A novel current-limit strategy used in high power step-down converter

摘要

A novel current-limit strategy suitable for high power step-down converter is presented in this paper to ensure the converter far away damage under over-current or short-circuit conditions. The proposed circuit consists of two sections: error amplifier clamping (EAC) and linear frequency fold-back (LFFB). The EAC circuit works properly when the output is in minor overload. If the current increases continuously to some amount in major overload or short-circuit, the frequency of the converter is linearly decreased by the LFFB circuit. In this way, the propagation delay effects can be weakened by equivalently decreasing duty cycle. The proposed circuit has been validated in 0.6-μm CD process based on a monolithic current-mode step-down converter capable of driving up to 3A loads with supply voltage from 4.5 to 23V. Simulation results demonstrate that the proposed current-limit technique can guarantee the converter operating properly under any load condition without damage.