In recent years, digital class D power amplifiers have attracted widespread attention in the audio electronics field due to their high efficiency and seamless integration with digital audio sources. As one of the crucial digital signal processing modules in digital class D amplifiers, the Sigma-Delta modulator plays a pivotal role for digital audio signal processing. The noise-shaping characteristic of the Sigma-Delta modulator can reduce the implementation cost of the power amplifier system while maintaining or even improving the output signal-to-noise ratio of the system, and can suppress the noise introduced by some signal transmission paths. Firstly, the working principle and mainstream architecture of digital D-class power amplifiers were summarized. Then, based on the basic principle of Sigma-Delta modulators, the design schemes of Sigma-Delta modulators used in digital D-class power amplifiers in recent years were discussed, with a focus on the architecture design and noise transfer function design of Sigma-Delta modulators. Finally, the research and development of Sigma-Delta modulators for digital D-class power amplifiers were summarized.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |