Digital-to-analog converter for reducing pop noise and harmonic tone and related converting method

Patent metadata

Field	Value
Publication number	US-9391633-B2
Application number	US-49034509-A
Country	US
Kind code	B2
Filing date	Jun 24, 2009
Priority date	Jun 26, 2008
Publication date	Jul 12, 2016
Grant date	Jul 12, 2016

Abstract

A digital-to-analog converting (DAC) circuit is utilized for converting a 1-bit stream into an analog output signal. The DAC includes an N-bit encoder, a multiplexer, a low-pass filter, and a digital-to-analog conversion circuit. The N-bit encoder is utilized for receiving the 1-bit stream and encoding the 1-bit stream to generate an N-bit stream, where N is larger than 1; the multiplexer is utilized for selectively outputting the N-bit stream or a zero signal as an output signal according to a selection signal; the low-pass filter is utilized to generate a filtered output signal according to the output signal; and the digital to analog conversion circuit is utilized to generate the analog output signal according to the filtered output signal.

First claim

What is claimed is:

1. An apparatus for converting a digital audio signal into an analog audio signal, the apparatus comprising:
a first circuit configured to receiving the digital audio signal and converting the digital audio signal into an N-bit sigma-delta modulation signal, wherein N is larger than 1;
a multiplexer, for receiving the N-bit sigma-delta modulation signal and a zero signal, and selectively outputting the N-bit sigma-delta modulation signal or the zero signal as an output signal according to a selection signal;
a low-pass filter, coupled to the multiplexer, for generating a filtered output signal according to the output signal, wherein the filtered output signal is a pulse-code modulation (PCM) signal; and
a digital-to-analog converter, coupled to the low-pass filter, for generating the analog audio signal according to the filtered output signal.

2. The apparatus of claim 1 , wherein the digital audio signal is 1-bit sigma-delta modulation signal.

3. The apparatus of claim 1 , wherein the first circuit comprises a storage unit and a N-bit encoder.

4. The apparatus of claim 1 , wherein the selection signal corresponds to an amount of the digital audio signal in the first circuit.

5. The apparatus of claim 1 , further comprising: a volume control unit for adjusting the filtered output signal.

6. A digital-to-analog converting (DAC) circuit for converting a 1-bit stream, comprising:
an N-bit encoder for receiving the 1-bit stream encoding the 1-bit stream to generate an N-bit stream, wherein N is larger than 1;
a multiplexer, for receiving the N-bit stream and a zero signal, and selectively outputting the N-bit stream or the zero signal as an output signal according to a selection signal;
a low-pass filter, coupled to the multiplexer, for generating a filtered output signal according to the output signal, wherein the filtered output signal generated from the low-pass filter is a pulse-code modulation (PCM) signal; and
a digital-to-analog conversion circuit, coupled to the low-pass filter, for generating an analog output signal according to the filtered output signal.

7. The DAC circuit of claim 6 , wherein N is equal to 2.

8. The DAC circuit of claim 6 , further comprising: a storage unit for temporarily storing 1-bit stream.

9. The DAC circuit of claim 8 , wherein when the storage device is not empty, the multiplexer outputs the N-bit stream according to the selection signal; and when the storage device is empty, the multiplexer outputs the exactly zero signal according to the selection signal.

10. The DAC circuit of claim 6 , wherein the 1-bit stream is a sigma-delta modulated signal.

11. The DAC circuit of claim 6 , wherein the 1-bit stream is over-sampled at a sampling rate of M*44.1 kHz.

12. The DAC circuit of claim 6 , further comprising a volume control unit and a modulator.

13. The DAC circuit of claim 12 , wherein the modulated output signal generated from the modulator is a 4-bit stream.

14. A method for processing a digital audio signal to generate an analog audio signal, the method comprising:
processing the digital audio signal to generate an N-bit stream; receiving a zero signal;
selectively outputting the N-bit stream or the zero signal as an output signal according to a selection signal;
filtering the output signal to generate a filtered output signal, wherein the filtered output signal is a pulse-code modulation (PCM) signal; and
converting the filtered output signal into the analog audio signal.

15. The method of claim 14 , wherein N is equal to 2.

16. The method of claim 14 , further comprises: storing the digital audio signal into a storage unit, wherein the selection signal corresponds to a data amount stored in the storage unit.

17. The method of claim 14 , wherein the digital audio signal is a 1-bit sigma-delta modulated signal.

18. The method of claim 14 , wherein the filtered output signal is adjusted and modulated before the filtered output signal is converted.

Assignees

• Lin Wei-Chun
• Tu Yi-Chang
• Realtek Semiconductor Corp

Inventors

• Lin Wei-Chun
• Tu Yi-Chang

Classifications

• H03M3/30

  Delta-sigma modulation · CPC title

• H03M3/376

  Prevention or reduction of switching transients, e.g. glitches · CPC title

• H03M1/1215

  using time-division multiplexing · CPC title

• H03M3/358

  of non-linear distortion, e.g. instability (avoiding instability by structural design H03M3/44) · CPC title

• H03M3/346 Primary

  by suppressing active signals at predetermined times, e.g. muting, using non-overlapping clock phases · CPC title