Optimal Control of a High Frequency Class-D Amplifier

Dahl N, Iversen N, Knott A, Andersen MAE. Optimal Control of a High Frequency Class-D Amplifier. J Audio Eng Soc. 2018;66(1/2):34-43. doi:10.17743/jaes.2017.0046

@article{Dahl2018_19374,
  author = {Dahl, Nicolai and Iversen, Niels and Knott, Arnold and Andersen, Michael A. E.},
  title = {{Optimal Control of a High Frequency Class-D Amplifier}},
  journal = {Journal of the Audio Engineering Society},
  volume = {66},
  number = {1/2},
  pages = {34--43},
  year = {2018},
  month = jan,
  publisher = {Audio Engineering Society},
  doi = {10.17743/jaes.2017.0046},
  url = {https://doi.org/10.17743/jaes.2017.0046}
}

TY  - JOUR
TI  - Optimal Control of a High Frequency Class-D Amplifier
AU  - Dahl, Nicolai
AU  - Iversen, Niels
AU  - Knott, Arnold
AU  - Andersen, Michael A. E.
T2  - Journal of the Audio Engineering Society
J2  - J. Audio Eng. Soc.
VL  - 66
IS  - 1/2
SP  - 34
EP  - 43
PY  - 2018
DA  - 2018/01/06
DO  - 10.17743/jaes.2017.0046
UR  - https://doi.org/10.17743/jaes.2017.0046
PB  - Audio Engineering Society
LA  - en
AB  - During the last decade, switch-mode audio amplifiers have become a common choice for audio applications because of efficiencies approaching 90% and distortions as low as 0.001%. Such amplifiers modulate the input audio into a high-frequency discrete signal that drives a Class-D power stage. The control loop is the key element in achieving high-quality performance. Modern control theory methods were used to design and simulate a full-state feedback integrating controller for use with a high-frequency bridge class-D amplifier. An optimal linear full-state integral controller based on the state-space model was designed using the Linear Quadratic Regulator (LQR) method, and verified on a linear and switching model. Measurements on a Class-D amplifier with the implemented controller showed that the step responses and THD+N measurements were aligned with theoretic predictions. A 30-fold reduction in THD+N was observed compared to open-loop. The results prove that the principals of modern control achieve good performance in Class-D amplifiers, even when the output filter has a large resonance.
ER  -