Extending Current Shunt Bandwidth for Accurate Switching Loss Evaluation of Wide-Bandgap Devices

Dominated by the zero formed by current shunt resistance and equivalent series inductance, the bandwidth of low-resistance current shunt is difficult to improve, which impedes accurate switching loss evaluation of latest wide-bandgap devices with higher current rating and faster switching speed. The article provides an unconventional Wheatstone-bridge viewpoint of the shunt model, revealing an “infinite bandwidth” condition. Based on the condition, a novel “single-L” compensator is proposed, effectively expanding the bandwidth of a 15 mΩ commercial shunt from 20 to 587 MHz. Also, two customized low-cost PCB shunts targeting at natural “infinite bandwidth” are also proposed, realizing 910 MHz/15 mΩ bandwidth which is seven times higher than the state-of-the-art design. All methods are verified via experiments. The proposed methods demonstrate a strong reduction in the error of switching loss calculation during double pulse test, leading to only 9% and 3% deviation in
E
_off
and
E
_on
characterization which is much better than the 55% and 31% error caused by low-bandwidth commercial shunt.