Quiet Switching Controller for Audio Amplifiers

Analog amplifiers are still used in entertainment electronics, especially in the audio range. Switching controllers are now increasingly used as their power supplies, as they attain high efficiency. These are switched circuits that include various sources of interference and may lead to various types of electromagnetic interference. Classical interference, such as linebound interference, is not always the main problem in every circuit. In analog amplification circuits, switching controllers can cause non-linear distortions. Nonetheless, even analog circuits can be supplied with switching controllers, provided attention is paid to filtering of interference and the design of their circuit boards. However, filters are not all the same. Different filter coils are considered depending on the frequency associated with the interference. Wire coils with a relatively low self-resonant frequency are no longer considered for high frequency interference sources. SMD ferrites are selected for such cases. This Application Note addresses the EMC-compliant design of DC/DC switching controllers for analog audio amplifiers.