Adaptive digital control of power factor correction front end

• US 8,654,553 B1
• Filed: 03/15/2013
• Issued: 02/18/2014
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Flextronics America LLC (Flextronics International Limited)
• Original Assignee: Flextronics America LLC (Flextronics International Limited)
• Inventors: Ye, Zhen Z., Dunn, Jamie
• Primary Examiner(s): Tran, Nguyen
• Application Number:
  US13/835,781
• Time in Patent Office: 340 Days
• Field of Search: 363/40, 363/84, 363/88, 363/89, 363/90, 363/95, 363/97, 323/207
• US Class Current: 363/89
• CPC Class Codes: H02M 1/0012 Control circuits using digital or numerical techniques in DC/DC converters H02M3/157, H02M3/33515; in DC-AC converters H02M7/53873
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/12 Arrangements for reducing harmonics from ac input or output
• CPC Class Codes: H02M 1/4208 Arrangements for improving power factor of AC input
• CPC Class Codes: H02M 3/24 by static converters
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A method is directed to providing adaptive digital control for the PFC front-end of a switching mode power supply. The method uses an evaluation model to adjust control loop parameters of a control algorithm used by a controller on the primary side of the power supply. The method performs a series of step adjustments of the control loop parameter values to determine optimized values. In some implementations, the method determines and compares the line current THD corresponding to different control loop parameter values. The method provides simplified digital control loop design, optimizes PFC front-end performance, improves system efficiency by decreasing harmonic ripples, and reduces labor cost and time to market due to shorter research and development phase. System performance optimization is fully adaptive adjusted for changes in operating conditions due to, for example, environmental and temperature variations.

Claims

1. A method of adaptively controlling a power supply, the method comprising:

a. configuring a switching mode power supply to include a transformer having a primary side and a secondary side, a primary side circuit under control of a primary side controller and a secondary side circuit under control of a secondary side controller, wherein the primary side controller controls the primary side circuit using a control algorithm that includes control loop parameters;

b. setting the control loop parameters to default control loop parameter values;

c. determining line current total harmonic distortion corresponding to the default control loop parameter values;

d. adjusting the control loop parameters;

e. determining line current total harmonic distortion corresponding to the adjusted control loop parameters;

f. comparing the line current total harmonic distortion corresponding to the adjusted control loop parameters to the line current total harmonic distortion corresponding to the default control loop parameter values to determine a lowest line current total harmonic distortion;

g. setting optimized control loop parameters using the control loop parameters corresponding to the lowest line current total harmonic distortion; and

h. executing the control algorithm using the optimized control loop parameters.

2. The method of claim 1 wherein determining line current total harmonic distortion comprises measuring a line current and applying a Fast Fourier Transform to the measured line current.

3. The method of claim 2 wherein determining line current total harmonic distortion further comprises performing a power spectral density analysis on the Fast Fourier Transform result.

4. The method of claim 1 wherein determining line current total harmonic distortion comprises passing a line current through a set of band pass filters.

5. The method of claim 1 wherein adjusting the control loop parameters comprises increasing or decreasing each control loop parameter by a predefined increment.

6. The method of claim 1 wherein the primary side circuit is configured for power factor correction and AC-to-DC voltage conversion.

7. The method of claim 1 wherein the secondary side circuit is configured for DC-to-DC voltage conversion.

8. A method of adaptively controlling a power supply, the method comprising:

a. configuring a switching mode power supply to include a transformer having a primary side and a secondary side, a primary side circuit under control of a primary side controller and a secondary side circuit under control of a secondary side controller, wherein the primary side controller controls the primary side circuit using a control algorithm that includes control loop parameters;

b. setting the control loop parameters to default control loop parameter values;

c. determining line current total harmonic distortion corresponding to the default control loop parameter values;

d. adjusting the control loop parameters;

e. determining line current total harmonic distortion corresponding to the adjusted control loop parameters;

f. comparing the line current total harmonic distortion corresponding to the adjusted control loop parameters to the line current total harmonic distortion corresponding to the default control loop parameter values to determine a lowest line current total harmonic distortion;

g. setting improved control loop parameters using the control loop parameters corresponding to the lowest line current total harmonic distortion;

h. performing one or more iterations of adjusting the improved control loop parameters for a present iteration, determining a resulting line current total harmonic distortion corresponding to the present iteration, comparing the resulting line current total harmonic distortion of the present iteration to the determined line current total harmonic distortion corresponding to the improved control loop parameters of a previous iteration, and resetting the improved control loop parameters using the control loop parameters corresponding to the lowest line current total harmonic distortion, wherein the one or more iterations are repeated until an optimized criteria is achieved and the improved control loop parameters are set as optimized control loop parameters; and

i. executing the control algorithm using the optimized control loop parameters.

