Effects of AC Line Noises on the Output Signalof an Audio Ampilfier

• Main Authors: Jung-Hsien Hu, 胡榮顯
• Other Authors: Sung-Pei Yang
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/33678826511251465349

碩士 === 崑山科技大學 === 電機工程研究所 === 103 === In this thesis, the study about the effects of AC line noises on the output signal of an audio amplifier is presented. The commercially available audio filters are also applied to the power source to ensure that the ac line noises can be degraded through those filters. Therefore, the clear signal can be obtained from the output of the audio amplifier. This thesis also introduces the knowledge about the electromagnetic interference (EMI) and the standard US FCC Part 15 Class B Conducted. In addition, the common noise sources of household appliances are listed as follows. a. Motors. b. Switching mode power supply. c. In rush curren. d. VHF, UHF and Wi-Fi (2.4G band) radio waves. e. Electronic ballasts. They will be applied to the ac power source of the audio amplifier to derive the effects on the output signal. Accordingly, a test circuit system, including ac power source, a full-bridge rectifier, filters, a audio amplifier and a horn, is built. The output signals of the audio amplifier under different cases are thus measured by the digital oscilloscope. Based on the experimental results, we can know that the effects of the ac line noises on the output signal of the audio amplifier are not obvious.