Ultra-Wideband Unidirectional Reset-Less Rogowski Coil Switch Current Sensor Topology for High-Frequency DC-DC Power Converters

Abstract

Current measurement of the semiconductor switches can provide critical analytics for protection, control, and several further applications, especially for high-frequency power electronics. Therefore, there is a requirement for a switch current measurement that can fulfill the required speed and accuracy in higher-frequency applications. Along with numerous existing switch current sensing methods, the PCB-embedded Rogowski coil switch current sensor is one of the best to be cast off for high-power compact designs of medium to high-frequency applications. This is due to their linear magnetic permeability (in PCB or air core), ultrahigh bandwidth, and easy integrability. Nevertheless, it gives a few shortcomings, such as being unable to detect DC and very low-frequency currents in principle. As the nominal switching frequency tends to exceed hundreds of kilohertz, overcoming the droop issue using electronic active reset becomes nearly impractical due to excessively short off time for discharging the integrator capacitor. This paper proposes a Rogowski coil switch current sensor topology and some of its applications, particularly overcoming the deficiency of DC and low-frequency components in switch current sensing, with no applying reset. In the proposed topology, the main idea is to add an extra analog rectified amplifier to the AC-coupled signal of the Rogowski coil to maintain the actual waveform DC value and compensate for the droop issue instantaneously. A well-tuned ultrahigh bandwidth unidirectional switch current sensor was prototyped and tested to measure the switch current for monitoring and shoot-through protection of a high-speed power SiC converter.