An accurate average inductor current limit method for peak current mode buck DC-DC converters

Abstract

An accurate programmable average inductor current limit method for buck DC-DC converters with peak current mode (PCM) control is presented. A Gm-C filter is used to sense the voltage drop across a current sensing resistor in series with the inductor. Then, the voltage drop is converted into a current signal by a voltage-to-current (V2I) converter. The converted current signal is superposed on the output of the error amplifier to adjust the peak inductor current. The buck converter has been designed with 0.18 µm BCD process. The current limit value is designed 1 A/2 A for the sensing resistor of 50 mΩ/25 mΩ, respectively. When the the equivalent load resistance steps from 10 Ω to 2.5 Ω/1.67 Ω, the simulation results show that the average inductor current increases from 500 mA to 0.9 A/1.8 A for the sensing resistor of 50 mΩ/25 mΩ, respectively.