具有边界限制的线性折返式电流限产生电路

A Linear Fold-Back Current-Limit Generator with Boundary Limitation

提出了一种随温度折返式变化的电流限产生电路。该电路能起到系统级过温保护的作用。采用NTC热敏电阻来采样温度的变化信息,再放大后转换成电流,以便动态并线性地控制电流限。利用内嵌的多环路控制策略,动态引入边界限制调整环路,实现电流限的上限和下限箝位。基于标准0.35μm CMOS工艺,对折返式电流限电路进行了实现与验证。仿真结果表明,当NTC热敏电阻上的电压大于500mV或小于350mV时,电流限设置电压分别维持在500mV(上限)和250mV(下限);当NTC热敏电阻上的电压在350~500mV之间变化时,电流限电压会在上限与下限值之间随温度线性变化,变化率为1.67mV/mV。

A fold-back current-limit generator changing with temperature was proposed,which played the role of system-level over-temperature protection.The circuit used the NTC（Negative Temperature Coefficient）thermistor to sample the temperature changing information which was then amplified and converted into current to control the current-limit dynamically and linearly.By using the embedded multi-loop control strategy and dynamically introducing the boundary limit adjustment loop,it was possible to clamp the upper-limit and lower-limit of the current-limit.The proposed circuit was implemented and verified in a standard 0.35 μm CMOS process.The simulation results showed that the current-limit was maintained at 500 mV（upper-limit）or 250 mV（lower-limit）when the voltage on the NTC thermistor was more than 500 mV or less than 350 mV.When the voltage on the NTC thermistor varied between 350 mV and 500 mV,the current-limit voltage would vary linearly with temperature between the upper-limit and lower-limit at a changing rate of 1.67 mV/mV.