A Class-D Piezoelectric Speaker Driver Using A Quadrature Feedback Chopping Scheme achieving 29dB Large-Signal THD+N Improvement
Shoubhik Karmakar (TU Delft - Electrical Engineering, Mathematics and Computer Science)
Huajun Zhang (TU Delft - Electrical Engineering, Mathematics and Computer Science, TU Delft - Electrical Engineering, Mathematics and Computer Science)
Marco Berkhout (Goodix Technologies)
Qinwen Fan (TU Delft - Electrical Engineering, Mathematics and Computer Science)
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Abstract
This paper presents a Class-D piezoelectric speaker driver that employs a quadrature feedback chopping scheme (QCS). Compared to a conventional single feedback chopping scheme (SCS), the use of QCS can eliminate the timing skew between low-voltage (LV) and high-voltage (HV) choppers, greatly improving large-signal linearity. A prototype implemented in a 180nm BCD process achieves a peak THD+N of 88dB/-92.5dB for a 1kHz/6kHz input frequency and 37μ VR MS output noise (A-weighted) while driving a 4μ F load. Thanks to QCS, the large-signal THD+N has been improved by 29 dB, while the output voltage swing achieving -60dB THD+N has been extended from 86.9% to 99.5% of the full-scale (FS).