Effective protection circuits used in high power step-down converter

Effective protection circuits for high power step-down converter are presented in this paper to protect the converter from damage under any fault condition. A novel built-in soft-start circuit with simple topology is implemented by controlling the input reference voltage of error amplifier to eliminate the inrush current and avoid the overshoot of the output voltage without using external capacitor, which reduces the component cost, saves board space and benefits for portable applications. Besides, an enhanced current limit strategy is proposed to guarantee the proper work of the converter in normal load, and avoid “current tail” in major overload or short circuit. The proposed circuits have been validated with 18V high-voltage CMOS process based on a monolithic voltage-mode step-down converter capable of driving up to 1A loads with supply voltage from 5 to 18V. Simulation results demonstrate that the proposed protection circuits can guarantee the step-down converter operating properly under any condition without damage.