Adaptive control for inducer based buck-boost voltage regulators

• US 7,265,524 B2
• Filed: 09/14/2004
• Issued: 09/04/2007
• Est. Priority Date: 09/14/2004
• Status: Active Grant

• Current Assignee: Analog Devices International Unlimited Company (Analog Devices, Inc.)
• Original Assignee: Linear Technology Corporation (Analog Devices, Inc.)
• Inventors: Wells, James Edward, Jordan, Mark G.
• Primary Examiner(s): Han; Jessica
• Application Number:
  US10/939,469
• Publication Number:
  US 20060055384A1
• Time in Patent Office: 1,085 Days
• Field of Search: 323/222, 323/224, 323/225, 323/282, 323/284, 323/290, 323/259, 323/351
• US Class Current: 323/225
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H02M 3/1582 Buck-boost converters H02M3/1584 takes precedence

Abstract

Voltage regulators and methods for regulating voltages are disclosed. A switching circuit with an inductor and a plurality of switches may be used to produce a regulated voltage from an unregulated voltage source. A control circuit may be used to monitor the voltages at the input and output of the voltage regulator, and operate the switches in either a buck, boost, or buck-boost mode depending on the relationship between the voltages at the input and output of the voltage regulator.

Claims

1. A voltage regulator having an input and output, comprising:

a switching circuit having an inductive element and switches configured to switch the inductive element to the input and output of the voltage regulator; and

a control circuit configured to operate the switches in a buck, boost, or buck-boost mode,

wherein the control circuit is responsive to a signal indicating whether the voltage regulator is in the buck, boost or buck-boost mode to determine timing of the switches in accordance with current in the inductive element, and

the control circuit is further configured to set the switches into predetermined states so as to place the voltage regulator into a sleep mode in response to a rise in the output voltage of the voltage regulator beyond a threshold voltage.

2. The voltage regulator of claim 1 wherein the control circuit is further configured to operate the switches in cycles in each of the buck, boost and buck-boost modes, each of the cycles having a first phase with the inductive element coupled to the input, followed by a second phase with the inductive element coupled to the output, with the input of the voltage regulator being coupled to the output of the voltage regulator through the inductive element during a portion of each of the cycles.

3. The voltage regulator of claim 2 wherein the duration of the first and second phases of each of the cycles is a function of the current flowing through the inductive element.

4. The voltage regulator of claim 2 wherein the control circuit is further configured to operate the switches to couple the input of the voltage regulator to the output of the voltage regulator through the inductive element during the first phase of each of the cycles in the buck mode, and operate the switches to couple the input of the voltage regulator to the output of the voltage regulator through the inductive element during the second phase of each of the cycles in the boost mode.

5. The voltage regulator of claim 2 wherein the second phase of each of the cycles comprises a first portion followed by a second portion, the control circuit being further configured to operate the switches to couple the input of the voltage regulator to the output of the voltage regulator during the first portion of the second phase of each of the cycles in the buck-boost mode.

6. The voltage regulator of claim 5 wherein the control circuit is further configured to operate the switches to terminate the first portion of the second phase of each of the cycles when a fixed time duration from the beginning of the second phase expires or the current flowing through the inductive element reaches a threshold current, whichever occurs first following the beginning of the second phase.

7. The voltage regulator of claim 5 wherein the control circuit is further configured to operate the switches to terminate the first portion of the second phase of each of the cycles when a fixed time duration from the beginning of the second phase expires, the current flowing through the inductive element drops to a first threshold current, or the current flowing through the inductive element reaches a second threshold current higher than the first threshold current, whichever occurs first following the beginning of the second phase.

8. The voltage regulator of claim 2 wherein the control circuit is further configured to operate the switches to terminate the first phase of each of the cycles when the current flowing through the inductive element reaches a threshold current.

9. The voltage regulator of claim 8 wherein the threshold current is adjustable.

10. The voltage regulator of claim 8 wherein the control circuit is further configured to operate the switches to terminate the second phase of each of the cycles when the current flowing through the inductive elements falls to a second threshold current lower than the threshold current.

11. The voltage regulator of claim 10 wherein the second threshold current level is zero current.

12. The voltage regulator of claim 8 wherein the control circuit is further configured to operate the switches such that the second phase of each of the cycles has a fixed time duration.

