Investigation of Trade-Off between Sensor Bandwidth and Damping Achievable Through a Rogowski Coil Based Current Sensor

High bandwidth current sensors are required to capture high frequency switching currents in power devices. In addition to their high bandwidth, rogowski coil based current sensors can be integrated with the power converter PCB. The coil is fabricated near the device terminals and may therefore cause an increase in the commutation cell inductance. This increased commutation cell inductance may exacerbate switching ringing as well as the EMI generated by the device. This paper presents a method to damp out switching ringing through resonant coupling of commutation circuit with the rogowski coil. The effect of this coupling on the signal processing circuitry of rogwoski coil is presented subsequently. It is shown with simulation results that the bandwidth of current sensor is limited when the rogowski coil is tuned for resonant damping. Therefore a trade-off between the requisite damping and sensor bandwidth can be established by weighing in the converter design requirements viz. the EMI generated and current sensor performance.