Dynamic switching frequency control in multiphase voltage regulators

1. A multiphase voltage regulator, comprising:

a plurality of phases, each phase configured to output a phase current to a load through an inductor in response to a control signal input to the phase; and

a controller operable to:

generate the control signals input to the phases;

set a switching frequency of the control signals to a first value; and

change the switching frequency from the first value to a second value different than the first value if the load current changes repetitively at a frequency that is within a predetermined range of the first value of the switching frequency.

2. The multiphase voltage regulator of claim 1 , wherein the controller is operable to adjust a duty cycle of one or more of the control signals to balance the phase currents, and change the switching frequency from the first value to the second value if the phase currents cannot be balanced without exceeding a peak current limit of the inductors.

3. The multiphase voltage regulator of claim 1 , wherein the controller is operable to change the switching frequency from the first value to the second value if the difference between two of the phase currents exceeds a threshold value for longer than a defined time interval.

4. The multiphase voltage regulator of claim 3 , wherein the threshold value and the defined time interval are selected so that the controller is operable to change the switching frequency from the first value to the second value before a peak current limit of the inductors is exceeded.

5. The multiphase voltage regulator of claim 1 , wherein the controller is operable to determine the second value from a lookup table or based on a formula programmed into the controller.

6. The multiphase voltage regulator of claim 1 , wherein the controller is operable to measure the frequency at which the load current changes, and change the switching frequency from the first value to the second value if the difference between the measured frequency of the load current and the first value is within a bandwidth of the controller.

7. The multiphase voltage regulator of claim 6 , wherein the controller is operable to measure the rate of change of an output voltage of the multiphase voltage regulator and convert the measured rate of change to a frequency indicative of the frequency at which the load current changes.

8. The multiphase voltage regulator of claim 1 , wherein the controller is operable to determine a phase current imbalance frequency based on phase current measurements taken for the plurality of phases, and change the switching frequency from the first value to the second value if the measured phase current imbalance frequency is lower than a threshold frequency.

9. The multiphase voltage regulator of claim 1 , wherein the controller is operable to change the switching frequency from the second value back to the first value if the frequency at which the load current changes repetitively moves to within a predetermined range of the second value of the switching frequency.

10. The multiphase voltage regulator of claim 1 , wherein the controller is operable to change the switching frequency from the second value back to the first value after detecting no dynamic load transients over a defined time interval.

11. A method of operating a multiphase voltage regulator that has a plurality of phases, each phase configured to output a phase current to a load through an inductor in response to a control signal input to the phase, the method comprising:

setting a switching frequency of the control signals to a first value; and

changing the switching frequency from the first value to a second value different than the first value if the load current changes repetitively at a frequency that is within a predetermined range of the first value of the switching frequency.

12. The method of claim 11 , wherein changing the switching frequency from the first value to the second value comprises:

adjusting a duty cycle of one or more of the control signals to balance the phase currents; and

changing the switching frequency from the first value to the second value if the phase currents cannot be balanced without exceeding a peak current limit of the inductors.

13. The method of claim 11 , wherein changing the switching frequency from the first value to the second value comprises:

measuring the phase currents; and

changing the switching frequency from the first value to the second value if the difference between two of the phase currents exceeds a threshold value for longer than a defined time interval.

14. The method of claim 13 , further comprising:

selecting the threshold value and the defined time interval so that the switching frequency changes from the first value to the second value before a peak current limit of the inductors is exceeded.

15. The method of claim 11 , further comprising:

determining the second value from a lookup table or based on a formula programmed into a controller of the multiphase voltage regulator.

16. The method of claim 11 , wherein changing the switching frequency from the first value to the second value comprises:

measuring the frequency at which the load current changes; and

changing the switching frequency from the first value to the second value if the difference between the measured frequency of the load current and the first value is within a bandwidth of a controller of the multiphase voltage regulator.

17. The method of claim 16 , wherein measuring the frequency at which the load current changes comprises:

measuring the rate of change of an output voltage of the multiphase voltage regulator; and

converting the measured rate of change to frequency.

18. The method of claim 11 , wherein changing the switching frequency from the first value to the second value comprises:

determining a phase current imbalance frequency based on phase current measurements taken for the plurality of phases; and

changing the switching frequency from the first value to the second value if the measured phase current imbalance frequency is lower than a threshold frequency.

19. The method of claim 11 , further comprising:

changing the switching frequency from the second value back to the first value if the frequency at which the load current changes repetitively moves to within a predetermined range of the second value of the switching frequency.

20. The method of claim 11 , further comprising:

changing the switching frequency from the second value back to the first value after detecting no dynamic load transients over a defined time interval.