Timucin David Karaca

EMI-receiver simulation model with quasi-peak detector

Computer aided design and simulations are an integral part in the development process of integrated circuits. In order to evaluate the electromagnetic compatibility (EMC) of integrated circuits in simulation, simulation models of the EMC measurement setup and the EMC measurement device are needed. In this work, an electromagnetic interference (EMI) receiver simulation model is presented. The EMI-reciever simulation model is intended to analyze electromagnetic emission (EME) of integrated circuits from transient simulations. The model is explained in detail and emulates an CISPR-16 conform test receiver. It is implemented using an STFT algorithm, and evaluates simulation output in CISPR Band-B/C/D with peak, average and quasi-peak detector. A quasi-peak detector model for pulsed disturbances is described, that significantly reduces simulation time compared to traditional implementations. The presented EMI-receiver model is verified with different test setups.

Characterization of EMI-reducing spread-spectrum techniques for class-D audio amplifiers

Audio amplifiers for portable devices need to be power efficient, therefore Class-D amplifiers are used. These amplifiers employ a switching output stage, so that they generally produce a significant amount of EMI. Filtering these frequency components usually is not an option since the amplifiers have to be small and lightweight. A reduction of EMI can be achieved by using spread-spectrum techniques that distribute the emissions over a wider frequency range. Unfortunately spread-spectrum techniques can impact the audio performance. This work presents a test setup for a Class-D prototype to evaluate different spread-spectrum methods by measurement or even by listening to the audio output. Using this setup several spread-spectrum methods are compared in terms of EMI-reduction and audio performance.

Electromagnetic evaluation of Class-D switching schemes

Class-D audio amplifiers may significantly contribute to the electromagnetic emissions of electronic devices. This work deals with the electromagnetic emissions created by Class-D amplifier output stages. Output stage switching schemes of traditional and filterless Class-D amplifiers are analyzed concerning their ability to create electromagnetic disturbances. Three different switching schemes are compared, namely Class-AD, Class-BD, and Ternary switching. Finally, commercially available Class-D amplifier ICs are measured and compared using an electromagnetic compatibility measurement setup according to IEC61967-4-A1.

Spread spectrum techniques for Class-D audio amplifiers to reduce EMI

For battery powered portable devices it is required to have circuits that combine high efficiency with a small footprint. In the case of Class-D amplifiers the high efficiency can be achieved by applying pulse-width modulation (PWM) to generate the desired output signal. Classical PWM requires an output filter to suppress the idle current. In order to avoid this filter a different modulation scheme is used, which however introduces a larger amount of electromagnetic emissions. Therefore spread-spectrum techniques are applied to distribute the emissions over a wider frequency range. In this article methods are discussed that allow the use of spread-spectrum modulation without introducing audible artifacts due to the modulation.ZusammenfassungFür batterieversorgte mobile Geräte werden Komponenten benötigt, die einerseits eine kleine Baugröße andererseits auch einen geringen Stromverbrauch aufweisen. Im Fall von Klasse-D-Verstärkern wird die hohe Effizienz dadurch erreicht, dass man Pulsweitenmodulation (PWM) verwendet, um das gewünschte Ausgangssignal zu erhalten. Klassische PWM benötigt ein Filter am Ausgang, um Ruheströme in der Last zu vermeiden. Zur Vermeidung dieses Filters setzt man andere Modulationsverfahren ein, welche ein größeres Maß an elektromagnetischen Emissionen erzeugen. Aus diesem Grund verwendet man Spread-Spectrum-Modulation, damit diese Emissionen über einen größeren Frequenzbereich verteilt werden. In diesem Beitrag werden Spread-Spectrum-Methoden vorgestellt, die auch für Audio-Anwendungen geeignet sind.

A Class-D output bridge with dynamic dead-time, small delay and reduced EMI

Power efficient Class-D audio amplifiers are very popular in mobile applications, despite the potential electromagnetic interference (EMI) caused by their output stage. Going to higher power levels, more effort has to be put into the reduction of EMI without sacrificing audio performance and efficiency. This work presents a Class-D output stage with an adaptive driver concept. The proposed driver monitors each output transition and dynamically adjusts dead-time and driver strength to reduce EMI while maintaining high audio fidelity. The presented concept is implemented in a 180nm CMOS technology and verified by measurement.