A 2.3 mW 1 MHz digitally isolated hysteretic current control circuit with shunt-based current sense amplifier

Hysteretic current control (HCC) of the inductor current in switched-mode power converters enables fast and direct control and requires high bandwidth isolated current sensing. However, analog-isolated Hall or TMR sensors consume a high power (typ.: 15mW at 1.5MHz). This work presents a digitally isolated HCC circuit using a shunt resistor, differential amplifier and two comparators with selectable reference values. A 1 MHz bandwidth HCC circuit was built and applied to a half-bridge converter, consuming only 2.3mW during operation (from which 1mW are from an isolated 5V power supply).