Control system using nonlinear delta-sigma modulator with switching period error compensation
A control system provides a control signal to a nonlinear plant that generates a response signal responsive to the control signal. The control system includes a detector that detects a predetermined value of a plant quantity, valley switching logic, coupled to the detector, to change a state of a plant switch when the plant quantity is minimized, and a pulse-width modulator, coupled to the valley switching logic, to generate a control signal that controls the plant switch. The valley switching logic includes a nonlinear delta-sigma modulator that compensates for an error in a plant response signal by adjusting the duration of an on-time of a plant switch to cause an average value of the plant response signal to converge toward a target signal value.
1. A signal processing system, comprising:
a nonlinear delta-sigma modulator that compensates for an error in a plant response signal by adjusting a duration of an on-time interval of a plant switching period to cause an average value of the plant response signal to converge toward a target signal value, wherein the nonlinear delta-sigma modulator includes:
a loop filter having an input;
a quantizer coupled to the loop filter, the quantizer having an output; and
a feedback path coupled between the output of the quantizer and the input of the loop filter, wherein the feedback path determines an error for a switching period of the plant switch.
2. The signal processing system of claim 1 , wherein the nonlinear delta-signal modulator comprises a square root delta-sigma modulator.
3. A signal processing system, comprising:
a nonlinear delta-sigma modulator that compensates for an error in a plant response signal by adjusting a duration of an on-time interval of a plant switching period to cause an average value of the plant response signal to converge toward a target signal value;
wherein the plant response signal is output current; and
wherein the nonlinear delta-sigma modulator adjusts an on-time of a plant switch in the plant switching period to compensate for a difference in the average value of the output current from the target signal value in a prior plant switching period.
4. A signal processing system, and further comprising:
a nonlinear delta-sigma modulator that compensates for an error in a plant response signal by adjusting a duration of an on-time interval of a plant switching period to cause an average value of the plant response signal to converge toward a target signal value; and
a switch state controller including the nonlinear delta-sigma modulator and further including a quantizer having an associated quantizer error, and wherein the nonlinear delta-sigma modulator further compensates for the quantizer error.
5. A signal processing system, comprising:
a nonlinear delta-sigma modulator that compensates for an error in a plant response signal by adjusting a duration of an on-time interval of a plant switching period to cause an average value of the plant response signal to converge toward a target signal value; and
a switching power converter that transfers energy from a time-varying voltage source through an inductor in response to a state of a power factor regulation switch controlled based on an output of the nonlinear delta-sigma modulator.
6. The signal processing system of claim 5 , and further comprising a pulse-width modulator, coupled to the nonlinear delta-sigma modulator, to generate a control signal that determines the state of the power factor regulation switch.
7. A signal processing system, comprising:
a nonlinear delta-sigma modulator that compensates for an error in a plant response signal by adjusting a duration of an on-time interval of a plant switching period to cause an average value of the plant response signal to converge toward a target signal value; and
a power factor correction circuit including the nonlinear delta-sigma modulator.
8. The signal processing system of claim 7 , and further comprising valley switching logic that synchronizes the plant switching period with occurrence of a minimum value of a detected plant signal.
9. A signal processing system, comprising:
a nonlinear delta-sigma modulator that compensates for an error in a plant response signal by adjusting a duration of an on-time interval of a plant switching period to cause an average value of the plant response signal to converge toward a target signal value, wherein the nonlinear delta-sigma modulator includes:
a loop filter having an input;
a quantizer coupled to the loop filter, the quantizer having an output; and
a feedback path coupled between the output of the quantizer and the input of the loop filter, wherein the feedback path determines an error for a plant switching period, wherein the feedback path further includes a combiner that calculates an accumulated error for multiple plant switching periods.
