that the maximum constant current error was not more than 0.8% within the range of 20~125 mA load current. The average current change rate was less than 1% within the range of 20~100 V output voltage.