A High-Speed Current Sensing Method Based on a Nonlinear Current Divider and Optical Coupling in the NIR Spectrum

Abstract

The present article introduces a high-speed optical current-sensing method for diodes based on nonlinear current division and near-infrared light-emitting diode (LED)–photodiode coupling. In addition, a technique for the compensation of a stray inductance effect was also shown. With an experimental setup, at room temperature, 1.19% accuracy was achieved beside a temperature dependence of −0.34%/°C or better within 28 °C–60 °C. The sensor system inherently provides galvanic isolation on the contrary to shunts since the current signal is converted to and transmitted as light signal on sensor level. At the same time, our optical current sensor circuit’s demonstrated that approximately 1 MHz effective bandwidth makes it competitive with Hall cells with respect to speed. Simultaneously, its immunity to stray magnetic fields and the lack of hysteresis effects due to magnetic cores are clear advantages in comparison to the state-of-the-art Hall sensors. Overall, the new measurement method offers an optimal choice for high-voltage, high-frequency current-sensing applications prone to induced magnetic fields, like switched current measurement on the freewheeling diodes used in motor drive inverters.