Study Of Class D Audio Amplifier DAC Interpolation Filter

With the rapid development of information technology,and that of the extraordinary advancement of VLSI technology,and the amazing rising volume of shipment of the portable electronics products such as mobile phone,MP3 player and portable game pad,audio and video have entered the digital era.As one of the basic ways in digital signal processing area,people have been laying much greater emphasis on the precision of D/A and A/D converters,which are used in the data conversion and signal processing.Compared with other types of D/A converter,this kind of D/A converter based on the modulation of Sigma-Delta can reach very high resolution without any analog device of high precision and large scale.So they have gained wide application and a lot of focus.Interpolation is an important component of oversampled digital-to-analog conversion.By learning typical experiences and methods,the thesis introduces sampling and quantization of audio signals,the derivation of delta-sigma principle used in Class D amplifier,and an algorithm for conversion of a 2's complement to CSD(Canonic Signed Digit) number system.With the principle of digitial interpolation filter in oversampling DAC,the interpolation filter with 128 times oversampling rate based on the analysis of basic architecture of halfband filters and CIC(Cascade Integrator Comb) filters is designed.The design is described by Verilog HDL,which is simulated,synthesized and verified under QuartusⅡ.The results show that the design is reliably and perfectly and meet the design requirements.Multi-stage multi-rate signal processing is used to implement interpolation filter. The interpolation filter is implemented as a caseade of two halfband filters and four CIC filters.Halfband filter,using its symmetry of the impulse response,improves the rate of power consumption,and other properties.CSD is based on the ternary number (-1,0,1),which has the advantage of reducing the non-zero bits of the number.With the filter coefficients CSD coded,the hardware scale and cost is reduced.Multi-stage CIC filter in place of single-level structure which is an effective way to enhance the harmonic suppression may reduce consumed resource to a bare minimum.