An All-Passive Compound Current Sensor for Fast Switching Current Monitoring

In this paper, a compound current sensor suitable for fast switching current (or similar applications) measurement is presented. The compound sensor consists of two current transformers (CT) with (very) different operating working frequency bandwidth (BW) values. The outputs of each transformer are conditioned and aggregated together through an all-passive impedance network. Hence, a wideband (10Hz-10MHz) current sensor is obtained, having a gain of -20 dB or the sensitivity of 100 mV/ A without any amplification. Therefore, the proposed sensing solution requires little to no secondary active circuits compared to regular current transformers, Rogowski coils, Hall-effect sensors, etc. Having an all-passive circuitry brings certain advantages for space, aerospace, and avionic applications. The operating and design principles of the proposed sensing solution are presented. Furthermore, an analysis of the gain, accuracy, and consistency of the proposed sensor in a switching converter is provided to confirm the validity of the proposed passive topology.