IEEE Transactions on Transportation Electrification ( IF 5.444 ) Pub Date : 2020-04-20 , DOI: 10.1109/tte.2020.2989036
Ruoyu Hou; Yanfeng Shen; Hui Zhao; Hao Hu; Juncheng Lu; Teng Long

Gallium nitride enhancement-mode high electron mobility transistors (GaN E-HEMTs) can achieve high frequency and high efficiency due to its excellent switching performance compared with conventional Si transistors. Nevertheless, GaN HEMTs exhibit a more pronounced dynamic ON-state resistance $R_{\mathrm {DS}(\mathrm{\scriptscriptstyle ON})}$ than silicon transistors. The variation of $R_{\mathrm {DS}(\mathrm{\scriptscriptstyle ON})}$ is caused by both the static $R_{\mathrm {DS}(\mathrm{\scriptscriptstyle ON})}$ due to junction temperature rise and the dynamic $R_{\mathrm {DS}(\mathrm{\scriptscriptstyle ON})}$ due to the electron trapping. Without a careful decoupling analysis, it is difficult to calculate and model the dynamic $R_{\mathrm {DS}(\mathrm{\scriptscriptstyle ON})}$ portion. This article introduces a comprehensive approach of dynamic $R_{\mathrm {DS}(\mathrm{\scriptscriptstyle ON})}$ evaluation comprising four techniques: 1) a clamping circuit for both the hard-switching (HS) device and synchronous rectification (SR) device; 2) a junction temperature monitoring technique; 3) control of both the pulse test and soak time; and 4) continuous operation of device under test. Based on the dynamic $R_{\mathrm {DS}(\mathrm{\scriptscriptstyle ON})}$ test results, a new model of the $R_{\mathrm {DS}(\mathrm{\scriptscriptstyle ON})}$ variation is developed where two coefficients $k_{T{j}}$ and $k_{\mathrm {dR}}$ are defined to model the contribution of the heating effect and the impact of the trapping effect, respectively. The $R_{\mathrm {DS}(\mathrm{\scriptscriptstyle ON})}$ model is validated by the comparison between the calculated and measured junction temperatures of a 650-V/30-A GaN-based half-bridge. Furthermore, a detailed loss breakdown analysis is conducted for the GaN-based HS half-bridge. The results show that the switching losses, $E_{\mathrm{\scriptscriptstyle ON}}$ and $E_{\mathrm{\scriptscriptstyle OFF}}$ , are the dominant loss factors with high switching frequency. At last, the possible efficiency improvements are also discussed in detail.

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