Departmental Bulletin Paper セグメントパルスシェーピング技術を用いた デジタル直接駆動型スピーカの構成検討

晴海, 豪

In this paper, we propose a novel digital-direct driven speaker architecture using segmented pulse shaping technique to reduce implementation area. The digital direct-driven speaker consists of amulti-bit delta-sigma modulator and a noise-shaping dynamic element matching circuit. Because the multi-bit outputs drive each of the driver circuits directly, the system can be driven at low voltage with high efficiency. However, it is necessary for the number of loudspeakers or voice coils and drivercircuits to be same as the number of quantization levels. Therefore, increasing the number of quantization levels is not a straightforward process. The segmented pulse shaping technique has been proposed to overcome the problem of digital-direct driven speaker. The technique can increase the number of quantization levels without increasing the number of output units, thereby improving the signal-to-noise ratio and reducing out-of-band noise. However, there is a disadvantage that the internal signal processing circuit area is increased. The method proposed here can reduce theimplementation area of the system using the segmented pulse shaping technique.Key Words : digital direct-driven speaker, delta-sigma modulator,segmented pulse shaping technique, NSDEM

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