Highly Efficient and Compact GaN-Based Tracking Power Supply System for Linear Power Amplifiers

Linear power amplifiers (LPA) are the preferred option in industrial applications whenever an excellent linearity, low noise operation and good stability margin are needed. The power losses of a LPA can be significantly reduced by employing switched-mode power converters to modulate its supply rails. Regarding the power devices, for a more compact solutions Enhancement-mode Gallium-Nitride High-electron-mobility Transistors (GaN E-HEMTs) are the better choice compared to the conventional Silicon (Si) devices with the same voltage rating and on-state resistance since the parasitic capacitances of GaN transistors are lower up to 10 times. Although their turn-off energy is very small, for the high switching speeds Zero-Voltage Switching (ZVS) is preferable to avoid the turn-on power losses, especially in the application where the devices operate at MHz switching frequencies and where the blocking voltages are relatively high. In this paper, an 8 W, 1 MHz switching frequency, with 80 V of output voltage swing, fully digitally controllable bipolar tracking power supply (TPS) is shown. The designed small signal bandwidth is 100 kHz and the tracking speeds reach up to 2 V/μs. The maximum efficiency of the TPS is beyond 94 % while the power stage of the TPS occupies less than 10 cm
²
.