Systems and methods for detection of load impedance of a transducer device coupled to an audio device

Patent metadata

Field	Value
Publication number	US-9479869-B2
Application number	US-201615042757-A
Country	US
Kind code	B2
Filing date	Feb 12, 2016
Priority date	Sep 16, 2013
Publication date	Oct 25, 2016
Grant date	Oct 25, 2016

Abstract

In accordance with systems and methods of the present disclosure, an audio device may include an electrical terminal, an audio circuit, and a transducer load detection circuit. The electrical terminal may couple a transducer device to the audio device. The audio circuit may generate an analog audio signal, wherein the analog audio signal is coupled to the electrical terminal. The transducer load detection circuit may detect a load impedance of the transducer device when the transducer device is coupled to the audio device from characteristics measured at the electrical terminal.

First claim

What is claimed is:

1. A method comprising:
generating, by an audio circuit configured to generate analog audio signals for playback to a listener of a transducer device coupled to an electrical terminal for coupling the transducer device to the audio circuit, a test analog audio signal substantially inaudible to the listener of the transducer device wherein the audio circuit further comprises a power amplifier having an audio input for receiving an audio input signal, an audio output for providing the analog audio signal, and a variable compensation capacitor;
coupling a test impedance to the electrical terminal, such that when the transducer device is coupled to the electrical terminal, the load impedance is coupled to the test impedance;
measuring a voltage or a current associated with the test impedance in response to the test analog audio signal; and
determining a value of the load impedance based on the voltage or the current; and
setting a capacitance of the variable compensation capacitor based on the load impedance.

2. The method of claim 1 , further comprising:
sequentially coupling the test impedance and one or more additional test impedances to the electrical terminal;
generating a corresponding test analog audio signal for each of the test impedance and additional test impedance;
measuring a voltage or a current associated with each of the test impedance and each additional test impedance in response to each corresponding test analog audio signal; and
determining the value of the load impedance based on at least one of the voltages or at least one of the currents.

3. The method of claim 1 , wherein the test analog audio signal comprises frequency content outside of the range of human hearing.

4. The method of claim 3 , wherein the test analog audio signal comprises only frequency content greater than approximately 20 kilohertz or frequency content lesser than approximately 50 hertz.

5. The method of claim 1 , further comprising:
providing from a charge pump power supply a power supply voltage to a power supply input of a power amplifier having an audio input configured to receive an audio input signal, and an audio output configured to generate the analog audio signal, wherein the charge pump power supply has a select input for selecting an operating mode of the power supply, such that in a first operating mode, the power supply voltage is equal to a first voltage, and such that in a second operating mode the power supply voltage is equal to a fraction of the first voltage; and
selecting the operating mode of the charge pump power supply based on the load impedance.

6. The method of claim 1 , wherein:
the audio circuit further comprises a power amplifier having an audio input for receiving an audio input signal, and an audio output for providing the analog audio signal; and
the method further comprises configuring a quiescent power profile of the power amplifier based on the load impedance.

7. The method of claim 1 , wherein the transducer device is a head set and the load impedance is indicative of a type of head set coupled to the electrical terminal.

8. An apparatus comprising:
an audio circuit comprising a power amplifier having an audio input for receiving an audio input signal, an audio output for providing the analog audio signal, and a variable compensation capacitor, the audio circuit configured to:
couple to an electrical terminal for coupling a transducer device having a load impedance to the audio circuit;
generate an analog audio signal for playback to a listener of the transducer device; and
generate a test analog audio signal substantially inaudible to the listener of the transducer device; and

a transducer load detection circuit configured to:
couple a test impedance to the electrical terminal, such that when the transducer device is coupled to the electrical terminal, the load impedance is coupled to the test impedance;
measure a voltage or a current associated with the test impedance in response to the test analog audio signal;
determine a value of the load impedance based on the voltage or the current; and
set a capacitance of the variable compensation capacitor based on the load impedance.

9. The apparatus of claim 8 , wherein:
the transducer load detection circuit is further configured to sequentially couple the test impedance and one or more additional test impedances to the electrical terminal;
the audio circuit is further configured to generate a corresponding test analog audio signal for each of the test impedance and additional test impedance; and
the transducer load detection circuit is further configured to:
measure a voltage or a current associated with each of the test impedance and each additional test impedance in response to each corresponding test analog audio signal; and
determine the value of the load impedance based on at least one of the voltages or at least one of the currents.

10. The apparatus of claim 8 , wherein the test analog audio signal comprises frequency content outside of the range of human hearing.

11. The apparatus of claim 10 , wherein the test analog audio signal comprises only frequency content greater than approximately 20 kilohertz or frequency content lesser than approximately 50 hertz.

12. The apparatus of claim 8 , wherein the audio circuit further comprises:
a power amplifier having an audio input configured to receive an audio input signal, an audio output configured to generate the analog audio signal, and a power supply input;
a charge pump power supply configured to provide a power supply voltage to the power supply input, wherein the charge pump power supply has a select input for selecting an operating mode of the power supply, such that in a first operating mode, the power supply voltage is equal to a first voltage, and such that in a second operating mode the power supply voltage is equal to a fraction of the first voltage; and
a control circuit configured to select the operating mode of the charge pump power supply based on the value of the load impedance.

13. The apparatus of claim 8 , wherein the audio circuit further comprises a power amplifier having an audio input for receiving an audio input signal, and an audio output for providing the analog audio signal, and wherein a quiescent power profile of the power amplifier is based on the load impedance.

14. The apparatus of claim 8 , wherein the transducer device is a head set and the load impedance is indicative of a type of head set coupled to the electrical terminal.

15. The apparatus of claim 8 , further comprising the electrical terminal, and wherein the apparatus is a personal audio device.

Assignees

• Cirrus Logic Inc

Inventors

• Ilango Anand
• Allen Daniel John
• Satoskar Aniruddha

Classifications

• H03F3/183

  with semiconductor devices only · CPC title

• G10K2210/30232

  Transfer functions, e.g. impulse response · CPC title

• H04R29/001

  for loudspeakers (H04R29/007 takes precedence) · CPC title

• H03F3/185

  with field-effect devices (H03F3/187 takes precedence) · CPC title

• H03F1/0227

  using supply converters · CPC title