Digitally assisted EMI-reduction techniques for Class-D amplifiers with digital control

Class-D amplifiers are known for their excellent efficiency but also for their high potential to produce electromagnetic interference (EMI). Typically Class-D amplifiers operate in the analog domain, but there is a clear trend to replace some of the functionality by digital circuitry, requiring new approaches to reduce their emissions. In this paper a prototype of a digitally controlled Class-D amplifier is used to present digital techniques to reduce EMI with various methods. A new method is realized and the advantages of digitally assisted EMI reduction methods are demonstrated. Measurement results show that a considerable (up to 17.8 dB) reduction of EMI is possible taking advantage of digitally assisted EMI reduction techniques while delivering state-of-the art audio performance.