High-Efficiency, Low Voltage Stress Power Amplifier with Push-Pull Wave-Shaping Operation

Researchers in the Stanford University Power Electronics Research Lab have designed an easy to implement, high-efficiency, high-frequency power amplifier with low voltage stress. The design uses a combination of circuit stages operating out of phase to provide push-pull operation; a switching circuit and impedance path to drive the circuit; and a waveform-shaping circuit to shape the voltage for presentation to the switching circuit. The SUPER Lab high efficiency amplifier prototype produces higher power than a conventional Class E circuit, reduces voltage stress, has low circulating energy, reduced filtering requirements, and load-independent Zero Voltage Switching operation, making it particularly attractive for energy hungry, high-voltage and high-frequency radiofrequency and microwave applications (e.g. RF plasma generators, cellphone antenna, MRI resonators), wireless charging and more.

Stage of Development – Prototype
The SUPER Lab built and tested a 6.78-MHz 300-W series stacked push–pull ?2 amplifier with a T-network ("PPT ?2" amplifier prototype figure 1) that reached 96% peak total efficiency and high efficiency across a wide range of voltage and power (figure 2). Future performance improvement plans include incorporating recent innovations in wide bandgap (WBG) power semiconductors. Using this amplifier topology, the SUPERLab built and tested a 6.78-MHz 1.7-kW wireless charging system that reached a 95.7% dc-dc efficiency for an electric car, with an ongoing effort of pushing the power beyond 5 kW.