Abstract
The Class $\Phi _\text{2}$ /EF $_{\text{2}}$ amplifier is an attractive topology for high-voltage and high-frequency power conversion because of the high efficiency, reduced device voltage stress, simplicity of gate driving, and load-independent ZVS operation. Due to many degrees of freedom for tuning, previous studies can only solve the single-ended $\Phi _\text{2}$ circuit using numerical methods. This work focuses on improving the design and operating characteristics of a push–pull $\Phi _\text{2}$ amplifier with a $T$ network connected between the switch nodes, or a PPT $\Phi _\text{2}$ amplifier. The PPT $\Phi _\text{2}$ amplifier has less circulating energy and achieves higher cutoff frequency $f_{T}$ than other $\Phi _\text{2}$ /EF $_{2}$ circuits. We, then, present a series-stacked input configuration to reduce the switch voltage stress and improve the efficiency and power density. A compact 6.78-MHz, 100-V, 300-W prototype converter is demonstrated that uses low-cost Si devices and achieves 96% peak total efficiency and maintains above 94.5% drain efficiency across a wide range of voltage and power. Together with the advances in wide-bandgap semiconductors and magnetic materials, the PPT $\Phi _\text{2}$ circuit opens more possibilities for the state-of-the-art performance of solid-state RF amplifiers in high-frequency, high-power applications, including wireless charging for electric vehicles, plasma RF drives, and nuclear magnetic resonance spectroscopy.
Highlights
P OWER amplifiers play a critical role in many systems that support our modern infrastructure, ranging from cellphones and radio towers to medical equipment like magnetic resonance imaging and particle accelerator for scientific research purposes
With proper tuning only on the first, second, and third voltage harmonics, the Φ2 amplifier can adequately shape a quasi-square wave drain voltage that is similar to the waveform in a Class Φ, F, or D amplifier
We show that a Push–Pull Φ2 amplifier structure with a T-network connected between the switch nodes, which we call a PPT Φ2 amplifier, can preserve all the abovementioned features while reducing the circulating energy and improving the achievable drain efficiencies compared to a single-phase Φ2
Summary
P OWER amplifiers play a critical role in many systems that support our modern infrastructure, ranging from cellphones and radio towers to medical equipment like magnetic resonance imaging and particle accelerator for scientific research purposes. With proper tuning only on the first, second, and third voltage harmonics, the Φ2 amplifier can adequately shape a quasi-square wave drain voltage that is similar to the waveform in a Class Φ, F, or D amplifier This concept is fundamentally similar to Class EF2 [9], [10], with the primary difference that most work on the Class EF2 uses a choke input inductor for L1, whereas a Φ2 inverter [8] uses a small-value resonant inductor, which improves the transient response and maximum achievable frequency.
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