13. The voltage regulator of claim 1 wherein the inductive element comprises an inductor.

14. A method of operating a voltage regulator to produce a regulated voltage at its output from a voltage source, the voltage regulator having an inductive element, the method comprising:

transferring energy from the voltage source to the output of the voltage regulator using an inductive element and switches in a buck, boost or buck-boost mode;

in response to determining whether the energy is transferred in the buck, boost or buck-boost mode, determining timing of the switches in accordance with current in the inductive element;

detecting a rise in the output voltage of the voltage regulator beyond a threshold voltage; and

setting the switches into predetermined states so as to force the voltage regulator into a sleep mode only in response to the detected rise in the output voltage of the voltage regulator beyond the threshold voltage.

15. The method of claim 14 wherein the energy is transferred from the voltage source to the output of the voltage regulator in cycles in each of the buck, boost, and buck-boost modes, each of the cycles having a first phase followed by a second phase, and wherein the energy is transferred from the voltage source to the output of the voltage regulator by coupling the voltage source to the inductive element during the first phase of each of the cycles, and coupling the inductive element to the output of the voltage regulator during the second phase of each of the cycles, with the voltage source being coupled to the output of the voltage regulator through the inductive element during a portion of each of the cycles.

16. The method of claim 15 wherein the duration of the first and second phases of each of the cycles is a function of the current flowing through the inductive element.

17. The method of claim 15 wherein the voltage source is coupled to the output of the voltage regulator through the inductive element during the first phase of each of the cycles in the buck mode, and the voltage source is coupled to the output of the voltage regulator through the inductive element during the second phase of each of the cycles in the boost mode.

18. The method of claim 15 wherein the energy is transferred from the voltage source to the output of the voltage regulator by terminating the first phase of each of the cycles when the current flowing through the inductive element reaches a threshold current.

19. The method of claim 18 further comprising adjusting the threshold current.

20. The method of claim 18 wherein the energy is transferred from the voltage source to the output of the voltage regulator by terminating the second phase of each of the cycles when the current flowing through the inductive element falls to a second threshold current lower than the threshold current.

21. The method of claim 20 wherein the second threshold current is zero current.

22. The method of claim 18 wherein the energy is transferred from the voltage source to the output of the voltage regulator during the second phase of each of the cycles having a fixed time duration.

23. The method of claim 14 wherein the inductive element comprises an inductor.

24. The method of claim 14 wherein the energy is transferred from the voltage source to the output of the voltage regulator in cycles, each of the cycles including a first phase with the voltage source coupled to the inductive element followed by a second phase with the inductive element coupled to the output of the voltage regulator, the second phase of each of the cycles having a first portion with the voltage source coupled to the output of the voltage regulator through the inductive element followed by a second portion.

25. The method of claim 24 wherein the energy is transferred from the voltage source to the output of the voltage regulator by terminating the first portion of the second phase of each of the cycles when a fixed time duration from the beginning of the second phase expires or the current flowing through the inductive element reaches a threshold current, whichever occurs first following the beginning of the second phase.

26. The method of claim 24 wherein the energy is transferred from the voltage source to the output of the voltage regulator by terminating the first portion of the second phase of each of the cycles when a fixed time duration from the beginning of the second phase expires, the current flowing through the inductive element falls to a first threshold current, or the current flowing through the inductive element reaches a second threshold current higher than the first threshold current, whichever occurs first following the beginning of the second phase.

27. A voltage regulator having an input and output, comprising:

a switching circuit having an inductive element and switches configured to switch the inductive element to the input and output of the voltage regulator; and

a control circuit comprising means for operating the switches in buck, boost, or buck-boost mode,

wherein the control circuit is responsive to a signal indicating whether the voltage regulator is in the buck, boost or buck-boost mode to determine timing of the switches in accordance with current in the inductive element, and

the control circuit is further configured to set the switches into predetermined states so as to place the voltage regulator into a sleep mode in response to a rise in the output voltage of the voltage regulator beyond a threshold voltage.

28. A voltage regulator having an input and output, comprising:

a switching circuit having an inductive element, and switches including a first switch between the input of the voltage regulator and one end of the inductive element, a second switch between the one end of the inductive element and a voltage return line, a third switch between the other end of the inductive element and the voltage return line, and a fourth switch between the other end of the inductive element and the output of the voltage regulator; and

a control circuit having a mode controller configured to operate the switches in buck, boost, or buck-boost mode,

wherein the control circuit is responsive to the mode controller indicating whether the voltage regulator is in the buck, boost or buck-boost mode to determine timing of the switches in accordance with current in the inductive element, and

the control circuit is further configured to set the switches into predetermined states so as to place the voltage regulator into a sleep mode in response to a rise in the output voltage of the voltage regulator beyond a threshold voltage.

29. The voltage regulator of claim 28 wherein the switching circuit further comprises an inductive element current sensor, and wherein the control circuit is further configured to operate the switches in cycles, each of the cycles having a first phase with the first switch closed, followed by a second phase with the fourth switch closed, with the first and fourth switches being closed at the same time during a portion of each of the cycles, and wherein the duration of the first and second phases of each of the cycles is a function of the current sensed by the inductive element current sensor.

30. The voltage regulator of claim 29 wherein the control circuit is further configured to close the fourth switch during both the first and second phases of each of the cycles in the buck mode, and close the first switch during both the first and second phases of each of the cycles in the boost mode.

31. The voltage regulator of claim 29 wherein the second phase of each of the cycles comprises a first portion followed by a second portion, the control circuit being further configured to close both the first and fourth switches during the first portion of the second phase of each of the cycles in the buck-boost mode.

32. The voltage regulator of claim 31 wherein the control is further configured to close the third switch during the first phase of each of the cycles in the buck-boost mode, and close the second switch during the second portion of the second phase of each of the cycles during the buck-boost mode.

33. The voltage regulator of claim 32 wherein the control circuit is further configured to open the second and fourth switches during the first phase of each of the cycles during the buck-boost mode, open the second and third switches during the first portion of the second phase of each of the cycles during the buck-boost mode, and open the first and third switches during the second portion of the second phase of each of the cycles during the buck-boost mode.

34. The voltage regulator of claim 28 wherein the inductive element comprises an inductor.

35. A voltage regulator having an input and output, comprising:

a switching circuit having an inductive element and switches configured to switch the inductive element to the input and output of the voltage regulator; and

a control circuit configured to operate the switches in a buck-boost mode,

wherein the control circuit is responsive to a signal indicating that the voltage regulator is in the buck-boost mode to determine timing of the switches in accordance with current in the inductive element, and

the control circuit is further configured to set the switches into predetermined states so as to place the voltage regulator into a sleep mode in response to a rise in the output voltage of the voltage regulator beyond a threshold voltage.

36. The voltage regulator of claim 35 wherein the control circuit is further configured to operate the switches in cycles, each of the cycles having a first phase with the inductive element coupled to the input of the voltage regulator, followed by a second phase with the inductive element coupled to the output of the voltage regulator, the second phase of each of the cycles having a first portion with the input of the voltage regulator coupled to the output of the voltage regulator through the inductive element followed by a second portion.

37. The voltage regulator of claim 36 wherein the duration of the first and second phases of each of the cycles is a function of the current flowing through the inductive element.

38. The voltage regulator of claim 36 wherein the control circuit is further configured to operate the switches to terminate the first portion of the second phase of each of the cycles when a fixed time duration from the beginning of the second phase expires or the current flowing through the inductive element reaches a threshold current, whichever occurs first following the beginning of the second phase.

39. The voltage regulator of claim 36 wherein the control circuit is further configured to operate the switches to terminate the first portion of the second phase of each of the cycles when a fixed time duration from the beginning of the second phase expires, the current flowing through the inductive element drops to a first threshold current, or the current flowing through the inductive element reaches a second threshold current higher than the first threshold current, whichever occurs first following the beginning of the second phase.

40. The voltage regulator of claim 36 wherein the control circuit is further configured to operate the switches to terminate the first phase of each of the cycles when the current flowing through the inductive element reaches a threshold current.

41. The voltage regulator of claim 40 wherein the threshold current is adjustable.

42. The voltage regulator of claim 40 wherein the control circuit is further configured to operate the switches to terminate the second phase of each of the cycles when the current flowing through the inductive elements falls to a second threshold current lower than the threshold current.

43. The voltage regulator of claim 42 wherein the second threshold current is zero current.

44. The voltage regulator of claim 36 wherein the control circuit is further configured to operate the switches such that the second phase of each of the cycles has a fixed time duration.

45. The voltage regulator of claim 35 wherein the inductive element comprises an inductor.