Overcurrent protection utilising high speed and accurate current sensing circuit for switching mode DC-DC converter

Abstract

ABSTRACTA high speed and accurate over current protection (OCP) circuit with novel current sensing circuit based on source-degeneration voltage to current converter is presented in this paper for switching mode DC-DC converters. Moreover, a reference generator circuit is designed to generate current set point to be compared with sensed current for OCP. Another four bit binary decoder is employed to control and change the current set point to achieve different levels for OCP. To reduce the fluctuations at the output of the OCP, a blanking-delay block is introduced based on Schmitt trigger topology. The OCP is designed with 130 nm CMOS process technology. Post-layout simulation results show that the OCP works well from 0.5 V to 5 V output voltage of switching mode DC-DC converter. The current sensing block achieves wide input common mode range between 0.5 V and 2.5 V with 61 degree phase margin. OCP works with 3.3 V supply voltage while consuming 600 µA at standby mode and 2 mA when triggering. Total silicon die area is 242 µm × 186 µm.