Input current limited power supply and audio power amplifier for high power reproduction of nondeterministic signals

Patent metadata

Field	Value
Publication number	US-9209767-B1
Application number	US-201414288566-A
Country	US
Kind code	B1
Filing date	May 28, 2014
Priority date	May 28, 2014
Publication date	Dec 8, 2015
Grant date	Dec 8, 2015

Abstract

A method and apparatus for amplifying audio signals without exceeding an input current limit budgeted for the audio power amplifier circuit includes an intermediate energy storage between a battery and the audio power amplifier which provides an energy reserve to support amplifying peaks where the peaks have a peak power that is greater than the power that can be drawn from the battery due to the input current limit. Speech signals, which include substantial periodic content having short peaks relative to a pitch period, can be amplified without depleting the intermediate energy storage, allowing the intermediate energy storage to recover after a peak and before occurrence of a next peak. When an audio signal is amplified that results in depletion of the intermediate energy storage, a depletion recovery circuit reduces the overall audio gain to reduce the power demand of the audio power amplifier so as to substantially avoid distortion.

First claim

I claim:

1. A method for powering an audio power amplifier, comprising:
boosting a voltage level of a battery to a boost voltage level across a boost capacitor at an output of a boost stage without exceeding a preselected input current limit, the boost voltage level being higher than the voltage level of the battery and higher than a supply voltage required for the audio power amplifier to output a predefined maximum peak power into a load;
deriving the supply voltage from the boost voltage and providing the supply voltage to the audio power amplifier to power the audio power amplifier;
the audio power amplifier amplifying an input signal to produce an amplified signal;
comparing a state of charge indication parameter to a depletion threshold, wherein the state of charge indication parameter is dependent on the boost voltage; and
when the state of charge indication parameter is below the depletion threshold, adjusting a gain of a pre-amplifier that provides the input signal to the audio power amplifier.

2. The method of claim 1 , wherein adjusting the gain comprises reducing the gain of the pre-amplifier.

3. The method of claim 2 , wherein reducing the gain of the pre-amplifier is performed by reducing the gain at a preselected rate of decibels over time.

4. The method of claim 1 , further comprising when the gain of the pre-amplifier is below a maximum gain and the state of charge indication parameter is at or above a depletion threshold, increasing the gain of the pre-amplifier.

5. The method of claim 4 , wherein increasing the gain of the pre-amplifier is performed by increasing the gain at a preselected rate of decibels over time.

6. The method of claim 1 , wherein deriving the supply voltage comprises stepping the boost voltage down in a buck stage between the boost stage and the audio power amplifier, an output of the buck stage providing the supply voltage.

7. The method of claim 6 , wherein the state of charge indication parameter is the supply voltage provided to the audio power amplifier.

8. The method of claim 1 , wherein the supply voltage is the output of the boost stage to the audio power amplifier.

9. The method of claim 1 , wherein the current limit is based on an input current budget limit for a power amplifier circuit that performs the method.

10. The audio power amplifier circuit of claim 9 , wherein the supply voltage is produced by a buck stage that steps the boost voltage down to the supply voltage.

11. The audio power amplifier circuit of claim 10 , wherein the state of charge indication parameter is the supply voltage.

12. The audio power amplifier circuit of claim 9 , wherein the supply voltage is the boost voltage level, and wherein the audio power amplifier steps the boost voltage level down to form an amplified audio signal.

13. The audio power amplifier circuit of claim 9 , wherein the input gain stage decreases the input gain when the state of charge indication parameter falls below the depletion threshold.

14. The audio power amplifier circuit of claim 13 , wherein the input gain stage decreases the input gain at a preselected rate of decibels over time while the state of charge indication parameter is below the depletion threshold.

15. The audio power amplifier circuit of claim 9 , wherein the input gain stage increases the input gain when the input gain is below a maximum gain value and the state of charge indication parameter is at or above a depletion threshold.

16. The audio power amplifier circuit of claim 15 , wherein the input gain stage increases the input gain at a preselected rate of decibels over time while the state of charge indication parameter is at or above a depletion threshold and the input gain is below the maximum gain value.

17. An audio power amplifier circuit, comprising:
a boost stage that produces a boost voltage level from a battery voltage without exceeding a preselected current limit for a current budget of the audio power amplifier, wherein the boost voltage level is provided across a boost storage capacitor;
an audio power amplifier that is supplied at a supply voltage level derived from the boost stage and amplifies an input signal; and
an input gain stage that provides the input signal and which adjusts an input gain of the input signal based on a level of a state of charge indication parameter relative to a depletion threshold, where the state of charge indication parameter is dependent on the boost voltage.

18. A portable two-way radio device, comprising:
a transceiver that receives an audio signal in a radio frequency (RF) signal and extracts the audio signal from the RF signal;
an audio power amplifier circuit that includes a boost stage that produces a boost voltage level from a battery voltage without exceeding a preselected input current budget limit of the audio power amplifier circuit, wherein the boost voltage level is provided across a boost storage capacitor;
the audio power amplifier circuit further including an audio power amplifier that amplifies an input signal and is supplied at a supply voltage level derived from the boost stage;
the audio power amplifier circuit further including a pre-amplifier that amplifies the audio signal at an adjustable gain setting to provide the input signal to the audio power amplifier; and
the audio power amplifier circuit further including a depletion recovery control circuit that adjusts the adjustable gain setting of the pre-amplifier based on a level of state of charge indication parameter level relative to a depletion threshold where the state of charge indication parameter is dependent on the boost voltage.

19. The portable two-way radio device of claim 18 , wherein the supply voltage is produced by a buck stage that steps the boost voltage down to the supply voltage level.

20. The portable two-way radio device of claim 19 , wherein the state of charge indication parameter is the supply voltage level.

21. The portable two-way radio device of claim 18 , wherein the supply voltage is the boost voltage level, and wherein the audio power amplifier steps the boost voltage level down to form an amplified audio signal.

22. The portable two-way radio device of claim 18 , wherein, in response to the state of charge indication parameter falling below the depletion threshold, the depletion recovery control circuit decreases the adjustable gain of the pre-amplifier at a preselected rate of decibels over time.

23. The portable two-way radio device of claim 18 , wherein, in response to the state of charge indication parameter rising above a depletion threshold while the adjustable gain of the pre-amplifier is below a maximum gain setting, the depletion recovery control circuit increases the adjustable gain of the pre-amplifier at a preselected rate of decibels over time.

Assignees

• Motorola Solutions Inc
• Motorola Solutions Inc

Inventors

• Svendsen Peter William Hilding

Classifications

• H03F3/181

  Low-frequency amplifiers, e.g. audio preamplifiers · CPC title

• H03F2200/03

  the amplifier being designed for audio applications · CPC title

• H04W52/0261 Primary

  managing power supply demand, e.g. depending on battery level · CPC title

• H03G3/004 Primary

  Control by varying the supply voltage · CPC title

• H03F1/52

  Circuit arrangements for protecting such amplifiers {(monitoring arrangements G01R31/28; increasing reliability in communication systems, e.g. using redundancy H04B1/74)} · CPC title