Enhanced Power Conversion Capability of Class-E Power Amplifiers With GaN HEMT Based on Cross-Quadrant Operation

Class-E power amplifiers are widely used in megahertz frequency power conversion systems due to their high efficiency, which can further be enhanced by virtue of wide-bandgap devices such as GaN high-electron-mobility transistors. Here, a GaN-based cross-quadrant mode Class-E amplifier is proposed, which addresses one of the major challenges for such amplifiers, i.e., to achieve both high power and high efficiency with low-voltage-rating devices. By utilizing the reverse conduction of GaN transistors, a cross-quadrant mode Class-E amplifier with small dc-feed inductance is constructed, whose circuit model is derived by virtue of the Laplace transform technique. We demonstrate an experimental prototype operating at 3.11 MHz with a 100-V GaN transistor, achieving an output power of about 6 W with the efficiency being almost 90% when the input voltage is 10 V and the load resistance is 28
$\mathrm{\Omega }$
. Compared with conventional Class-E amplifiers, the power conversion capability of the proposed amplifier is increased up to three times from 0.49 to 1.69 with a slight reduction in efficiency. Such cross-quadrant mode amplifiers can be used to improve the power conversion capability and to reduce the peak switch voltage at the same output power level.