Voice coil temperature control based on an estimated voice coil temperature and a threshold
A system includes a gain control circuit configured to dynamically select a gain value based on an estimated temperature for a speaker voice coil, a base gain value, and a threshold temperature value. The system also includes a power control circuit configured to determine a power limit value based on the gain value. The system also includes a filter circuit configured to adjust values of a digitized audio signal based on the power limit value. The system also includes a digital-to-analog converter (DAC) coupled to the filter circuit and configured to convert a digital output of the filter circuit to an analog audio signal.
1. A system that comprises:
a gain control circuit configured to dynamically select a gain value based on an estimated temperature for a speaker voice coil, a base gain value, and a threshold temperature value;
a power control circuit configured to determine a power limit value based on the gain value;
a filter circuit configured to adjust values of a digitized audio signal based on the power limit value; and
a digital-to-analog converter (DAC) coupled to the filter circuit and configured to convert a digital output of the filter circuit to an analog audio signal.
2. The system of claim 1 , further comprising an amplifier configured to receive the analog audio signal and to provide an amplified version of the analog audio signal to a speaker associated with the speaker voice coil.
3. The system of claim 2 , wherein the filter circuit, the power control circuit, the gain control circuit, the DAC, and the amplifier are components of an integrated circuit.
4. The system of claim 2 , further comprising voltage and current sensors configured to provide voltage and current measurements of the speaker, wherein outputs from the voltage and current sensors are used to determine the estimated temperature for the speaker voice coil.
5. The system of claim 1 , wherein the gain control circuit selects the base gain value as the gain value when the estimated temperature is less than the threshold temperature value, and wherein the gain control circuit selects a reduced gain value, relative to the base gain value, as the gain value when the estimated temperature is equal to or greater than the threshold temperature value.
6. The system of claim 5 , wherein a reduced gain value is a function of the base gain value and a variable gain reduction factor that is a function of the threshold temperature value, a maximum supported ambient temperature value, a calibration temperature, the estimated temperature of the speaker voice coil, and a temperature rating for the speaker voice coil.
7. The system of claim 6 , wherein a reduced gain value is given as:
G_BASE
*
(
1
-
(
T_AM
-
T_CAL
T_CR
-
T_CAL
)
(
T_EST
-
T_DGT
T_CR
-
T_DGT
)
)
,
where G_BASE is the base gain value, T_DGT is the threshold temperature value, T_AM is the maximum supported ambient temperature value, T_EST is the estimated temperature of the speaker voice coil, T_CR is the temperature rating for the speaker voice coil, and T_CAL is a calibration temperature.
8. The system of claim 2 , wherein the filter circuit, the power control circuit, and the gain control circuit correspond to a digital signal processor in communication with a memory that stores filter instructions, power control instructions, and gain control instructions.
9. An amplifier device that comprises:
circuitry configured to dynamically select a gain value based on an estimated temperature for a speaker voice coil, a base gain value, and a threshold temperature value, to determine a power limit value based on the gain value, and to filter a digitized audio signal based on the power limit value;
a digital-to-analog converter (DAC) coupled to the circuitry and configured to convert a digital output of the circuitry to an analog audio signal; and
an amplifier configured to receive the analog audio signal and to provide an amplified version of the analog audio signal to a speaker associated with the speaker voice coil.
10. The amplifier device of claim 9 , wherein the circuitry, the DAC, and the amplifier are components of an integrated circuit.
11. The amplifier device of claim 9 , further comprising voltage and current sensors configured to provide voltage and current measurements of the speaker, wherein the circuitry is configured to determine the estimated temperature based on voltage and current measurements from the voltage and current sensors.
12. The amplifier device of claim 11 , further comprising analog-to-digital converters (ADCs) configured to convert voltage and current measurements from the voltage and current sensors to provide digitized voltage and current measurements of the speaker to the circuitry.
13. The amplifier device of claim 9 , wherein the circuitry selects the base gain value as the gain value when the estimated temperature is less than the threshold temperature value, and wherein the circuitry selects a reduced gain value, relative to the base gain value, as the gain value when the estimated temperature is equal to or greater than the threshold temperature value.
14. The amplifier device of claim 13 , wherein the reduced gain value is given as:
G_BASE
*
(
1
-
(
T_AM
-
T_CAL
T_CR
-
T_CAL
)
(
T_EST
-
T_DGT
T_CR
-
T_DGT
)
)
,
where G_BASE is the base gain value, T_DGT is the threshold temperature value, T_AM is a maximum supported ambient temperature value, T_EST is the estimated temperature of the speaker voice coil, T_CR is a temperature rating for the speaker voice coil, and T_CAL is a calibration temperature.
15. An audio signal amplification method that comprises:
receiving a digitized audio signal;
selecting a gain value for a digital filter based on an estimated temperature for a speaker voice coil, a base gain value, and a threshold temperature value;
determining a power limit value based on the gain value;
filtering the digitized audio signal based on the power limit value;
converting a result of said filtering into an analog audio signal; and
amplifying the analog audio signal.
16. The method of claim 15 , further comprising:
obtaining voltage and current measurements of a speaker associated with the speaker voice coil; and
determining the estimated temperature for the speaker voice coil based on voltage and current measurements.
17. The method of claim 16 , further comprising:
converting the voltage and current measurements to digitized voltage and current measurements, wherein said determining the estimated temperature is based on the digitized voltage and current measurements.
18. The method of claim 15 , wherein selecting the gain value comprises:
selecting the base gain value as the gain value when the estimated temperature is less than the threshold temperature value; and
selecting a reduced gain value, relative to the base gain value, as the gain value when the estimated temperature is equal to or greater than the threshold temperature value.
19. The method of claim 15 , wherein a reduced gain value is given as:
G_BASE
*
(
1
-
(
T_AM
-
T_CAL
T_CR
-
T_CAL
)
(
T_EST
-
T_DGT
T_CR
-
T_DGT
)
)
,
where G_BASE is the base gain value, T_DGT is the threshold temperature value, T_AM is a maximum supported ambient temperature value, T_EST is the estimated temperature of the speaker voice coil, T_CR is a temperature rating for the speaker voice coil, and T_CAL is a calibration temperature.
20. The method of claim 19 , wherein determining the power limit value comprises adjusting the gain value based on an error value.