Noise reduction in a voltage converter

1. A method for voltage conversion providing a reduction in an output ripple energy at a switching frequency of a voltage converter, the method comprising:

receiving an input voltage and providing an output voltage having a frequency component at the switching frequency;

generating a control signal based on the output voltage and a reference voltage;

switching the input voltage based on the control signal; and

randomly or pseudo-randomly modulating at least one of the reference voltage or a delay used to generate the control signal to provide a decrease in the output ripple energy at the switching frequency of the voltage converter.

2. The method of claim 1 comprising driving a load with the output voltage and wherein the switching frequency depends on the load.

3. The method of claim 2 comprising modulating an amplitude of the reference voltage with a time-varying random value or pseudo-random value to provide a reduction in the output ripple energy at the switching frequency of the voltage converter.

4. The method of claim 3 comprising converting at least a portion of output ripple energy at the switching frequency to energy at a different frequency.

5. The method of claim 3 wherein modulating the amplitude of the reference voltage includes providing a time-varying randomly generated trimming code to a digital-to-analog converter.

6. The method of claim 2 comprising delaying the control signal by a varying random amount of time to provide a reduction in the output ripple energy at the switching frequency of the voltage converter.

7. The method of claim 6 comprising converting at least a portion of output ripple energy at the switching frequency to energy at a different frequency.

8. The method of claim 6 comprising charging a capacitor with a time-varying randomly generated current based on the control signal to provide the delay in the control signal.

9. The method of claim 2 wherein modulating at least one of the reference voltage or a delay used to generate the control signal reduces an output ripple energy at a multiple of the switching frequency of the voltage converter.

10. The method of claim 1 , wherein the randomly or pseudo-randomly modulating of the at least one reference voltage or the delay used to generate the control signal is random.

11. The method of claim 1 , wherein the randomly or pseudo-randomly modulating of the at least one reference voltage or the delay used to generate the control signal is pseudo-random.

12. A voltage converter for providing a reduction in an output ripple energy at a switching frequency of the voltage converter, the voltage converter comprising:

switching voltage converter circuitry configured to receive an input voltage and provide an output voltage having a frequency component at the switching frequency;

a control element configured to provide a control signal based on the output voltage and a reference voltage, the control signal controlling the switching voltage converter circuitry; and

modulation circuitry configured to randomly or pseudo-randomly modulate at least one of the reference voltage or a delay used to generate the control signal to provide a decrease in the output ripple energy at the switching frequency of the voltage converter.

13. The voltage converter of claim 12 wherein the switching voltage converter circuitry is configured to drive a load with the output voltage and wherein the switching frequency depends on the load.

14. The voltage converter of claim 13 wherein the modulation circuitry is configured to modulate an amplitude of the reference voltage with a time-varying random value or pseudo-random value to provide a reduction in the output ripple energy at the switching frequency of the voltage converter.

15. The voltage converter of claim 14 wherein the modulation circuitry is configured to convert at least a portion of output ripple energy at the switching frequency to energy at a different frequency.

16. The voltage converter of claim 13 wherein the modulation circuitry is configured to provide a time-varying randomly generated or pseudo-randomly generated trimming code to a digital-to-analog converter.

17. The voltage converter of claim 16 comprising variable delay circuitry configured to delay the control signal by a varying random or pseudo-random amount of time to provide a reduction in the output ripple energy at the switching frequency of the voltage converter.

18. The voltage converter of claim 17 wherein the modulation circuitry is configured to convert at least a portion of output ripple energy at the switching frequency to energy at a different frequency.

19. The voltage converter of claim 17 comprising a current source configured to charge a capacitor with a time-varying current in response to the control signal to provide the delay in the control signal.

20. The voltage converter of claim 13 wherein modulating at least one of the reference voltage or a delay used to generate the control signal reduces an output ripple energy at a multiple of the switching frequency of the voltage converter.

21. The voltage converter of claim 12 wherein the control element includes a hysteretic comparator configured to provide a first control signal if the output voltage exceeds the reference voltage by a first threshold amount and a second control signal if the output voltage is less than the reference voltage by more than a second threshold amount.

22. The voltage converter of claim 12 , wherein the modulation circuitry is configured to randomly modulate the at least one of the reference voltage or the delay used to generate the control signal.

23. The voltage converter of claim 12 , wherein the modulation circuitry is configured to pseudo-randomly modulate the at least one of the reference voltage or the delay used to generate the control signal.

24. A voltage converter for providing a reduction in an output ripple energy at a switching frequency of the voltage converter, the voltage converter comprising:

means for receiving an input voltage and providing an output voltage having a frequency component at the switching frequency;

means for generating a control signal based on the output voltage and a reference voltage;

means for switching the input voltage based on the control signal; and

means for randomly or pseudo-randomly modulating at least one of the reference voltage or a delay used to generate the control signal to provide a decrease in the output ripple energy at the switching frequency of the voltage converter.