Design Guidelines for Shield-Less PCB-Based Rogowski Coil Sensors With Passive Offset Compensation for Switching Current Measurement

PCB-embedded coil realization is particularly suitable for ultrafast current sensing, due to its di/dt detecting principle and ease of integration into power converters. In one possible implementation, a Rogowski coil current sensor is utilized to measure switching currents, since there is no theoretical limit to its coil's magnetic saturation. There are, however, some challenges associated with existing EMI emission, dV/dt coupling, and bandwidth difference that often complicate the design of circuits and the choice of appropriate electronic components. A number of solutions have been proposed to overcome those issues, including shielding, differential-coil/integrator type circuitry, as well as ground decoupling. The sensing bandwidth of the coil, however, is limited by solutions such as shielding. The purpose of this paper is to provide practical design considerations in respect to coil and its termination, integrator types, compensation methods, and layout guidelines for the development of shield-less Rogowski coil switch-current sensors that are capable of delivering an extremely accurate and clean ultrafast signal, where they are expected to provide higher accuracy and faster response time than existing current sensing solutions. The paper will also discuss the effects of parasitic elements on the sensor's accuracy. In order to validate the sensor prototypes, switching node current experiments are conducted using a SiC power module.