In this work an easy to integrate and low-cost solution for an overcurrent detection in high-current, paralleled 100 V, 7 mΩ GaN HEMTs is presented. The overcurrent detection is realized with a simple pickup-coil which is integrated into the carrier PCB adjacent to the GaN transistors. The pickup-coils have a sensitivity of around 12 mV/A, which results in a peak voltage of above 1.5 V at 111 A switched current and is twice as high as the peak voltage at the rated current of 50 A per HEMT. A simple signal evaluation circuit based on a differential integrator and a fast comparator is presented, which allows a very fast and reliable detection of overcurrent events in below 30 ns. The presented pickup coil has a significantly increased sensitivity to parasitic effects and coupling due to the high bandwidth of above 400 MHz, but offers a very simple implementation and the advantages of a non-invasive measurement and scalability for higher voltage classes.
