Xingyue Tian

High-power transient voltage suppression (TVS) diodes serve as the primary energy-absorbing elements in solid-state circuit breakers (SSCBs), providing rapid clamping of over voltages that threaten main interrupting devices. This paper presents a coaxial packaging solution for stacked TVS diodes, which achieves a dramatic reduction in commutation loop inductance from 95 nH to 3.8 nH, resulting in an approximately 96% reduction. Experimental validation, which demonstrates a substantial decrease in turn-off overvoltage from 950 V to 300 V, shows an approximate 68% reduction. A derived modular design is further proposed to achieve higher voltage ratings, enabling scalable deployment across different SSCB applications. The package performance is evaluated through finite element analysis (FEA) of inductance and electric field distribution and experimentally confirmed in a 1.7 kV/100 A SSCB. Results verify that the proposed coaxial package effectively mitigates loop inductance and overvoltage, enhancing both reliability and operational safety of high-power SSCBs.

Accurately measuring the switching current behavior of wide bandgap devices requires a current sensor with a wide bandwidth covering dc to high frequency ranges. However, traditional Rogowski coils (RCs) for current sensing either lack the dc measurement capability or the inclusion of dc sensor largely increases the insertion inductance. This article presents a concept of combining a shielded RC with a dc sensor to improve the dc measurement capability without interfering with the power loop area of a double pulse test (DPT) circuit. The RC and dc sensor are positioned at different locations to capture the high-frequency and low-frequency components, respectively. An analog circuit combines the output of both sensors to recreate the signal. Frequency domain analysis of the prototype confirms the improved dc measurement of the probe. This article also presents the results of a DPT of a half-bridge SiC power module to demonstrate the enhanced dc measurement of the shielded RC, without any parasitic interference in the power loop area.

Lateral gallium nitride (GaN) high-electron-mobility transistors present better electrical characteristics compared to silicon or silicon carbide devices such as high switching speed and low gate charge, but also present additional challenges on the module design. This article discusses a high-density GaN power module with double-sided cooling, low inductance, on-package decoupling capacitors, and integrated gate drivers. The GaN dies as well as the gate drive are sandwiched between the printed circuit board and direct bonded copper substrate to achieve compact loop and double-sided cooling effect. Design considerations and thermal performance are analyzed. A module assembly procedure is presented utilizing the layer-by-layer attachment process. Finally, a 2.7 cm × 1.8 cm half-bridge GaN power module is fabricated and tested, achieving a low power-loop inductance of 1.03 nH, and the overshoot voltage of the switching waveform is less than 5% under a 400 V/25 A double-pulse test. The thermal resistance is 0.32 K/W, verified by simulation and experimental results. The design and assembly process can be generalized and applied to high power applications to achieve high power density and high performance.