Sigma-delta modulated amplifier

• US 7,084,799 B1
• Filed: 06/13/2005
• Issued: 08/01/2006
• Est. Priority Date: 05/09/2005
• Status: Active Grant

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: SLS International Incorporated
• Inventors: Butler, Joel
• Primary Examiner(s): JEAN PIERRE, PEGUY
• Application Number:
  US11/151,331
• Time in Patent Office: 414 Days
• Field of Search: 341/143, 341/155, 341/144, 341/122, 341/123, 375/238
• US Class Current: 341/143
• CPC Class Codes: H03F 3/2175 using analogue-digital or digital-analogue conversion H03F3/2173 takes precedence
• CPC Class Codes: H03M 3/3283 the dither being in the time domain
• CPC Class Codes: H03M 3/43 the quantiser being a single bit one
• CPC Class Codes: H03M 3/456 the modulator having a first order loop filter in the feedforward path

Abstract

A sigma-delta modulated amplifier is disclosed that is operable to sum an input signal and a feedback signal, integrate the summed signal, asynchronously quantize the integrated signal, sample the quantized signal utilizing a pseudo-random osculating signal, and amplify the sampled signal. The amplifier enables discrete implementation of a low-cost, spread spectrum controlled, sigma delta modulated audio amplifier for spectrally pure, high efficiency, low EMI, audio power amplification.

Claims

1. A sigma-delta modulated audio amplifier including:

a local oscillator operable to provide a pseudo-random oscillating signal;

a summation and integration stage operable to receive an input signal and a feedback signal and to sum and integrate the received signals to provide an integrated signal;

a quantization stage coupled with the summation and integration stage to receive the integrated signal, the quantization stage operable to quantize the integrated signal to provide a quantized signal;

a frequency randomized sampling stage coupled with both the quantization stage and the local oscillator to receive the quantized signal and the pseudo-random oscillating signal, the sampling stage operable to provide a sampled signal by utilizing the quantized signal and the oscillating signal;

an output stage coupled with the sampling stage and operable to amplify the sampled signal to provide an output signal and the feedback signal; and

an output filter stage coupled with the output stage and operable to provide an audio frequency signal by filtering the output signal.

2. The amplifier of claim 1, wherein the quantization stage is operable to asynchronously quantize the integrated signal to enable continuous quantization.

3. The amplifier of claim 1, wherein the frequency randomized sampling stage provides the sampled signal and an inverted sampled signal to enable switch-mode amplification of the sampled signals by the output stage.

4. The amplifier of claim 3, further including a digital dead time stage coupled with the frequency randomized sampling stage and operable to time space the inverted sampled signal and the sampled signal by a fixed amount.

5. The amplifier of claim 1, further including a feedback stage coupled with the output stage and the summation and integration stage, the feedback stage being operable to filter the feedback signal.

6. The amplifier of claim 1, further including an isolating device coupled with at least one of the stages and operable to provide electrical isolation to the amplifier.

7. A sigma-delta modulated audio amplifier including:

a local oscillator operable to provide a pseudo-random oscillating signal;

a summation and integration stage operable to receive an input signal and a feedback signal and to sum and integrate the received signals to provide an integrated signal;

a quantization stage coupled with the summation and integration stage to receive the integrated signal, the quantization stage operable to continuously quantize the integrated signal to provide a quantized signal;

a frequency randomized sampling stage coupled with both the quantization stage and the local oscillator to receive the quantized signal and the oscillating signal, the sampling stage operable to provide a randomized sampled signal and an inverted randomized sampled signal by utilizing the quantized signal and the oscillating signal;

a digital dead time stage coupled with the frequency randomized sampling stage to receive the sampled signal and the inverted sampled signal, the dead time stage operable to provide a first fixed time spaced drive signal utilizing the sampled signal and a second fixed time spaced drive signal utilizing the inverted sampled signal;

an output stage coupled with the dead time stage to receive the drive signals, the output stage operable to provide a digital output signal through switch-mode amplification of the received drive signals;

a feedback stage coupled with both the summation and integration stage and the output stage to receive the output signal, the feedback stage operable to provide the feedback signal to the summation and integration stage by filtering the output signal; and

an output filter stage coupled with the output stage and operable to provide an audio frequency signal by filtering the output signal.

8. The amplifier of claim 7, wherein the summation and integration stage includes an operational amplifier arranged in a summation and integration configuration.

9. The amplifier of claim 7, wherein the quantized signal is a 1-bit signal and the quantization stage comprises an asynchronous logic gate.

10. The amplifier of claim 7, wherein the sampling stage comprises a D-flip flop having a data input and a clock input, the data input being coupled with the quantization stage to receive the quantized signal and the clock input being coupled with the local oscillator to receive the oscillating signal.

11. The amplifier of claim 7, wherein the dead time stage includes a plurality of AND logic gates and a plurality of resistive-capacitive delay circuits coupled with inputs of the AND logic gates.

12. The amplifier of claim 7, wherein the output stage includes a transistor driver coupled with two transistors positioned in a half-bridge configuration.

13. The amplifier of claim 7, wherein the feedback stage includes a divider, a low-pass filter, and a high-pass filter.

14. The amplifier of claim 7, wherein the output filter stage includes an inductor-capacitor filter.

15. The amplifier of claim 7, wherein the output filter stage is coupled with a speaker to provide audible sound.

16. The amplifier of claim 7, further including an isolating device operable to provide electrical isolation to the amplifier, the isolating device being coupled between the quantization stage and the frequency randomized sampling stage.

17. A method of amplifying an input signal, the method including:

summing the input signal and a feedback signal to provide a summed signal;

integrating the summed signal to provide an integrated signal;

quantizing the integrated signal to provide a quantized signal;

sampling the quantized signal utilizing a pseudo-random oscillating signal to provide a sampled signal;

amplifying the sampled signal to provide an output signal and the feedback signal; and

filtering the output signal to provide an audio frequency signal.

18. The method of claim 17, wherein the quantized signal is sampled to provide the sampled signal and an inverted sample signal and the output signal is provided through switch-mode amplification of the sampled signals.

19. The method of claim 18, further including time spacing the inverted sampled signal and the sampled signal.

20. The method of claim 17, wherein the integrated signal is continuously and asynchronously quantized.