9. The method of claim 8 wherein determining line current total harmonic distortion comprises measuring a line current and applying a Fast Fourier Transform to the measured line current.

10. The method of claim 9 wherein determining line current total harmonic distortion further comprises performing a power spectral density analysis on the Fast Fourier Transform result.

11. The method of claim 8 wherein determining line current total harmonic distortion comprises passing a line current through a set of band pass filters.

12. The method of claim 8 wherein the optimized criteria comprises determining that the determined line current total harmonic distortion is less than a line current total harmonic distortion minimum threshold value.

13. The method of claim 8 wherein adjusting the improved control loop parameters for the present iteration comprises increasing or decreasing each improved control loop parameter by a predefined increment.

14. The method of claim 13 wherein the optimized criteria is achieved when a minimum line current total harmonic distortion is determined through successive incrementing and decrementing of the improved control loop parameters.

15. The method of claim 8 wherein adjusting the control loop parameters comprises increasing or decreasing each control loop parameter by a predefined increment.

16. The method of claim 8 wherein the primary side circuit is configured for power factor correction and AC-to-DC voltage conversion.

17. The method of claim 8 wherein the secondary side circuit is configured for DC-to-DC voltage conversion.

18. An apparatus for adaptively controlling a power supply, the apparatus comprising:

a. a switching mode power supply comprising a transformer having a primary side circuit and a secondary side circuit; and

b. a primary side controller configured to control the primary side circuit using a control algorithm that includes control loop parameters, wherein the control algorithm is configured to;

i. setting the control loop parameters to default control loop parameter values;

ii. determining line current total harmonic distortion corresponding to the default control loop parameter values;

iii. adjusting the control loop parameters;

iv. determining line current total harmonic distortion corresponding to the adjusted control loop parameters;

v. comparing the line current total harmonic distortion corresponding to the adjusted control loop parameters to the line current total harmonic distortion corresponding to the default control loop parameter values to determine a lowest line current total harmonic distortion;

vii. setting optimized control loop parameters using the control loop parameters corresponding to the lowest line current total harmonic distortion; and

viii. executing the control algorithm using the optimized control loop parameters.

19. The apparatus of claim 18 further comprising a secondary side controller configured to control the secondary side circuit.

20. The apparatus of claim 18 wherein the control algorithm is further configured to perform one or more iterations of adjusting the improved control loop parameters for a present iteration, determine a resulting line current total harmonic distortion corresponding to the present iteration, compare the resulting line current total harmonic distortion of the present iteration to the determined line current total harmonic distortion corresponding to the improved control loop parameters of a previous iteration, and reset the improved control loop parameters using the control loop parameters corresponding to the lowest line current total harmonic distortion, wherein the one or more iterations are repeated until an optimized criteria is achieved and the improved control loop parameters are set as optimized control loop parameters.

21. The apparatus of claim 18 wherein the primary side controller is configured to determine line current total harmonic distortion by measuring a line current and applying a Fast Fourier Transform to the measured line current.

22. The apparatus of claim 21 wherein the primary side controller is further configured to determine line current total harmonic distortion by performing a power spectral density analysis on the Fast Fourier Transform result.

23. The apparatus of claim 18 wherein the apparatus further comprises a set of band pass filters and the primary side controller is configured to determine line current total harmonic distortion by passing a line current through the set of band pass filters.

24. The apparatus of claim 18 wherein the primary side controller is configured to adjust the control loop parameters by increasing or decreasing each control loop parameter by a predefined increment.

25. The apparatus of claim 18 wherein the primary side circuit is configured for power factor correction and AC-to-DC voltage conversion.

26. The apparatus of claim 18 wherein the secondary side circuit is configured for DC-to-DC voltage conversion.