一种DC-DC开关电源片上软启动电路

提出了一种基于DAC(digital-to-analog converter)控制的数字软启动电路,利用DAC控制和软启动电压检测技术,有效抑制了DC-DC开关电源启动过程中产生的浪涌电流和输出电压过冲,实现了输出电压从零到调整值的平坦上升.在启动完成后启动电路的偏置电流被彻底关断,实现了低功耗没计.该软启动电路采用CMOS器件设计,无需任何外围元件,便于被DC-DC开关电源集成.该电路已成功集成到一款Buck型PWM(pulse width modulation)控制器当中,测试结果表明:在整个负载范围内,DC-DC在启动过程中电感电流平稳变化,输出电压平滑上升、无过冲,启动时间控制在1.2ms.

An On-Chip Soft-Start Circuit for DC-DC Switching Regulators

A soft-start circuit based on DAC (digital-to-analog converter) control for DC-DC switching regulator is presented.Using the techniques of DAC control and soft-start voltage sense,the rush current and overshoot of the output voltage during start-up are eliminated effectively,allowing for a smooth output voltage ramp from zero to regulation.At the end of start-up,the biased current of the soft-start circuit is cut off completely. Consequently,it is power-efficient.The circuit is designed using CMOS devices without the need of any external components,so it is suitable for integration in DC-DC switching regulators.The proposed soft-start circuit has been applied to a Buck PWM controller successfully.The experimental results show that in the entire load range the output of the system can start up smoothly,the inductor current remains stable,the output voltage rises smoothly without overshot,and the soft-start time is about 1.2ms.