Compensated class-D amplifier as high quality AC-voltage source

Class-D amplifiers have high efficiency and are used when high output power with high efficiency is required. An improved class-D amplifier is presented and analyzed. The ripple of the high power class-D amplifier stage is compensated by a small (low power) high dynamic amplifier, which can be realized either as an analog one or as a second power class-D converter. The main part of the power is handled by a half-bridge with relatively small switching frequency (compared to the output bandwidth) and therefore low switching losses. The resulting output ripple is compensated by using the transformer-coupled supplement power processor. Only small filters are necessary. The concept is well suited for high quality AC-sources and mains simulators.