Low cost precision Vds sensing

Abstract

Vds current sensing has the potential to improve power density, efficiency, and cost compared to conventional current sensing methods by removing the need for a dedicated (quasi-)lossy sensing device. However, achieving high precision requires a temperature compensation method that has traditionally come at the expense of flexibility, test cost, or power density. This work proposes an online calibration method based on small signal resistance measurement through the periodic injection of small submicrosecond current pulses that are orthogonal to the load current. This provides an estimate of the large signal resistance that is insensitive to manufacturing tolerance and device type. Furthermore, junction temperature can be simultaneously estimated from the resistance variation. With 129mW injection power, the method achieves 0.54A RMS single point calibrated current error over a ±54A range on a 48V single phase experimental platform. Since all circuitry is connected parallel to the power stage, the method is suited to integration into a smart gate driver IC.