选取一种典型的音频功率放大电路, 采用直接功率注入法研究了音频功放电源的电磁干扰效应。分析了电路的电磁干扰耦合机理, 设计了基于直接功率注入法的电源电磁干扰测试平台, 测试得到0.1~1 GHz电磁干扰对音频放大电路直流电源的干扰效果数据, 得出临界失真、典型失真和完全失真三种状态下的功率阈值与干扰频率规律曲线。结果表明: 测试频段内, 三种失真状态下的失真功率阈值随频率的变化关系一致, 失真功率阈值相差约2 dBm。当注入干扰的频率较低时(100~300 MHz), 失真功率阈值较高, 且随频率增大近似以幂函数趋势下降；当注入干扰频率高于300 MHz时, 失真功率阈值随频率增大呈减幅振荡趋势。

The direct power injection method was used to study the effect of electromagnetic interference coupling on the power supply of typical audio power amplifier circuits. The electromagnetic interference coupling characteristics of typical audio power amplifier circuits were analyzed. The electromagnetic interference test platform based on the direct power injection method was designed to test the electromagnetic interference effect on the DC power signal of the circuit in the range of 0.1-1 GHz. The power thresholds for the critical distortion, typical distortion and full distortion of the circuit and their laws with the interference frequency were obtained. The results show that in the test frequency band, the distortion power threshold has the same relationship with the frequency under the three distortion states, and the difference of distortion power threshold is about 2 dBm. When the injection interference frequency is lower (100-300 MHz), the distortion power threshold is higher, and decreases with the increase of the frequency in the trend of power function approximately. When the injection interference frequency is higher than 300 MHz, the distortion power threshold tends to damped oscillation with the increase of the frequency. The use of electromagnetic interference can affect the normal operation of audio electronic devices, which provides a new thought for the study on ultra-wide spectrum electromagnetic interference effects of audio integrated circuits.