10. A signal processing system, comprising:
a nonlinear delta-sigma modulator that compensates for an error in a plant response signal by adjusting a duration of an on-time interval of a plant switching period to cause an average value of the plant response signal to converge toward a target signal value, wherein the nonlinear delta-sigma modulator includes:
a loop filter having an input;
a quantizer coupled to the loop filter, the quantizer having an output; and
a feedback path coupled between the output of the quantizer and the input of the loop filter, wherein the feedback path determines an error for a plant switching period;
wherein:
the nonlinear delta-sigma modulator includes a combiner coupled to the input of the loop filter that combines a modulator input with a signal from the feedback path; and
the feedback path determines the error based in part on the modulator input.
11. A control system to provide a control signal to a nonlinear plant that generates a response signal responsive to the control signal, the control system comprising:
valley switching logic to change a state of a plant switch when the plant quantity is minimized;
compensation logic including a nonlinear delta-sigma modulator that compensates for an error in a plant response signal by adjusting a duration of an on-time of a plant switch to cause an average value of the plant response signal to converge toward a target signal value; and
a pulse-width modulator, coupled to the valley switching logic and the compensation logic, to generate a control signal that controls the plant switch.
12. The control system of claim 11 , wherein:
the plant response signal is output current; and
the compensation logic adjusts the duration of assertion of the control signal by the pulse-width modulator in a plant switching period to compensate for a difference in the average value of the output current from the target signal value in a prior plant switching period.
13. The control system of claim 11 , wherein the nonlinear delta-signal modulator comprises a square root delta-sigma modulator.
14. The control system of claim 11 , wherein the compensation logic includes a quantizer having an associated quantizer error, and wherein the nonlinear delta-sigma modulator further compensates for the quantizer error.
15. The control system of claim 11 , wherein:
the plant includes a switching power converter that transfers energy from a time-varying voltage source through an inductor in response to a state of the plant switch; and
the compensation logic comprises a power factor correction circuit.
16. The control system of claim 11 , wherein the nonlinear delta-sigma modulator includes:
a loop filter having an input;
a quantizer coupled to the loop filter, the quantizer having an output; and
a feedback path coupled between the output of the quantizer and the input of the loop filter, wherein the feedback path determines an error for a switching period of the plant switch.
17. The control system of claim 16 , wherein the feedback path further includes a combiner that calculates an accumulated error for multiple plant switching periods.
18. The control system of claim 16 , wherein:
the nonlinear delta-sigma modulator includes a combiner coupled to the input of the loop filter that combines a modulator input with a signal from the feedback path; and
the feedback determines the error based in part on the modulator input.
19. A method of processing signals utilizing a nonlinear delta-sigma modulator, the method comprising:
in a nonlinear delta-sigma modulator, receiving a signal related via a nonlinear function to a time interval in a first plant switching period;
in a forward path of the nonlinear delta-sigma modulator, determining the time interval in the first plant switching period by application of a nonlinear loop filter; and
in a feedback path of the nonlinear delta-sigma modulator, compensating for an error in a plant response signal by adjusting a duration of the time interval in a subsequent second plant switching period to cause an average value of the plant response signal to converge toward a target signal value.
20. The method of claim 19 , wherein the plant response signal is output current.
21. The method of claim 19 , wherein the time interval is an on-time of a plant switch.
22. The method of claim 19 , wherein determining the time interval comprises applying square root loop filter.
23. The method of claim 19 , wherein:
the method further comprises, in the forward path of the nonlinear delta-sigma modulator, quantizing the time interval in a quantizer having an associated quantizer error;
wherein the compensating includes compensating for the quantizer error.
24. The method of claim 19 , and further comprising:
generating a pulse-width modulated control signal that determines the plant switching period based on an output of the forward path of the nonlinear delta-sigma modulator.
25. The method of claim 19 , and further comprising generating an input of the forward path in a power factor correction circuit that includes the nonlinear delta-sigma modulator.
26. The method of claim 19 , and further comprising:
in the feedback path, calculating an accumulated error for multiple plant switching periods.
27. The method of claim 19 , wherein:
in the forward path, summing a modulator input with a signal from the feedback path; and
the compensating includes determining the error based in part on the modulator input.