Transmission Line Rogowski Coil: Isolated Current Sensor With Bandwidth Exceeding 3 GHz for Wide-Bandgap Device
Yulei Wang, Teng Long, Mingrui Zou, Peng Sun, Jiakun Gong, Liang Wang, Luke Shillaber, Frede Blaabjerg, Ke Jiang, Zheng Zeng
Abstract
Rogowski coil (RC) has been commonly employed in power electronics due to its benefits of galvanic isolation, high-current measurement capability, and simple integration. However, the bandwidth of RC is restricted to tens of megahertz because of the inextricable resonance issue caused by its self-inductance and parasitic capacitance. This limitation hinders the ability of the RC to measure fast current transients such as those of wide-bandgap (WBG) power devices. In this letter, the concept of transmission line RC (TL-RC) is proposed to address the limitations of inductance and capacitance. The design criteria of double-ended impedance matching are further derived to ensure optimal signal integrity of TL-RC at gigahertz levels. These two concepts jointly form the isolated current sensor design with a bandwidth exceeding 3 GHz. Comparative experiments confirm the ultrafast and isolated advantages of the TL-RC for the WBG applications.