Method and circuit for controlling an output of an audio signal of a battery-powered device

1. A method for controlling an output of an audio signal of a battery powered device, the method comprising: detecting whether the audio signal is output via a loudspeaker or an earphone; detecting a charge condition of a battery of the battery powered device; (-cancelled) adjusting a filtering of the audio signal in response to the detected charge condition and depending on whether the audio signal is output via the loudspeaker or the earphone.

2. The method of claim 1 , wherein the filtering is adjusted such that the lower the charge condition of the battery is the higher the attenuation of lower frequencies of the audio signal is.

3. The method of claim 2 , wherein the lower frequencies are in the range of 0 to 800 Hz.

4. The method of claim 1 , wherein at least three different charge condition ranges are defined for the battery, and at least three different filtering settings are defined, each of the at least three filtering settings being associated with a different one of the at least three charge condition ranges, the method further comprising:

detecting to which charge condition range of the at least three charge condition ranges the current charge condition of the battery corresponds, and

adjusting the filtering according to the one of the at least three filtering settings that corresponds to the detected charge condition range.

5. The method of claim 1 , further comprising:

adjusting a dynamic range compression for the audio signal in response to the detected charge condition of the battery.

6. A method for controlling an output of an audio signal of a battery powered device, the method comprising: detecting whether the audio signal is output via a loudspeaker or an earphone, detecting a charge condition of a battery of the battery powered device, and adjusting a dynamic range compression of the audio signal in response to the detected charge condition of the battery and depending on whether the audio signal is output via the loudspeaker or the earphone, wherein the dynamic range compression comprises a gain reduction for higher levels of the audio signal, and wherein the dynamic range compression is set such that the lower the charge condition of the battery is the lower the gain reduction for higher levels of the audio signal is.

7. The method of claim 6 , wherein at least three different charge condition ranges are defined for the battery, and at least three different dynamic range compression settings are defined, each of the at least three dynamic range compression settings being associated with a different one of the at least three charge condition ranges, the method further comprising:

detecting to which charge condition range of the at least three charge condition ranges the current charge condition of the battery corresponds, and

adjusting the dynamic range compression according to the one of the at least three dynamic range compression settings that corresponds to the detected charge condition range.

8. The method of claim 6 , further comprising:

detecting, whether the audio signal is output via a loudspeaker or an earphone, and

adjusting the dynamic range compression additionally in response to the detection, whether the audio signal is output via the loudspeaker or the earphone.

9. The method of claim 6 , further comprising:

adjusting a filtering of the audio signal in response to the detected charge condition of the battery.

10. A control circuit for controlling an output of an audio signal of a battery powered device, the control circuit comprising:

a battery input for detecting a charge condition of a battery of the battery powered device;

an input for detecting whether the audio signal is output via a loudspeaker or an earphone; and

a filter control output for controlling an audio filter for filtering the audio signal, wherein the control circuit is configured to control the audio filter in response to the detected charge condition of the battery and depending on whether the audio signal is output via the loudspeaker or the earphone.

11. The control circuit of claim 10 , wherein the control circuit is configured to adjust the audio filter such that the lower the charge condition of the battery is the higher the attenuation of lower frequencies of the audio signal is.

12. The control circuit of claim 11 , wherein the lower frequencies are in the range of 0 to 800 Hz.

13. The control circuit of claim 10 , wherein at least three different charge condition ranges are defined for the battery, and at least three different settings for the audio filter are defined, each of the at least three settings being associated with a different one of the at least three charge condition ranges, the control circuit being further configured:

to detect to which charge condition range of the at least three charge condition ranges the current charge condition of the battery corresponds, and to supply to the audio filter the setting of the at least three settings that corresponds to the detected charge condition range.

14. The control circuit of claim 10 , further comprising a compressor control output for controlling a compressor adjusting a dynamic range compression for the audio signal, the control circuit being further configured to control the compressor in response to the detected charge condition of the battery.

15. A control circuit for controlling an output of an audio signal of a battery powered device, the control circuit comprising: an input for detecting whether the audio signal is output via a loudspeaker or an earphone, a battery input for detecting a charge condition of a battery of the battery powered device, and a compressor control output for controlling a compressor for adjusting a dynamic range compression of the audio signal, wherein the control circuit is configured to control the compressor in response to the detected charge condition of the battery and depending on whether the audio signal is output via the loudspeaker or the earphone, and the dynamic range compression of the compressor comprises a gain reduction for higher levels of the audio signal, and wherein the control circuit is configured to control the compressor such that the lower the charge condition of the battery is the lower the gain reduction for higher levels of the audio signal is.

16. The control circuit of claim 15 , wherein at least three different charge condition ranges are defined for the battery, and at least three different settings for the compressor are defined, each of the at least three settings being associated with a different one of the at least three charge condition ranges, the control circuit being further configured to:

detect to which charge condition range of the at least three charge condition ranges the current charge condition of the battery corresponds, and

supply to the compressor the setting of the at least three settings that corresponds to the detected charge condition range.

17. The control circuit of claim 15 , further comprising an input for detecting, whether the audio signal is output via a loudspeaker or an earphone, wherein the control circuit is configured to control the compressor additionally in response to the detection, whether the audio signal is output via the loudspeaker or the earphone.

18. The control circuit of claim 15 , further comprising a filter control output for controlling an audio filter for filtering the audio signal, the control circuit being further configured to control the audio filter in response to the detected charge condition of the battery.

19. A mobile device, comprising: an audio signal source configured to provide an audio signal to be output by the mobile device, a battery configured to supply the mobile device with energy, an audio filter configured to filter the audio signal, a compressor configured to adjust a dynamic range compression for the audio signal, and a control circuit comprising: an input for detecting whether the audio signal is output via a loudspeaker or an earphone; a battery input coupled to the battery for detecting a charge condition of the battery, a filter control output coupled to the audio filter for controlling the audio filter, and a compressor control output coupled to the compressor for controlling the compressor, wherein the control circuit is configured to control the audio filter and the compressor in response to the detected charge condition of the battery and depending on whether the audio signal is output via the loudspeaker or the earphone, and the dynamic range compression of the compressor comprises a gain reduction for higher levels of the audio signal, and wherein the control circuit is configured to control the compressor such that the lower the charge condition of the battery is the lower the gain reduction for higher levels of the audio signal is.

20. The mobile device according to claim 19 , wherein the mobile device is a device selected from the group comprising a mobile phone, a personal digital assistant, a mobile audio playback device, and a mobile computer.