High-Efficiency High-Bandwidth Four-Quadrant Fully Digitally Controlled GaN-Based Tracking Power Supply System for Linear Power Amplifiers

The ever-rising demands for a high efficiency and high power density in the power electronics market are motivating an intensive research in the area of wide bandgap (WBG) devices, with enhancement-mode gallium-nitride (GaN) highelectron-mobility transistors as the main representatives. Compared to the conventional silicon devices with the same voltage rating and ON-state resistance, the parasitic capacitances of GaN transistors are smaller up to 10 times. Although their turn-off energy is very small, for the high switching speeds, zero-voltage switching is preferable to avoid the turn-on power losses, especially in the application where the devices operate at megahertz switching frequencies and where the blocking voltages are high. This is also very important from the thermal point of view, due to the poor junction to ambient thermal impedance of the packaging, in order to avoid high junction temperatures. Moreover, for a successful design of a power converter, the magnetic materials optimized for the high-frequency range are a must, with a manganese-zinc ferrites as the most promising solution. In this paper, an 8-W, 1-MHz switching frequency fully digitally controllable bipolar tracking power supply with a 100-kHz small-signal bandwidth, the tracking speeds up to 2 V/μs, and the maximum efficiency beyond 94% is shown, where a symbiosis of WBG devices and the newest generation high-frequency magnetic materials manifests the clear benefits.