System and method of predictive current feedback for switched mode regulators

1. A predictive current feedback system for a switched mode regulator, comprising:

a sample and hold network for sampling a voltage across a power switch of the regulator and for providing a hold signal indicative thereof; and

a predictive current feedback network which adds an offset adjustment to said hold signal based on a duration of a pulse width of a pulse control signal developed by the regulator; and wherein said offset adjustment comprises a predetermined incremental offset adjustment for each of a predetermined incremental time period during said pulse width.

2. The predictive current feedback system of claim 1 , wherein said predictive current feedback network adjusts said hold signal to provide a more accurate determination of current through an output inductor of the regulator.

3. The predictive current feedback system of claim 1 , wherein the pulse control signal toggles on and off, wherein said predictive current feedback network adds a first offset amount to said hold signal after each of at least one first incremental time period after a first nominal time period while the pulse control signal is on, and wherein said predictive current feedback network subtracts a second offset amount from said hold signal after each of at least one second incremental time period after a second nominal time period while the pulse control signal is off.

4. The predictive current feedback system of claim 1 , wherein the pulse control signal toggles on and off, wherein said predictive current feedback network adds a time varying signal to said hold signal after a first nominal time period while the pulse control signal is on, and wherein said sample and hold network tracks the voltage across the power switch after a second nominal time period while the pulse control signal is off.

5. An electronic device, comprising:

a modulator which receives an output voltage sense signal and a current sense signal and which develops a pulse control signal indicative thereof for controlling a switching regulator for regulating an output voltage;

a sample and hold network for sampling voltage of a phase node of said switching regulator and for providing a hold signal indicative thereof;

a predictive current feedback network which provides an offset adjustment to adjust said hold signal based on a duration of a pulse width of said pulse control signal to develop said current sense signal; and

wherein said predictive current feedback network is configured to incrementally add an offset to said hold signal for each of an incremental time period after a nominal time period while said pulse control signal is high.

6. The electronic device of claim 5 , further comprising:

an output node developing said output voltage; and

a load coupled to said output node.

7. The electronic device of claim 6 , wherein said load comprises a processor coupled to a memory.

8. The electronic device of claim 5 , wherein:

said switching regulator comprises:

an upper switch coupled between an input voltage node and said phase node;

a lower switch coupled between said phase node and a reference node;

an output inductor coupled between said phase node and an output node developing said output voltage; and

wherein said upper switch is turned on while said pulse control signal is high and wherein said lower switch is turned on while said pulse control signal is low; and

wherein said sample and hold network samples voltage across said lower switch while said pulse control signal is low and develops said hold signal indicative thereof.

9. A method of providing predictive current feedback for a switched mode regulator, comprising:

sampling voltage across a power switch during a first state of a pulse control signal and providing a hold value indicative thereof; and

adding an offset to said hold value during a second state of the pulse control signal in response to a load transient, wherein said adding an offset comprises adding a first offset value after each of a first incremental time period after a first nominal time period during the second state of the pulse control signal.

10. The method of claim 9 , further comprising subtracting a second offset value from said hold value after each of a second incremental time period after a second nominal time period during the first state of the pulse control signal.

11. The method of claim 9 , wherein said providing a hold value and said adding an offset to said hold value comprises generating a droop control signal for controlling output voltage droop based on load.

12. A predictive current feedback system for a switched mode regulator, comprising:

a sample and hold network for sampling a voltage across a power switch of the regulator and for providing a hold signal indicative thereof; and

a predictive current feedback network that adds an offset amount to said hold signal after each of at least one incremental time period after a nominal time period during a pulse width of a pulse control signal developed by the regulator.

13. A predictive current feedback system for a switched mode regulator, comprising:

a sample and hold network for sampling a voltage across a power switch of the regulator and for providing a hold signal indicative thereof;

a predictive current feedback network that adds an offset adjustment to said hold signal based on a duration of a pulse width of a pulse control signal developed by the regulator;

a counter network that provides a count value indicative of an on time duration and an off time duration of the pulse control signal;

wherein said sample and hold network comprises a first decoder which determines when to hold a sampled value while the pulse control signal is off based on said count signal during said off time duration; and

wherein said predictive current feedback network comprises a second decoder which determines when said on time duration of the pulse control signal exceeds each of an incremental time period after a predetermined nominal time period based on said count value and provides a corresponding offset value indicative thereof.

14. The predictive current feedback system of claim 13 , wherein:

said sample and hold network comprises:

a first converter which converts voltage across the power switch to sample values;

a memory which receives said sample values and provides a hold value in response to a hold indication from said first decoder; and

a second converter which converts said hold value to a hold current; and

wherein said predictive current feedback network comprises a third converter which converts said offset value to an offset current which is added to said hold current during said on time duration of the pulse control signal.

15. A method of providing predictive current feedback for a switched mode regulator, comprising:

sampling voltage across a power switch during a first state of a pulse control signal and providing a hold value indicative thereof;

adding an offset to said hold value during a second state of the pulse control signal in response to a load transient, wherein said adding an offset comprises adding a time-varying offset value to the hold value for after a first nominal time period during the second state of the pulse control signal; and

tracking voltage of the phase node after a second nominal time period during the first state of the pulse control signal to adjust the hold value.