LED驱动芯片中软启动电路设计与仿真验证

Design and verification of a soft start circuit in LED driver

基于LED驱动芯片设计了一种软启动电路,应用于DC-DC转换器中,防止在芯片启动瞬间浪涌电流的产生,从而导致芯片损坏。整体电路主要由带隙基准电路、偏置电流产生电路、电容倍增电路、比较器以及由与非门构成的RS触发器组成。该电路针对传统软启动电路所占版图面积大、结构复杂等缺点,利用电流模式电容倍增电路结构应用于软启动电路中,使芯片面积显著减小。该软启动电路是在中芯国际0.18μm BCD工艺条件下进行设计和仿真验证。结果表明:软启动输出信号随时间逐步上升,并在3 ms左右完成了软启动工作。该软启动电路结构简单,易于实现,可应用于其它DC-DC转换器芯片,极具市场应用价值。

Based on the LED driver chip,a soft start circuit,whose main function is to prevent the generation of inrush current at the moment of chip start-up in the DC-DC converter,is designed.The overall circuit mainly consists of a bandgap reference circuit,a bias current generation circuit,a capacitor multiplication circuit,a comparator,and an RS flip-flop possessing an AND gate.In view of the shortcomings of the traditional soft-start circuit such as large layout area and complex structure,the current-mode capacitor multiplication circuit structure is used in the soft-start circuit to significantly reduce the chip area.The soft-start circuit is designed and verified under SMIC′s 0.18 μm BCD process conditions.The results show that the soft-start output signal gradually rises with time,and the soft-start work is completed in about 3ms.The soft-start circuit has a simple structure and is easy to implement,which can be applied to other DC-DC converter chips and has great application potential.