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为了解决LED恒流驱动输出电流不稳的问题,提出采用双反馈环路的通道结构。在此基础上,设计了采用分段模式的快速启动电路,可极大地提升通道的开启速度。基于0.25μmBCD工艺,完成HSPICE仿真。结果显示,该系统的外环路增益为83dB,相位裕度为80o,通道间电流互不影响。当电流在5～45mA范围内变化时,快速启动电路正常工作,通道的开启时间仅为4ns,开启速度较传统结构有显著提升。该输出通道已成功应用于LED恒流驱动中。
In order to solve the problem that the LED constant current drives the output current instability, a channel structure adopting a double feedback loop is proposed. On this basis, the fast start-up circuit using the segmented mode is designed, which can greatly improve the opening speed of the channel. Based on 0.25μm BCD process, complete HSPICE simulation. The results show that the outer loop gain of this system is 83dB, and the phase margin is 80o. The currents between channels do not affect each other. When the current changes in the range of 5 ~ 45mA, the fast start circuit works normally, the opening time of the channel is only 4ns, the opening speed is significantly improved compared with the traditional structure. The output channel has been successfully applied to LED constant current drive.