一种车规级LED驱动芯片的电流检测电路

Current monitoring circuit of automotive grade LED driver

为了使车规级LED驱动芯片满足ISO 26262功能安全要求,设计一种高精度LED电流检测电路。在传统LED恒流驱动输出电流检测电路的基础上,在电流复制模块加入负反馈环路,实现了对检测电流的精确复制,避免传统电流检测电路的采样误差,提升了电流检测的准确度。同时新电路采用采样管和功率管串联结构,减小电流漏检测的情况发生,扩大了有效检测的覆盖率。该LED电流检测电路采用SMIC 0.18μm CMOS工艺进行设计,测试结果表明,在5 mA~60 mA的LED电流范围内,检测精度可达±1%。

A high precision LED current detection circuit is designed in order to meet the functional safety requirements of ISO 26262.Based on the traditional LED constant-current detection circuit,a negative feedback loop is added in the current mirror module to achieve accurate copy of the detection current,avoid the current sampling error in the traditional current detection circuit,and improve the accuracy of the current detection.At the same time,the new circuit adopts the structure of sampling block and power block in series,which reduces the occurrence of current miss detecting and expands the coverage of current detection.The LED current detection circuit is designed by SMIC 0.18μm CMOS process.The test results show that the detection accuracy can reach±1%in the range of 5 mA~60 mA LED current.