Comparison of Radio-Frequency Power Architectures for Plasma Generation

Applications such as plasma generation require the generation and delivery of radio-frequency (rf) power into widely-varying loads while simultaneously demanding high accuracy and speed in controlling the output power across a wide range of power levels. Attaining high efficiency and performance across all operating conditions while meeting these system requirements is challenging, especially at high frequencies (10s of MHz) and power levels (1000s of Watts and above). This paper evaluates different architectures that directly address these challenges and enable efficient high-frequency operation over a wide range of output power levels and load impedances with the capability of fast output power control (e.g., within a few microseconds). We review techniques for achieving fast output power control and evaluate their suitability in efficient rf systems demanding accurate and fast control of output power. Two dc-to-rf system architectures utilizing the discussed power control techniques are presented to illustrate both the achievable performance benefits as well as their robustness to load impedance variation, and are compared using time-domain simulations. The results indicate the ability of the proposed architectures to maintain high efficiency (> 90%) across a very wide range of output power levels (e.g., over a factor of up to 85x) while being robust to load impedance variations.