一种适用于LDO的无过冲软启动电路设计

A non-overshoot soft-start circuit design for LDO

设计了一种适用于LDO的无过冲软启动电路。其核心是采用线性升压的软启动策略来消除浪涌电流,电路结构简单、易于实现。为了解决超调现象,利用晶体管与正反馈电路设计了一种快速比较器,使得软启动电路输出电压能平滑地过渡到稳定工作状态。为了减小版图面积,利用少量的MOS管设计了斜坡产生电路和输入不平衡比较器电路。该软启动电路集成到一款低压差线性稳压器中,采用SMIC 0.18μm BCD工艺实现,电源电压为4.5 V。仿真结果表明,软启动电路有效地消除了浪涌电流,实现输出电压平稳上升无过冲,并能平滑地过渡到稳定工作状态,无超调现象产生。电路结构简单,版图面积为98μm×60μm,便于片上集成,该电路也可以应用到一般的DC-DC稳压器中。

A non-overshoot soft-start circuit for LDO was designed.The core of the circuit is to eliminate the inrush current by using the soft start strategy of linear boost.The circuit structure is simple and easy to implement.In order to solve the overshoot phenomenon,a fast comparator was designed by using the transistor and positive feedback circuit,so that the output voltage of the soft start circuit can smoothly transited to a stable working state.In order to reduce the layout area,a ramp generation circuit and an input imbalance comparator circuit were designed using a small number of MOS transistors.The soft-start circuit was integrated into a low dropout linear regulator,which was implemented in SMIC 0.18μm BCD process,and the power supply voltage was 4.5 V.The simulation results show that the surge current is effectively eliminated by the softstart circuit,the steady rise of the output voltage without overshoot and smooth transition to the stable working state without overshoot are realized.The circuit structure is simple,and the layout area is 98μm×60μm,which is convenient for the onchip integration.The circuit can also be applied to general DC-DC regulators.