Active output driver supply compensation for noise reduction
An electronic system, in some embodiments, comprises: a power source; a load coupled to the power source; an analog-to-digital converter, coupled to the power source and the load, that samples a fluctuating voltage supplied by the power source and generates a digital representation of said fluctuating voltage; control logic, coupled to the analog-to-digital converter, that generates an amplitude correction signal based on said digital representation of the fluctuating voltage and on a target voltage; correction logic, coupled to the control logic, that uses the amplitude correction signal and an audio signal to generate a switch control signal; and an output driver, coupled to the correction logic, that controls coupling between the power source and the load based on the switch control signal.
1. An electronic system, comprising:
a power source;
a load coupled to the power source;
an analog-to-digital converter, coupled to the power source and the load, that samples a fluctuating voltage supplied by the power source and generates a digital representation of said fluctuating voltage;
control logic, coupled to the analog-to-digital converter, that generates an amplitude correction signal based on said digital representation of the fluctuating voltage and on a target voltage;
correction logic, coupled to the control logic, that uses the amplitude correction signal and an audio signal to generate a switch control signal; and
an output driver, coupled to the correction logic, that controls coupling between the power source and the load based on the switch control signal.
2. The system of claim 1 , wherein said output driver comprises a Class-D amplifier.
3. The system of claim 1 , further comprising a variable current load that causes said fluctuating voltage to fluctuate.
4. The system of claim 1 , wherein the correction logic comprises a sigma-delta modulator.
5. The system of claim 1 , wherein the output driver comprises an H-Bridge circuit.
6. The system of claim 1 , wherein the switch control signal is a digital 1-bit bit stream.
7. The system of claim 1 , further comprising a voltage regulator, coupled between the power source and the load, to provide the load with a regulated voltage that is less than voltages between which the fluctuating voltage fluctuates.
8. The system of claim 7 , wherein the voltage regulator is disabled when a variable current load in the system is disabled, and wherein the voltage regulator is enabled when said variable current load is enabled.
9. The system of claim 1 , wherein the control logic generates the amplitude correction signal based at least in part on an extrapolation of multiple digitized samples of the fluctuating voltage.
10. The system of claim 1 , wherein the control logic generates the amplitude correction signal at least in part by determining or approximating a ratio of said digital representation and a nominal voltage from the power source.
11. An electronic system, comprising:
a variable current load;
a power source, coupled to the variable current load, that provides a fluctuating voltage due at least in part to the variable current load;
a second load;
one or more switches to control coupling between the power source and the second load;
a sampling system, coupled to the second load, to sample a voltage provided to the second load; and
a comparator, coupled to the sampling system, that uses the sampled voltage and a reference voltage to generate a switch control signal that controls the one or more switches.
12. The system of claim 11 , wherein the one or more switches comprise n-type metal oxide semiconductor field effect transistor (n-MOSFET) switches.
13. The system of claim 11 , wherein the sampling system comprises a sample and hold switch and at least one capacitor.
14. The system of claim 11 , wherein the sampling system samples the voltage provided to the second load comprises positive and negative signal levels as referenced to 0 volts and wherein the sampling system only samples the positive signals.
15. The system of claim 11 , wherein the second load is an audio speaker.
16. The system of claim 11 , wherein the electronic system is a hearing aid device that is at least partially inserted into a human ear.
17. The system of claim 11 , wherein the power source is a portable source such as a battery.
18. The system according to claim 11 , further comprising a voltage regulator, coupled in between the power source and the output driver, to provide the second load with a regulated voltage that is less than voltages between which the fluctuating voltage fluctuates.
19. An audio noise reduction method, comprising:
taking a first measurement of a power source voltage at a first time;
taking a second measurement of said power source voltage at a second time;
calculating a rate of change based on said first and second voltage measurements;
predicting a future power source voltage based on said rate of change;
generating an amplitude correction signal based on the future power source voltage and a target load voltage;
generating a switch control signal using the amplitude correction signal and an audio signal; and
controlling one or more switches using the switch control signal to regulate the provision of power to a load.
20. The method of claim 19 , further comprising using one or more decoupling capacitors in tandem with said power source.
21. The method of claim 19 , further comprising using a voltage regulator to maintain said power provided to the load at a level that is less than the voltage range within which the power source voltage fluctuates.