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H. Votzi, H. Ertl, F. Himmelstoss:
"Hybrid Filter for a Multi-Cell Switch-Mode Power Amplifier";
Vortrag: International Conference on Electrical Drives and Power Electronics EDPE, Dubrovnik; 04.10.2017 - 06.10.2017; in: "EDPE", (2017), S. 112 - 117.

The paper presents a novel filtering concept for multi-cell switch-mode power amplifiers intended to be used for high quality power sources up to the kW-region. Multi-cell switch-mode amplifiers usually are operated in interleaved PWM resulting in effective output voltage harmonics being much higher than the cell´s switching frequency. This major advantage, however, is only given for ideally balanced DC-link voltages; actual systems typically will show low-frequency output voltage noise. For compensating this drawback, hence a closed loop hybrid output voltage filter concept is proposed formed by a combination of a switch-mode power and a linear-mode correction amplifier. The linear amplifier only has to deliver a few percent of the output power, compensating the switch-mode stages output voltage ripple, whereas the switch-mode system delivers nearly the whole output power. An interesting advantage of this system is that the linear amplifier can be designed concerning a comparatively low supply voltage as well as for low output current compared to the total system.

http://dx.doi.org/10.1109/EDPE.2017.8123265