A 20W/channel Class-D Amplifier with Significantly Reduced Common-Mode Radiated Emissions

📋 论文概要

该论文提出了一种20W/通道的Class-D音频放大器，通过改进调制技术显著降低了共模辐射发射，解决了传统Class-D放大器因轨到轨开关特性产生的电磁干扰问题。

💡 主要创新点

• 提出了一种降低共模辐射的调制方案，减少了共模输出信号的轨到轨摆幅。
• 在保持高效率的同时，使放大器满足FCC Class-B等EMI标准。

🏷 关键词

📄 原文摘要

Due to their rail-to-rail switching nature, Class-D audio amplifiers are prone to generating electromagnetic interference (EMI) that is in excess of what is acceptable in many systems. Such systems typically require devices to limit their EMI to an accepted standard, such as the FCC Class-B standard. In ClassD audio amplifiers that employ Class-BD modulation [1] using a single supply, the common-mode output signal, VCM, has a significant EMI component because this signal also swings rail-to-rail at the amplifier switching frequency, typically in the hundreds of kHz. This phenomenon is illustrated in the upper signals of Fig. 26.4.1. The higher harmonics of VCM are present at unacceptable levels in the frequency range of interest for radiated emissions, from 30MHz to 1GHz. This is because the amplitude of the fundamental of VCM can be up to 24Vpp in many Class-D amplifier applications, such as flat screen televisions. To counter this

👥 作者与机构

Patrick P. Siniscalchi, Richard K. Hester

Texas Instruments, Dallas, TX