Better Than Class D: Predictive Energy Balancing Can Boost Efficiency And Fidelity Of Cell Phone Audio Amplifiers

by Tom Lawson, CogniPower, Malvern, Penn, How2Power Today, Mar 15 2013

Focus:
Building a good class D audio amplifier revolves around removing unwanted harmonics, distortion, and noise from the audio output. According to this article those ends can be achieved more effectively using Predictive Energy Balancing (PEB), a method of control originally developed for SMPSs. Because PEB allows an output to be regulated precisely on a cycle-by-cycle basis, instead of on the average, PEB enables a new form of switched-mode amplifier. This article describes the operation of a PEB audio amplifier, comparing its efficiency and fidelity against class D audio amps with Spice results showing the PEB amplifier achieves better efficiency, less distortion, better PSRR, higher output-voltage capability, elimination of subharmonic noise, and other benefits. One intriguing possibility is using the PEB amp’s bidirectionality for energy harvesting in cell phones. A PEB amp demo board is introduced, its capabilities are briefly described, and some demo board measurements are shown to confirm the accuracy of simulated results. This discussion focuses mainly on amplifiers used in cell phones and other handheld devices, but this article also describes how the PEB amplifier design may benefit high-power and high-fidelity audio amplifiers.

What you’ll learn:

• How to improve the efficiency and audio fidelity of audio amplifiers using designs based on Predictive Energy Balancing in place of class D switching

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