The design of an analogue class-D audio amplifier usingZ-domainmethods

[摘要] ENGLISH ABSTRACT:The class-D audio power amplifier has found widespread use in both the consumer andprofessional audio industry for one reason: efficiency. A higher efficiency leads to a smallerand cheaper design, and in the case of mobile devices, a longer battery life.Unfortunately, the basic class-D amplifier has some serious drawbacks. These includehigh distortion levels, a load dependent frequency response and the potential to radiateEMI. Except for EMI, the aforementioned issues can be mitigated by the properimplementation of global negative feedback. Negative feedback also has the potential toindirectly reduce EMI, since the timing requirements of the output devices can be relaxed.This thesis discusses the design of a clocked analogue controlled pulse-width modulatedclass-D audio amplifier with global negative feedback. The analogue control loopis converted to the z-domain by modelling the PWM comparator as a sampling operation.A method is implemented that improves clip recovery and ensures stability duringover-modulation. Loop gain is shaped to provide a high gain across the audio band, andripple compensation is implemented to minimize the negative effect of ripple feedback.Experimental results are presented.

[发布机构] Stellenbosch University