A digital-controlled soft-start circuit for negative output DC-DC converter

To suppress the inrush current and overshoot voltage generated at the start-up stage of Buck-Boost converter, a digital-controlled soft-start circuit based on digital-to-analog converter (DAC) control technology is proposed in this paper. The power consumption of the circuit is zero and the circuit is also keeps the characteristics of simple structure and high reliability. The circuit has been integrated into a Buck-Boost converter with negative voltage output by using the 0.18 mu m CDMOS high voltage process. The experimental results show that this circuit can effectively suppress the rush current, and the output voltage drops smoothly from 0 to the adjustment value, -4V.