Contactless Current Sensing with Bandwidth Enhancement for High-Frequency Power Converters

High-frequency power converters are gaining increasing attention and popularity due to the high power density and high efficiency demand in electric vehicles. In this condition, high-frequency current sensing accuracy is essential. However, existing current sensing methods cannot meet the needs in terms of low power loss, small size, being contactless, or large bandwidth. This paper proposes a new current sensing technique with bandwidth enhancement. First, a skin effect model for commonly used rectangular conductors is investigated. Then, variations of out-of-plane and in-plane magnetic fields caused by skin effect are analysed theoretically. It reveals that measuring out-of-plane magnetic fields shows a larger bandwidth than measuring in-plane magnetic fields. Subsequently, a circle trace for current sensing is proposed. The corresponding simulation results illustrate necessary considerations in a circle trace-based PCB design. Then, the current responses of a proposed circle trace and a conventional straight trace are compared in experiments. In experiments, the step current response has an average improvement of 48%, and the measurement bandwidth is extended from 10 kHz to 200 kHz using the circle trace method. These experimental results confirm that the circle trace shows better performances. Thus, the proposed method is validated for application in high-frequency current sensing.