Methods and apparatus to protect circuitry from overcurrent conditions
An example apparatus includes: programmable circuitry configured to execute machine-readable instructions to: receive first voltages representative of an input signal; receive second voltages and currents, the second voltages and currents representative of voltages and currents of filter circuitry responsive to the first voltages; and determine a transfer function based on the first voltages and the second voltages and currents, the transfer function having coefficients representing the filter circuitry.
1 . An apparatus comprising:
programmable circuitry configured to execute machine-readable instructions to:
receive a first input signal having first voltages;
receive second voltages and first currents, the second voltages and first currents representing voltages and currents of filter circuitry responsive to the first voltages;
determine a transfer function based on the first voltages, second voltages, and first currents, the transfer function having coefficients representing the filter circuitry; and
predict second currents based on third voltages and the coefficients of the transfer function, the third voltages representing a second input signal subsequent to the first input signal.
2 . The apparatus of claim 1 , wherein the programmable circuitry is further configured to:
compare the second currents to a current limit;
determine a gain based on the second currents and the current limit; and
modify the second input signal by the gain.
3 . The apparatus of claim 1 , wherein the programmable circuitry is further configured to:
receive fourth voltages and third currents of the filter circuitry, the fourth voltages and third currents representing voltages and currents of the filter circuitry responsive to the third voltages;
predict fourth currents based on the fourth voltages and the coefficients of the transfer function; and
determine a difference between the third currents and the fourth currents.
4 . The apparatus of claim 3 , wherein the programmable circuitry is further configured to adjust the coefficients of the transfer function based on the difference between the third currents and the fourth currents.
5 . The apparatus of claim 1 , wherein the programmable circuitry is further configured to modify the coefficients of the transfer function to modify the transfer function.
6 . The apparatus of claim 1 , further comprising:
an amplifier having an input and an output, the input of the amplifier coupled to the programmable circuitry;
the filter circuitry having a first terminal, a second terminal, and a third terminal, the first terminal of the filter circuitry coupled to the programmable circuitry, the second terminal of the filter circuitry coupled to the output of the amplifier; and
a speaker having a terminal coupled to the third terminal of the filter circuitry.
7 . A system comprising:
filter circuitry having an input and an output;
an amplifier having an input and an output, the output of the amplifier coupled to the input of the filter circuitry; and
protection circuitry having an input and an output, the input of the protection circuitry coupled to the output of the filter circuitry, the output of the protection circuitry coupled to the input of the amplifier, the protection circuitry configured to:
receive a sense voltage responsive to supplying an input signal, the sense voltage representing a voltage of the filter circuitry;
predict a sense current based on the sense voltage and coefficients of a transfer function that represents the filter circuitry;
receive the sense current responsive to supplying the input signal to the filter circuitry; and
adjust the coefficients based on differences between the predicted sense current and the sense current of the filter circuitry.
8 . The system of claim 7 , wherein the protection circuitry is further configured to:
supply a calibration signal as the input signal to the amplifier;
receive the sense current and the sense voltage responsive to supplying the calibration signal; and
determine the coefficients of the transfer function based on the sense current and the sense voltage.
9 . The system of claim 7 , wherein the protection circuitry is further configured to:
determine currents of the input signal based on the input signal and the coefficients;
determine a peak current of the currents of the input signal;
determine a gain based on the peak current and a current limit; and
modify the input signal by the gain.
10 . The system of claim 7 , wherein the input signal is a first input signal, the protection circuitry is further configured to convert voltages of a second input signal to currents of the second input signal based on the coefficients.
11 . The system of claim 7 , wherein the protection circuitry is further configured to limit a current supplied to the amplifier based on the input signal and the coefficients.
12 . The system of claim 7 , wherein the protection circuitry is further configured to reduce differences between the predicted sense current and the sense current of the filter circuitry.
13 . The system of claim 7 , wherein the output of the filter circuitry is a first output, the filter circuitry having a second output, the system further comprising a piezoelectric speaker coupled to the second output of the filter circuitry.
14 . At least one non-transitory computer readable storage medium comprising instructions that, when executed, cause programmable circuitry to at least:
receive a first input signal;
receive first voltages and first currents responsive to supplying the input first signal to an amplifier, the first voltages and first currents representing voltages and currents of filter circuitry;
determine coefficients based on the first input signal, first voltages, and first currents, the coefficients of a transfer function representing the filter circuitry; and
receive second voltages and second currents of the filter circuitry responsive to supplying a second input signal to the amplifier.
15 . The at least one non-transitory computer readable storage medium of claim 14 , wherein the instructions further cause the programmable circuitry to:
predict third currents based on the coefficients and the second voltages of the filter circuitry; and
determine a difference between the second currents of the filter circuitry and the third currents.
16 . The at least one non-transitory computer readable storage medium of claim 15 , wherein the instructions further cause the programmable circuitry to adjust the coefficients based on the difference between the second currents of the filter circuitry and the third currents.
17 . The at least one non-transitory computer readable storage medium of claim 14 , wherein the instructions further cause the programmable circuitry to:
receive a third input signal having third voltages, and
determine third currents of the filter circuitry based on the third voltages and the coefficients.
18 . The at least one non-transitory computer readable storage medium of claim 17 , wherein the instructions further cause the programmable circuitry to:
determine a gain based on differences between the third currents and a current limit; and
modify the third voltages by the gain.