Filterless, Digital Class-BD Audio Amplifiers with Constant Common Mode Output Voltage

Stanisław Kuta, Witold Machowski, Wojciech Kołodziejski and Łukasz Chlastawa
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Stanisław Kuta: Polytechnic Faculty, University of Applied Sciences in Tarnów, Mickiewicza 8, 33-100 Tarnów, Poland
Witold Machowski: Faculty of Computer Science, Electronics and Telecommunications, Institute of Electronics, AGH University of Science and Technology, Mickiewicza 30, 30-059 Kraków, Poland
Wojciech Kołodziejski: Polytechnic Faculty, University of Applied Sciences in Tarnów, Mickiewicza 8, 33-100 Tarnów, Poland
Łukasz Chlastawa: Polytechnic Faculty, University of Applied Sciences in Tarnów, Mickiewicza 8, 33-100 Tarnów, Poland

Energies, 2021, vol. 14, issue 21, 1-16

Abstract: This paper presents new and original architectures and implementations of two filterless, open-loop digital Class-BD audio amplifiers with constant common mode (CM) output voltage. The first, low-power amplifier consists of four ultrahigh-current EL7158 pin drivers, the OUT pins of which form the H bridge. The drivers are controlled from the extended LBDD PWM modulator and have appropriately set voltage levels on the VL and VH pins. The second proposed amplifier consists of two cooperating H-bridge power stages (HBS) implemented on complementary MOSFET pairs and powered by two different voltages. Both HBSs are driven by four EL7158 pin drivers having appropriately adjusted voltage levels on the VL and VH pins and controlled by an extended LBDD PWM modulator. The hybrid 9 bit DPWM modulator uses a linearized Class-BD double-sided modulation scheme with pre-compensation, enabling the most faithful emulation of natural NBDD PWM and, thus, providing attractive spectral characteristics at the DM output. Basic SPICE simulations and experimental results of the proposed digital Class-BD amplifiers were compared with the conventional digital Class-BD amplifiers. The elimination of CM signals significantly contributes to the reduction in electromagnetic interference (EMI), particularly those produced on the cables connecting the loudspeaker to the HBS terminal. Proposed Class-BD amplifiers with original and new topologies, due to their simple design and easy control (no galvanic isolation of control signals and no floating bias power supplies), which generate no CM voltage and feature excellent DM performance, similar to conventional Class-BD amplifiers, are very attractive solutions for filterless Class-BD amplifiers.

Keywords: digital Class-D audio amplifier; filterless Class-D amplifier; linearized pulse width modulation (LPWM); electromagnetic interference (EMI) (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
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