A High-Bandwidth Resistive Current Sensing Technology for Breakers and Desaturation Protection

High switching frequencies, steeper voltage and current slopes make for challenging requirements for real time current sensing, especially due to overshoot from sensing element inductance. High-bandwidth current sensing is required to ensure safe, reliable and efficient operations and to engage protection during critical failures. This paper describes and demonstrates a high bandwidth resistive current sensing technology for solid state circuit protection and diode-less power device desaturation protection. The sensor uses mutual inductance cancellation as well as residual inductive voltage subtraction for ultra-low-overshoot transient response. Full design steps and equations are presented for scaling the design. The demonstration design is fabricated using rigid and flexible PCB technologies. Test results show a 70.5% reduction of insertion inductance for the same power dissipation and sensitivity. VNA and spectrum analyzer measurements are used to characterize the prototypes of the proposed design. The paper also discusses two applications of desaturation protection and overcurrent protection for SiC FETs.