Implementation and Design of Current-mode PWM Control CMOS Buck Power Converter with Protection Circuits

A lower power consumption, smaller output ripple and better regulation current-mode CMOS buck power converter with a novel on-chip soft-start circuit for feedback control is implemented in this paper. The over-current protection and soft-start circuit can produce a slowly rising output voltage without extra clock or any external component to prevent inrush current and output voltage overshoot during the start-up period of the converter. The converter is designed and simulated using the TSMC 0.18 mu m MM/RF 1P6M SALICIDE 1.8V/3.3V CMOS process. Hspice simulation results show that, the buck converter having 1.129 x 1.200mm(2) chip size with power efficiency about 90%. This chip can operate with input supply voltage from 2.8V to 3.3V, and its output voltage can stable at 1.2V and less than 22mV ripple voltage at maximum loading current 500mA. The simulation shows the circuit has about 1.0ms of soft-start time and can inhibit the inrush current when the power on.