Advanced phase number control for multiphase converters

1. A multiphase voltage regulator, comprising:

switching circuitry for generating an output voltage responsive to the input voltage;

an error amplifier for generating an error correction voltage responsive to the output voltage and a reference voltage;

PWM logic for generating a phase signal for each phase of the multiphase buck converter responsive to the error correction voltage and at least one ramp voltage;

drive logic for generating control signals to the switching circuitry responsive to the phase signals; and

control circuitry for generating at least one control signal to add a phase as an output of the PWM logic responsive to a determination that the error correction voltage has exceeded a threshold level.

2. The multiphase voltage regulator of claim 1 , wherein the control circuitry further comprises:

a sampling circuit for sampling the error correction voltage;

a voltage source for providing a voltage offset to the error correction voltage to establish a threshold voltage; and

a comparator for comparing the sampled error correction voltage with the threshold voltage, wherein the comparator generates the at least one control signal to add the phase to the output of the PWM logic when the sampled error correction voltage exceeds the threshold voltage.

3. The multiphase voltage regulator of claim 2 , wherein the sampling circuit comprises a switch.

4. The multiphase voltage regulator of claim 1 , wherein the control circuitry further comprises:

a sampling circuit for sampling the error correction voltage;

a plurality of voltage sources for providing a plurality of voltage offsets to the sampled error correction voltage to establish a plurality of threshold voltages;

a plurality of comparators each associated with one phase of the multiphase voltage regulator having a first mode of operation wherein the comparator compares the error correction voltage with one of the plurality of threshold voltages when the phase associated with the comparator is not running and a second mode of operation wherein the comparator compares the error correction voltage with a ramp voltage associated with the phase when the phase associated with the comparator is running.

5. The multiphase buck converter of claim 4 , wherein the control circuitry further comprises a switch for switching between the ramp voltage and the one of the plurality of threshold voltages, the switch switching from the one of the plurality of threshold voltages to the ramp voltage responsive to a determination by the comparator that the error correction voltage exceeds the one of the plurality of threshold voltages.

6. A control circuit for generating a control signal to add phases to a multiphase voltage regulator, comprising:

an input for receiving an error correction voltage from an error amplifier of the multiphase voltage regulator;

at least one output for providing a PWM control signal;

control circuitry for generating at least one PWM control signal to add a phase to the multiphase voltage regulator responsive to a determination that the error correction voltage has exceeded a threshold level.

7. The control circuit of claim 6 , wherein the control circuitry further comprises:

a sampling circuit for sampling the error correction voltage;

a voltage source for providing a voltage offset to the error correction voltage to establish a threshold voltage; and

a comparator for comparing the sampled error correction voltage with the threshold voltage, wherein the comparator generates the at least one PWM control signal to add the phase to the multiphase voltage regulator when the sampled error correction voltage exceeds the threshold voltage.

8. The control circuit of claim 7 , wherein the sampling circuit comprises a switch.

9. The control circuit of claim 6 , wherein the control circuitry further comprises:

a sampling circuit for sampling the error correction voltage;

a plurality of voltage sources for providing a plurality of voltage offsets to the sampled error correction voltage to establish a plurality of threshold voltages;

a plurality of comparators each associated with one phase of the multiphase voltage regulator having a first mode of operation wherein the comparator compares the error correction voltage with one of the plurality of threshold voltages when the phase associated with the comparator is not running and a second mode of operation wherein the comparator compares the error correction voltage with a ramp voltage associated with the phase when the phase associated with the comparator is running.

10. The control circuit of claim 9 , wherein the control circuitry further comprises a switch for switching between the ramp voltage and the one of the plurality of threshold voltages, the switch switching from the one of the plurality of threshold voltages to the ramp voltage responsive to a determination by the comparator that the error correction voltage exceeds the one of the plurality of threshold voltages.

11. A method for adding phases to a multiphase voltage regulator, comprising the steps of:

receiving an error correction voltage from an error amplifier of the multiphase voltage regulator;

determining whether the error correction voltage has exceeded a threshold voltage level;

generating at least one PWM control signal to add a phase to the multiphase voltage regulator responsive to a determination that the error correction voltage has exceeded the threshold level; and

providing the at least one PWM control signal to control operation of the multiphase voltage regulator.

12. The method of claim 11 , wherein the step of determining further comprises the steps of:

sampling the error correction voltage;

adding a voltage offset to the error correction voltage to establish a threshold voltage; and

comparing the sampled error correction voltage with the threshold voltage.

13. The method of claim 12 , wherein the step of generating further comprises the step of generating the at least one PWM control signal to add the phase to the multiphase voltage regulator when the sampled error correction voltage exceeds the threshold voltage.

14. The method of claim 12 , wherein the step of sampling further comprises the step of switching a value of the error correction voltage to store a fixed value.

15. The method of claim 11 , wherein the step of determining further comprises the steps of:

sampling the error correction voltage;

adding a plurality of voltage offsets to the sampled error correction voltage to establish a plurality of threshold voltages;

comparing the sampled error correction voltage with one of the plurality of threshold voltages for each comparator of a plurality of comparators in a first mode of operation when the phase associated with the comparator is not running; and

comparing the sampled error correction voltage with a ramp voltage for each comparator of the plurality of comparators in a second mode of operation when the phase associated with the comparator is running.

16. The method of claim 15 wherein the step of generating further comprises the step of generating the at least one PWM signal responsive to the comparisons to add the phase to the multiphase voltage regulator when the sampled error correction voltage exceeds the at least one threshold voltage.

17. The method of claim 15 , further comprising the steps of:

determining whether the error correction voltage exceeds the one of the plurality of threshold voltages; and

switching between the ramp voltage and the one of the plurality of threshold voltages responsive to the determination of whether the error correction voltage exceeds the one of the plurality of threshold voltages.