Ripple correlation control based on limited sampling

• US 7,681,090 B2
• Filed: 01/25/2007
• Issued: 03/16/2010
• Est. Priority Date: 01/25/2007
• Status: Expired due to Fees

• Current Assignee: Enphase Energy Incorporated
• Original Assignee: Solarbridge Technologies Incorporated (Totalenergies Se)
• Inventors: Kimball, Jonathan W., Krein, Philip T.
• Primary Examiner(s): Chung; Phung M
• Application Number:
  US11/626,911
• Publication Number:
  US 20080183338A1
• Time in Patent Office: 1,146 Days
• Field of Search: 714/700, 714/699, 714/701, 714/709, 714/740, 714/799, 714/22, 323/222, 323/282
• US Class Current: 714/700
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators

Abstract

A method for controlling a variable of a switching electrical circuit detects values for each of a first waveform and of a second waveform in the switching circuit at a beginning of and at a predetermined instant during a switching interval of a switching operation of the electrical circuit, both of the first and second waveforms are perturbed by the switching operation, and evaluates the variable based on the corresponding values of both the first waveform and the second waveform detected at the beginning and at the predetermined instant during the switching interval. The method further adjusts an operating point of the circuit based on a change in the variable between the two evaluations so as to maximize the variable.

Claims

1. A method for controlling a variable of a switching electrical circuit, comprising the steps of:

(a) detecting values for each of a first waveform and of a second waveform in the switching circuit at a beginning of and at a predetermined instant during a switching interval of a switching operation of the electrical circuit, both of the first and second waveforms are perturbed by the switching operation;

(b) evaluating the variable based on the corresponding values of both the first waveform and the second waveform detected at the beginning and at the predetermined instant during the switching interval; and

(c) adjusting an operating point of the circuit based on a change in the variable between the two evaluations so as to minimize the change in the variable.

2. The method of claim 1, wherein the electrical circuit comprises a switching dc-dc converter.

3. The method of claim 2, wherein the first perturbed waveform is an input current of the converter.

4. The method of claim 3, wherein the predetermined instant is a switching instant of the switching operation of the electrical circuit.

5. The method of claim 2, wherein the second perturbed waveform is an input voltage of the converter.

6. The method of claim 5, wherein the predetermined instant is a switching instant of the switching operation of the electrical circuit augmented by a phase delay time.

7. The method of claim 2, wherein the variable to be controlled is a power input to the converter.

8. The method of claim 7, wherein the operating point is changed by varying a duty ratio of the converter.

9. The method of claim 2, wherein the operating point comprises an input voltage and an input current of the converter.

10. The method of claim 1, wherein the electrical circuit comprises an ac motor controller.

23. The method of claim 21, further comprising the step of:

repeating the steps of claim 1 after a third duration of time.

11. A controller for controlling a switching electrical circuit, comprising:

a first unit for detecting values of a first waveform perturbed by a switching operation of the electrical circuit at a beginning of and at a predetermined instant during a switching interval of the switching operation;

a second unit for detecting values of a second waveform perturbed by the switching operation of the electrical circuit at the beginning of and at the predetermined instant during the switching interval;

an evaluating unit coupled to the first and second units and operable to compute a variable to be controlled based on the corresponding values of both the first waveform and the second waveform detected at the beginning and at the predetermined instant during the switching interval; and

an operating point generator coupled to the evaluating unit and to the electrical circuit and operable to change an operating point of the electrical circuit based upon a change in the variable between the two evaluations.

12. The controller of claim 11, wherein the electrical circuit comprises a switching dc-dc converter.

13. The controller of claim 12, wherein the first perturbed waveform is an input current of the converter.

14. The controller of claim 12, wherein the second perturbed waveform is an input voltage of the converter.

15. The controller of claim 12, wherein the variable to be controlled is a power input to the converter.

16. The controller of claim 12, wherein the operating point comprises an input voltage and an input current of the converter.

17. The controller of claim 16, wherein the operating point generator is operable to vary a duty ratio of the converter.

18. A method for controlling an input power to a switching dc-dc converter, comprising the steps of:

(a) sensing a first ripple on an input voltage to the converter, the first ripple is produced by a switching operation of the converter, and detecting values of the input voltage at a beginning of and at a predetermined instant during a switching interval of the switching operation of the dc-dc converter;

(b) sensing a second ripple on an input current to the converter, the second ripple is produced by the switching operation of the converter, and detecting values of the input current at the beginning of and at the predetermined instant during the switching interval;

(c) evaluating the input power based on the corresponding values of both the input voltage and the input current detected at the beginning and at the predetermined instant during the switching interval; and

(d) varying a duty ratio of the switching operation based on a change in the input power so as to maximize or minimize the input power.

19. A computer readable storage medium comprising instructions which when executed by a computer system causes the computer to implement a method for controlling a variable of a switching electrical circuit, comprising:

a first unit for detecting values of a first waveform perturbed by a switching operation of the electrical circuit at a beginning of and at a predetermined instant during a switching interval of the switching operation;

a second unit for detecting values of a second waveform perturbed by the switching operation of the electrical circuit at the beginning of and at the predetermined instant during the switching interval;

an evaluating unit coupled to the first and second units and operable to compute the variable to be controlled based on the corresponding values of both the first waveform and the second waveform detected at the beginning and at the predetermined instant during the switching interval; and

an operating point generator coupled to the evaluating unit and to the electrical circuit and operable to change an operating point of the electrical circuit based upon a change in the variable between the two evaluations.

20. A system for performing a method for controlling a variable of a switching electrical circuit, the system comprising:

at least one processor programmed to detect values of a first waveform perturbed by a switching operation of the electrical circuit at a beginning of and at a predetermined instant during a switching interval of the switching operation;

at least one processor programmed to detect values of a second waveform perturbed by the switching operation of the electrical circuit at the beginning of and at the predetermined instant during the switching interval;

at least one processor programmed to compute the variable to be controlled based on the corresponding values of both the first waveform and the second waveform detected at the beginning and at the predetermined instant during the switching interval; and

at least one processor programmed to change an operating point of the electrical circuit based upon a change in the variable between the two evaluations.

21. A method for controlling an input power to a switching dc-dc converter, comprising the steps of:

turning the converter off for a first duration of time;

sensing an open circuit voltage to the converter and determining a target voltage based on the sensed open circuit voltage;

enabling a switching operation with a predetermined duty cycle and driving the input voltage of the controller to the target voltage;

sensing a first ripple on the input voltage to the converter after a second duration of time, the first ripple is produced by the switching operation of the converter, and detecting values of the input voltage at a beginning of and at a predetermined instant during a switching interval of the switching operation of the electrical circuit;

sensing a second ripple on an input current to the converter after the second duration of time, the second ripple is produced by the switching operation of the converter, and detecting values of the input current at the beginning of and at the predetermined instant during the switching interval;

evaluating the input power based on the corresponding values of both the input voltage and the input current detected at the beginning and at the predetermined instant during the switching interval; and

varying a duty ratio of the switching operation based on a change in the input power so as to minimize the change in the input power.

22. The method of claim 21, further comprising the step of:

maintaining the input voltage between a upper limit voltage and a lower limit voltage, which are both determined based on the open circuit voltage.

24. The method of claim 21, wherein the first duration of time is substantially greater than the second duration of time and the second duration of time is substantially greater than the third duration of time.

25. The method of claim 21, wherein the first duration of time is sufficient for the input current to become equal to zero and for the input voltage to reach the open circuit voltage.