COSS Losses in 600 V GaN Power Semiconductors in Soft-Switched, High- and Very-High-Frequency Power Converters

By G. Zulauf, Sanghyeon Park, Wei Liang, K. Surakitbovorn, J. Rivas-Davila. IEEE transactions on power electronics, 2018

167 citations recorded by the source corpus.

We report losses from charging and discharging the parasitic output capacitor, <inline-formula> <tex-math notation="LaTeX">${\rm C}_{\rm OSS}$</tex-math></inline-formula>, in Gallium Nitride (GaN) power devices with voltage ratings over 600 <inline-formula><tex-math notation="LaTeX">${\rm V}_{\rm DS}$</tex-math></inline-formula> . These losses are of particular importance in soft-switched circuits used at MHz switching frequencies, where the output capacitance of the device is charged and discharged once per switching cycle during the device's off-time. This process is assumed lossless. We measure <inline-formula><tex-math notation="LaTeX">${\rm C}_{\rm OSS}$</tex-math> </inline-formula> losses from 5–35 MHz sine, square, and Class-<inline-formula><tex-math notation="LaTeX"> $\Phi _{2}$</tex-math></inline-formula> waveshapes in enhancement-mode and cascode devices, and find that losses are present in all tested devices, equal or greater than conduction losses at MHz frequencies, and exponentially increasing with <inline-formula><tex-math notation="LaTeX">$\mathbf{dV/dt}$</tex-math></inline-formula>. The cascode device outperforms the e-mode devices under 300 V, but the e-mode devices are preferred above this operating voltage. Furthermore, we show that, within a device family, losses scale linearly with output energy storage. Packaging appears to have only a minor effect on these losses. Finally, we demonstrate 10 MHz, 200 W dc–dc converters with varying device configurations, showing that, even with constant circulating currents, moving to larger devices with lower <inline-formula><tex-math notation="LaTeX">${\rm R}_{\rm DS,ON}$</tex-math> </inline-formula> actually degrades efficiency in certain applications due to <inline-formula> <tex-math notation="LaTeX">${\rm C}_{\rm OSS}$</tex-math></inline-formula> losses. In the high-voltage, high-frequency range, these reported losses must be optimized simultaneously with conduction losses on a per-application basis.

Subfields: Condensed Matter Physics, Electrical and Electronic Engineering

View Paper: https://www.semanticscholar.org/paper/788829e2da4cd9f6276bad6b4984899024456ddd