Systems and methods for predictive switching in audio amplifiers

Patent metadata

Field	Value
Publication number	US-10128803-B2
Application number	US-201615136548-A
Country	US
Kind code	B2
Filing date	Apr 22, 2016
Priority date	Apr 22, 2016
Publication date	Nov 13, 2018
Grant date	Nov 13, 2018

Abstract

An audio amplifier circuit for providing an output signal to an audio transducer may include a power amplifier and a control circuit. The power amplifier may include an audio input for receiving an audio input signal, an audio output for generating the output signal based on the audio input signal, and a power supply input for receiving a power supply voltage, wherein the power supply voltage is variable among at least a first supply voltage and a second supply voltage greater than the first supply voltage. The control circuit may be configured to predict, based on one or more characteristics of a signal indicative of the output signal, an occurrence of a condition for changing the power supply voltage, and responsive to predicting the occurrence of the condition, change, at an approximate zero crossing of the signal indicative of the output signal, the power supply voltage.

First claim

What is claimed is:

1. An audio amplifier circuit for providing an output signal to an audio transducer, the audio amplifier circuit comprising:
a power amplifier having an audio input for receiving an audio input signal, an audio output for providing the output signal, and a power supply input for receiving a power supply voltage, wherein the power amplifier generates the output signal based on the audio input signal and wherein the power supply voltage is variable among at least a first supply voltage and a second supply voltage greater than the first supply voltage;
a control circuit configured to:
predict, based on one or more characteristics of a signal indicative of the output signal, an occurrence of a condition for changing the power supply voltage; and
responsive to predicting the occurrence of the condition, change, at an approximate zero crossing of the signal indicative of the output signal, the power supply voltage.

2. The audio amplifier circuit of claim 1 , wherein the condition for changing the power supply voltage comprises the magnitude of the signal indicative of the output signal crossing a predetermined threshold magnitude.

3. The audio amplifier circuit of claim 2 , wherein the control circuit is configured to predict the condition of the signal indicative of the output signal crossing the predetermined threshold magnitude responsive to the magnitude of the signal indicative of the output signal increasing above a second predetermined threshold magnitude less than the predetermined threshold magnitude.

4. The audio amplifier circuit of claim 2 , wherein the control circuit is configured to predict the condition of the signal indicative of the output signal crossing the predetermined threshold magnitude responsive to the magnitude of the signal indicative of the output signal decreasing below a second predetermined threshold magnitude greater than the predetermined threshold magnitude.

5. The audio amplifier circuit of claim 2 , wherein the control circuit is configured to predict the condition of the signal indicative of the output signal crossing the predetermined threshold magnitude by:
tracking signal peaks of the signal indicative of the output signal;
extrapolating from the signal peaks a future value of the magnitude of the signal indicative of the output signal; and
predicting that the magnitude of the signal indicative of the output signal will cross the predetermined threshold magnitude based on the future value.

6. The audio amplifier circuit of claim 2 , wherein the control circuit is configured to predict the condition of the signal indicative of the output signal crossing the predetermined threshold magnitude by:
tracking a signal envelope of the signal indicative of the output signal;
extrapolating from the envelope a future value of the magnitude of the signal indicative of the output signal; and
predicting that the magnitude of the signal indicative of the output signal will cross the predetermined threshold magnitude based on the future value.

7. The audio amplifier circuit of claim 2 , wherein the condition for changing the power supply voltage comprises the magnitude of the signal indicative of the output signal lacking a persistent pattern of magnitude relative to the predetermined threshold magnitude.

8. The audio amplifier circuit of claim 7 , wherein the control circuit is further configured to detect the persistent pattern.

9. The audio amplifier circuit of claim 1 , wherein the control circuit is further configured to:
predict, based on a magnitude of a signal indicative of the output signal, an occurrence of a second condition for changing the power supply voltage; and
responsive to predicting the occurrence of the second condition, change, at an approximate zero crossing of the signal indicative of the output signal, the power supply voltage to be equal to a third supply voltage.

10. The audio amplifier circuit of claim 9 , wherein:
the condition for changing the power supply voltage comprises the magnitude of the signal indicative of the output signal increasing from below a predetermined threshold magnitude to above the predetermined threshold magnitude; and
the second condition for changing the power supply voltage comprises the magnitude of the signal indicative of the output signal increasing from below a second predetermined threshold magnitude to above the second predetermined threshold magnitude, wherein the second predetermined threshold magnitude is greater than the predetermined threshold magnitude.

11. The audio amplifier circuit of claim 10 , wherein the control circuit is further configured to:
predict, based on a magnitude of a signal indicative of the output signal, an occurrence of a third condition for changing the power supply voltage, wherein the third condition for changing the power supply voltage comprises the magnitude of the signal indicative of the output signal decreasing from above the predetermined threshold magnitude to below the predetermined threshold magnitude; and
responsive to predicting the occurrence of the third condition, change, at an approximate zero crossing of the signal indicative of the output signal occurs, the power supply voltage to the first supply voltage.

12. The audio amplifier circuit of claim 11 , wherein the control circuit is further configured to:
predict, based on a magnitude of a signal indicative of the output signal, an occurrence of a fourth condition for changing the power supply voltage, wherein the fourth condition for changing the power supply voltage comprises the magnitude of the signal indicative of the output signal decreasing from above the second predetermined threshold magnitude to below the second predetermined threshold magnitude; and
responsive to predicting the occurrence of the fourth condition, change, at an approximate zero crossing of the signal indicative of the output signal occurs, the power supply voltage to the second supply voltage.

13. The audio amplifier circuit of claim 1 , wherein the condition for changing the power supply voltage comprises the magnitude of the signal indicative of the output signal refraining from crossing a predetermined threshold magnitude for a period of time.

14. The audio amplifier circuit of claim 13 , wherein the control circuit is further configured to:
initialize a timer of a predetermined duration responsive to the magnitude of the signal indicative of the output signal decreasing from above the predetermined threshold magnitude to below the predetermined threshold magnitude;
responsive to the magnitude of the signal indicative of the output signal increasing from below a second predetermined threshold magnitude lesser than the predetermined threshold magnitude to above the second predetermined threshold magnitude before expiration of the timer, reinitialize the timer for the predetermined duration; and
responsive to the expiration of the timer, change the power supply voltage at an approximate zero crossing of the signal indicative of the output signal occurs.

15. The audio amplifier circuit of claim 13 , wherein the control circuit is further configured to:
initialize a timer of a predetermined duration responsive to the magnitude of the signal indicative of the output signal decreasing from above the predetermined threshold magnitude to below the predetermined threshold magnitude; and
responsive to the expiration of the timer prior to the signal indicative of the output signal increasing from below the predetermined threshold magnitude to above the predetermined threshold magnitude, change the power supply voltage at an appr

Assignees

• Cirrus Logic Int Semiconductor Ltd
• Cirrus Logic Inc

Inventors

• Das Tejasvi
• Melanson John L
• King Eric J

Classifications

• H03F2200/321

  Use of a microprocessor in an amplifier circuit or its control circuit · CPC title

• H03F1/025 Primary

  by using a signal derived from the input signal · CPC title

• H03F3/2175 Primary

  using analogue-digital or digital-analogue conversion (H03F3/2173 takes precedence) · CPC title

• H03F1/0222 Primary

  by using a signal derived from the input signal · CPC title

• H03F3/187

  in integrated circuits · CPC title