High dynamic class-D power amplifier

Class-D amplifiers have high efficiency and are used when high audio frequency power is necessary and also when low power consumption in battery powered equipment is required. A new kind of 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. Furthermore, the compensation mechanism leads to no additional current or voltage stress in the main switching stage. In the presented example the switching frequency of the main power processor is selected at only twice the required output bandwidth of the amplifier. 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 consumer as well as aerospace applications as due to the improved efficiency, and the battery lifetime can be increased without any quality reduction