Switching power converter with switch control pulse width variability at low power demand levels

• US 8,120,341 B2
• Filed: 05/02/2008
• Issued: 02/21/2012
• Est. Priority Date: 05/02/2007
• Status: Active Grant

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Melanson, John L.
• Primary Examiner(s): BERHANE, ADOLF D
• Application Number:
  US12/114,130
• Publication Number:
  US 20080272758A1
• Time in Patent Office: 1,390 Days
• Field of Search: 323282-285, 323/288, 323/351
• US Class Current: 323/282
• CPC Class Codes: H02M 1/4225 using a non-isolated boost converter
• CPC Class Codes: H03M 3/476 Non-linear conversion systems
• 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
• CPC Class Codes: Y02P 80/10 Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier

Abstract

A power control system includes a switch mode controller to control the switching mode of a switching power converter. The switch mode controller generates a switch control signal that controls conductivity of a switch of the switching power converter. Controlling conductivity of the switch controls the switch mode of the switching power converter. The switch mode controller includes a period generator to determine a period of the switch control signal and to vary the determined period to generate a broad frequency spectrum of the switch control signal when the determined period corresponds with a frequency in at least a portion of an audible frequency band. Generating a switch control signal with a broad frequency spectrum in the audible frequency band allows the system to utilize switching frequencies in the audible frequency band.

Claims

1. A system comprising:

a switch mode controller to generate a switch control signal to control conductivity of a switching mode switch included in a switching power converter, wherein the switch mode controller comprises;

a period generator to determine a nominal period of the switch control signal, recognize when the nominal period corresponds with a frequency in at least a portion of an audible frequency band, and to vary the nominal period to generate a broad frequency spectrum of the switch control signal when the nominal period corresponds with a frequency in at least a portion of an audible frequency band.

2. The system of claim 1 wherein the period generator is further configured to generate a broad frequency spectrum of the switch control signal having randomly selected periods.

3. The system of claim 1 wherein an average of the randomly selected periods approximately equals the nominal period.

4. The system of claim 1 wherein the period generator further comprises a pseudo random number generator to generate pseudorandom numbers, and the period generator is further configured to generate a broad frequency spectrum of the switch control signal having randomly selected periods based on the pseudorandom numbers.

5. The system of claim 1 wherein the period generator is further configured to generate the broad frequency spectrum of the switch control signal using periods determined using low pass filtered, pseudo random numbers.

6. The system of claim 1 wherein the period generator is further configured to generate the broad frequency spectrum of the switch control signal using periods determined using high pass filtered, pseudo random numbers.

7. The system of claim 1 wherein the period generator is further configured to generate the broad frequency spectrum of the switch control signal using delta-sigma modulated, randomized values of the nominal period.

8. The system of claim 1 wherein the audible frequency band is approximately 20 Hz to 20 kHz.

9. The system of claim 1 wherein the switch mode controller is further configured to control conductivity of the switch mode switch to cause an input current to the switching power converter to vary in approximate proportion to a time varying voltage source signal supplied to the switching power converter, wherein the switch mode controller further comprises:

a pulse width generator to determine a pulse width of the switch control signal in response to (i) the nominal period of the switch control signal, (ii) a voltage level of the voltage source signal, and (iii) a voltage level of the output voltage signal of the switching power converter.

26. The system of claim 1 wherein the period generator is further configured to:

shape the broad frequency spectrum to minimize power in frequencies within particularly sensitive areas of the audible frequency band.

27. The system of claim 26 wherein the frequencies within particularly sensitive areas of the audible frequency band are from approximately 1 kHz-20 kHz.

32. The apparatus of claim 1 further comprising:

means for shaping the broad frequency spectrum to minimize power in frequencies within particularly sensitive areas of the audible frequency band.

33. The apparatus of claim 32 wherein the frequencies within particularly sensitive areas of the audible frequency band are from approximately 1 kHz-20 kHz.

10. A method comprising:

generating a switch control signal to control conductivity of a switch mode switch included in a switching power converter;

determining a nominal period of the switch control signal;

recognizing when the nominal period corresponds with a frequency in at least a portion of an audible frequency band,

varying the nominal period to generate a broad frequency spectrum of the switch control signal when the nominal period corresponds with a frequency in at least a portion of an audible frequency band;

determining a pulse width of the switch control signal; and

providing the switch control signal to the switch of the switching power converter.

11. The method of claim 10 further comprising:

controlling conductivity of the switch to cause an input current to the switching power converter to vary in approximate proportion to a time varying voltage source signal supplied to the switching power converter; and

determining a pulse width of the switch control signal further comprises determining a pulse width of the switch control signal in response to (i) the nominal period of the switch control signal, (ii) a voltage level of the voltage source signal, and (iii) a voltage level of the output voltage signal of the switching power converter.

