Noise-Immune Current Sensor Using a Shunt Resistor

This paper introduces a differential current-sensing architecture that uses a shunt resistor to enhance noise immunity in peak current-mode control switching converters. Conventional single-ended structures are sensitive to common-mode noise due to PCB parasitic impedance and high di/dt switching transitions, causing gain errors, nonlinearity, and false triggering. The proposed architecture independently extracts both nodes of the shunt resistor and processes the signals differentially. Low-pass filtering is employed to suppress switching spikes, while a folded-cascode amplifier with cascode current mirrors offers high gain and accurate current replication. Simulations under ideal conditions, parasitic inductance, and combined parasitic-plus-noise conditions confirm that the proposed structure maintains a gain close to the designed value of 11. Results indicate substantially improved linearity and output accuracy compared with single-ended sensing, making the proposed architecture suitable for high-speed switching environments.