Method and apparatus for enhancing voltage regulator transient response

1. A voltage regulator comprising:

a regulation control circuit configured to regulate an output voltage based on reducing error between an output feedback signal and a reference signal;

a droop control circuit configured to introduce a droop-related error between the output feedback signal and the reference signal, said droop control circuit comprising a first amplifier configured to generate a droop signal and a first combining circuit configured to add or subtract the droop signal from a first one of the output feedback and reference signals; and

a response-enhancing amplifier circuit configured to improve a transient response of the voltage regulator by amplifying the error seen by the regulation control circuit, said response-enhancing amplifier circuit comprising a second amplifier configured to generate a first error signal for input to the regulation control circuit based on amplifying a difference between the first one of the output feedback and reference signals and a remaining one of the output feedback and reference signals.

2. The voltage regulator of claim 1 , wherein the response-enhancing amplifier circuit further comprises a second combining circuit to add a desired common mode signal to the first error signal, such that the regulation control circuit receives the first error signal at a desired common mode signal level.

3. A voltage regulator comprising:

a regulation control circuit configured to regulate an output voltage based on reducing error between an output feedback signal and a reference signal;

a droop control circuit configured to introduce a droop-related error between the output feedback signal and the reference signal;

a response-enhancing amplifier circuit configured to improve a transient response of the voltage regulator by amplifying the error seen by the regulation control circuit; and

wherein the regulation control circuit comprises a Pulse Width Modulation (PWM) regulator comprising an error amplifier and a PWM comparator, said error amplifier configured to generate a regulation error signal for the PWM comparator responsive to error between first and second error amplifier input signals as derived from the output feedback and reference signals, and wherein said response-enhancing amplifier circuit is configured to generate one of said first and second error amplifier input signals by amplifying differences between the output feedback signal and the reference signal, said differences including any droop offsets as introduced by the droop control circuit.

4. The voltage regulator of claim 1 , wherein the regulation control circuit comprises a hysteretic regulator comprising a hysteretic comparator configured to generate a switching control signal responsive to first and second comparator input signals, and wherein said response-enhancing amplifier circuit is configured to generate one of said first and second comparator input signals by amplifying differences between the output feedback signal and the reference signal, said differences including any droop offsets as introduced by the droop control circuit.

5. The voltage regulator of claim 1 , wherein the second amplifier of the response-enhancing amplifier circuit is configured with an amplifier gain determined according to one or more regulation stability criteria associated with regulating the output voltage.

6. The voltage regulator of claim 1 , wherein the second amplifier of the response-enhancing amplifier circuit is configured with an amplifier frequency response determined according to one or more regulation stability criteria associated with regulating the output voltage.

7. A method of regulating an output voltage comprising:

controlling the output voltage based on reducing error between an output feedback signal and a reference signal;

imparting a desired amount of voltage droop in the output voltage by introducing a droop-related error between the output feedback signal and the reference signal; and

amplifying the error between the output feedback and reference signals, including any droop-related error, for input to an error sensing circuit of a regulation control circuit controlling the output voltage, such that control of the output voltage is made responsive to an amplified error;

wherein amplifying the error between the output feedback and reference signals, including any droop-related error, for input to an error sensing circuit of a regulation control circuit controlling the output voltage comprises amplifying differences between the output feedback signal and the reference signal with a response enhancing amplifier circuit, said differences including any droop-related error introduced by a droop control circuit.

8. The method of claim 7 , wherein introducing the droop-related error between the output feedback signal and the reference signal comprises adjusting a droop offset between the output feedback and reference signals according to the desired amount of voltage droop.

9. The method of claim 7 , wherein introducing the droop-related error between the output feedback signal and the reference signal comprises generating a droop signal and combining the droop signal with a first one of the output feedback and reference signals.

10. The method of claim 9 , wherein amplifying the differences between the output feedback signal and the reference signal with a response enhancing amplifier circuit, said differences including any droop-related error introduced by a droop control circuit, comprises generating an error input signal for input to the error sensing circuit of the regulation control circuit based on amplifying a difference between the first one of the output feedback and reference signals, and a second, remaining one of the output feedback and reference signals.

11. The method of claim 10 , further comprising adding a desired common mode signal to the error input signal, such that the error sensing circuit of the regulation control circuit receives the first error signal at a desired common mode signal level.

12. The method of claim 7 , wherein the regulation control circuit comprises a Pulse Width Modulation (PWM) regulator including an error amplifier as the error sensing circuit, said error amplifier configured to generate a regulation error signal responsive to error between first and second error amplifier input signals as derived from the output feedback and reference signals, and wherein amplifying the differences between the output feedback signal and the reference signal with a response enhancing amplifier circuit, said differences including any droop-related error introduced by a droop control circuit comprises generating one of said first and second error amplifier input signals by amplifying differences between the output feedback signal and the reference signal, said differences including any droop-related error.

13. The method of claim 7 , wherein the regulation control circuit comprises a hysteretic regulator comprising a hysteretic comparator configured to generate a switching control signal responsive to first and second comparator input signals, and wherein amplifying the differences between the output feedback signal and the reference signal with a response enhancing amplifier circuit, said differences including any droop-related error introduced by a droop control circuit, comprises generating one of said first and second comparator input signals by amplifying the differences between the output feedback signal and the reference signal, said differences including any droop-related error.

14. The method of claim 7 , further comprising setting an amplifier gain of the response-enhancing amplifier circuit according to one or more regulation stability criteria associated with controlling the output voltage.

15. The method of claim 7 , further comprising setting an amplifier frequency response of the response-enhancing amplifier circuit according to one or more regulation stability criteria associated with controlling the output voltage.