12. The method of claim 10 wherein varying the nominal period to generate a broad frequency spectrum of the switch control signal further comprises generating a broad frequency spectrum of the switch control signal having randomly selected periods.

13. The method of claim 12 wherein an average of the randomly selected periods approximately equals the nominal period.

14. The method of claim 10 wherein varying the nominal period to generate a broad frequency spectrum of the switch control signal further comprises generating pseudorandom numbers and generating a broad frequency spectrum of the switch control signal having randomly selected periods based on the pseudorandom numbers.

15. The method of claim 10 wherein varying the nominal period to generate a broad frequency spectrum of the switch control signal further comprises generating the broad frequency spectrum of the switch control signal using periods determined using low pass filtered, pseudo random numbers.

16. The method of claim 10 wherein varying the nominal period to generate a broad frequency spectrum of the switch control signal further comprises generating the broad frequency spectrum of the switch control signal using periods determined using high pass filtered, pseudo random numbers.

17. The method of claim 10 wherein varying the nominal period to generate a broad frequency spectrum of the switch control signal further comprises generating the broad frequency spectrum of the switch control signal using delta-sigma modulated, randomized values of the nominal period.

18. The method of claim 10 wherein the audible frequency band is approximately 20 Hz to 20 kHz.

19. The method of claim 10 further comprising:

controlling conductivity of the switch to cause an input current to the switching power converter to vary in approximate proportion to a time varying voltage source signal supplied to the switching power converter; and

determining a pulse width of the switch control signal further comprises determining a pulse width of the switch control signal in response to (i) the nominal period of the switch control signal, (ii) a voltage level of the voltage source signal, and (iii) a voltage level of the output voltage signal of the switching power converter.

28. The method of claim 10 further comprising:

shaping the broad frequency spectrum to minimize power in frequencies within particularly sensitive areas of the audible frequency band.

29. The method of claim 28 wherein the frequencies within particularly sensitive areas of the audible frequency band are from approximately 1 kHz-20 kHz.

20. A power control system comprising:

a switching power converter having a switch; and

a switch mode controller to generate a switch control signal to control conductivity of a switching mode switch included in a switching power converter, wherein the switch mode controller comprises;

a period generator to determine a nominal period of the switch control signal, recognize when the nominal period corresponds with a frequency in at least a portion of an audible frequency band, and to vary the nominal period to generate a broad frequency spectrum of the switch control signal when the nominal period corresponds with a frequency in at least a portion of an audible frequency band.

21. The power control system of claim 20 wherein the period generator is further configured to generate a broad frequency spectrum of the switch control signal having randomly selected periods.

22. The power control system of claim 20 wherein the switching power converter further includes an input node, an inductor coupled to the input node and the switch, a diode coupled to the switch and the inductor, and an output capacitor coupled to the diode.

23. The power control system of claim 20 wherein the switch mode controller is further configured to control conductivity of the switch mode switch to cause an input current to the switching power converter to vary in approximate proportion to a time varying voltage source signal supplied to the switching power converter, wherein the switch mode controller further comprises:

a pulse width generator to determine a pulse width of the switch control signal in response to (i) the nominal period of the switch control signal, (ii) a voltage level of the voltage source signal, and (iii) a voltage level of the output voltage signal of the switching power converter.

30. The power control system of claim 21 wherein the period generator is further configured to:

shape the broad frequency spectrum to minimize power in frequencies within particularly sensitive areas of the audible frequency band.

31. The power control system of claim 30 wherein the frequencies within particularly sensitive areas of the audible frequency band are from approximately 1 kHz-20 kHz.

24. An apparatus comprising:

means for generating a switch control signal to control conductivity of a switch mode switch included in a switching power converter;

means for determining a nominal period of the switch control signal;

means for recognizing when the nominal period corresponds with a frequency in at least a portion of an audible frequency band,

means for varying the nominal period to generate a broad frequency spectrum of the switch control signal when the nominal period corresponds with a frequency in at least a portion of an audible frequency band;

means for determining a pulse width of the switch control signal; and

means for providing the switch control signal to the switch of the switching power converter.

25. The apparatus of claim 24 further comprising:

means for controlling conductivity of the switch to cause an input current to the switching power converter to vary in approximate proportion to a time varying voltage source signal supplied to the switching power converter; and

means for determining a pulse width of the switch control signal further comprises determining a pulse width of the switch control signal in response to (i) the nominal period of the switch control signal, (ii) a voltage level of the voltage source signal, and (iii) a voltage level of the output voltage signal of the switching power converter.