Switching Circuits For Extracting Power From An Electric Power Source And Associated Methods

• US 20120043823A1
• Filed: 08/17/2011
• Published: 02/23/2012
• Est. Priority Date: 08/18/2010
• Status: Active Grant

• Current Assignee: Volterra Semiconductor Corporation (Analog Devices, Inc.)
• Original Assignee: Volterra Semiconductor Corporation (Analog Devices, Inc.)
• Inventors: Stratakos, Anthony J., McJimsey, Michael D., Jergovic, Ilija, Ikriannikov, Alexandr, Yao, Kaiwei, Lidsky, David B., Zuniga, Marco A., Borisavljevic, Ana, Der Minassians, Artin
• Granted Patent: US 9,035,626 B2
• Time in Patent Office: Days
• US Class Current: 307/82
• CPC Class Codes: H01L 2224/16225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48227 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/13091 Metal-Oxide-Semiconductor Field-Effect Transistor [MOSFET]
• CPC Class Codes: H02J 1/102 being switching converters H02J1/108, H02J1/12 take precedence
• CPC Class Codes: H02J 1/106 for load balancing, symmetrisation, or sharing
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H03K 17/102 in field-effect transistor switches
• CPC Class Codes: H03K 17/122 in field-effect transistor switches
• CPC Class Codes: H03K 17/145 in field-effect transistor switches
• CPC Class Codes: H03K 17/693 Switching arrangements with several input- or output-terminals, e.g. multiplexers, distributors logic circuits H03K19/00; code converters H03M5/00, H03M7/00
• CPC Class Codes: H03K 2217/0036 Means reducing energy consumption
• CPC Class Codes: H03K 2217/0054 Gating switches, e.g. pass gates
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

A switching circuit for extracting power from an electric power source includes (1) an input port for electrically coupling to the electric power source, (2) an output port for electrically coupling to a load, (3) a first switching device configured to switch between its conductive state and its non-conductive state to transfer power from the input port to the output port, (4) an intermediate switching node that transitions between at least two different voltage levels at least in part due to the first switching device switching between its conductive state and its non-conductive state, and (5) a controller for controlling the first switching device to maximize an average value of a voltage at the intermediate switching node.

Claims

1. A switching circuit for extracting power from an electric power source, comprising:

an input port for electrically coupling to the electric power source;

an output port for electrically coupling to a load;

a first switching device configured to switch between its conductive state and its non-conductive state to transfer power from the input port to the output port;

an intermediate switching node that transitions between at least two different voltage levels at least in part due to the first switching device switching between its conductive state and its non-conductive state; and

a controller for controlling the first switching device to maximize an average value of a voltage at the intermediate switching node.

2. The switching circuit of claim 1, wherein the controller is adapted to repeatedly sample the average value of the voltage at the intermediate switching node and control switching of the first switching device at least partly based on at least two successive samples of the average value of the voltage at the intermediate switching node.

3. The switching circuit of claim 2, wherein the controller is adapted to control switching of the first switching device in response to a difference between two successive samples of the average value of the voltage at the intermediate switching node.

4. The switching circuit of claim 3, wherein the controller is adapted to control switching of the first switching device in response to a sign of the difference between two successive samples of the average value of the voltage at the intermediate switching node.

5. The switching circuit of claim 3, wherein the controller is adapted to control switching of the first switching device in response to a magnitude of the difference between two successive samples of the average value of the voltage at the intermediate switching node.

6. The switching circuit of claim 3, wherein the controller is configured to control switching of the first switching device in response to both a sign and a magnitude of the difference between two successive samples of the average value of the voltage at the intermediate switching node.

7. The switching circuit of claim 2, wherein the controller comprises a sampling circuit configured to generate the at least two successive samples of the average value of the voltage at the intermediate switching node.

8. The switching circuit of claim 7, wherein the sampling circuit comprises a first and a second sampling circuit, the first sampling circuit configured to sample the average value of the voltage at the intermediate switching node at a different time than the second sampling circuit.

9. The switching circuit of claim 8, wherein the controller further comprises a first and a second low pass filter, the first low pass filter configured to generate an average value of the voltage at the intermediate switching node for the first sampling circuit, the second low pass filter configured to generate an average value of the voltage at the intermediate switching node for the second sampling circuit, each of the first and second low pass filters having a respective time constant greater than a switching period of the first switching device.

10. The switching circuit of claim 9, wherein the first and second low pass filters share at least one component.

11. The switching circuit of claim 7, wherein a starting time of the switching circuit controller is loosely controlled.

12. The switching circuit of claim 2, wherein the controller is configured to repeatedly sample the average value of the voltage at the intermediate switching node at a sampling rate that is sufficiently fast such that a percentage change in current out of the output port is less than a percentage change in duty cycle of the first switching device between successive samples of the average value of the voltage at the intermediate switching node.

13. The switching circuit of claim 2, wherein the controller is configured to repeatedly sample the average value of the voltage at the intermediate switching node at a sampling rate that is sufficiently fast such that Δ

I/I_R is less than Δ

D/D_R, wherein;

Δ

I is a change in current out of the output port between first and second successive samples of the average value of the voltage at the intermediate switching node, the second sample occurring after the first sample;

I_R=I_max−

I_min;

I_max is a maximum expected value of current out of the output port;

I_min is a minimum expected value of current out of the output port;

Δ

D is a change in duty cycle of the first switching device between the first and second successive samples of the average value of the voltage at the intermediate switching node; and

D_R is a difference between a maximum expected duty cycle and a minimum expected duty cycle of the first switching device.

14. The switching circuit of claim 2, wherein the controller is adapted to repeatedly sample the average value of the voltage at the intermediate switching node at a frequency that is less than a frequency at which the first switching device switches between its conductive and non-conductive states.

15. The switching circuit of claim 14, wherein the controller is adapted to repeatedly sample the average value of the voltage at the intermediate switching node at a frequency that is less than one tenth of the frequency at which the first switching device switches between its conductive and non-conductive states.

16. The switching circuit of claim 1, wherein:

the input port comprises a first and a second input terminal;

the output port comprises a first and a second output terminal;

the first switching device is electrically coupled between the first input terminal and the intermediate switching node; and

the switching circuit further comprises a device selected from the group consisting of a second switching device and a diode electrically coupled between the second input terminal and the intermediate switching node, the device configured to provide a path for current between the first and second output terminals when the first switching device is in its non-conductive state.

17. The switching circuit of claim 16, wherein the first output terminal is electrically coupled to the intermediate switching node, and the second output terminal is electrically coupled to the second input terminal.

18. The switching circuit of claim 1, wherein:

the input port comprises a first and a second input terminal;

the output port comprises a first and a second output terminal;

the first switching device is electrically coupled between the first input terminal and the intermediate switching node; and

the switching circuit further comprises a second switching device and a diode each electrically coupled between the second input terminal and the intermediate switching node, the second switching device and the diode configured to provide a path for current between the first and second output terminals when the first switching device is in its non-conductive state.

19. The switching circuit of claim 1, wherein:

the switching circuit further comprises a bias power supply port;

the input port comprises a first and a second input terminal; and

the controller is configured to be at least partially powered from an electric power source electrically coupled to the bias power supply port when a magnitude of a voltage across the second and first input terminals is below a threshold value.

20. The switching circuit of claim 1, the first switching device comprising a transistor including a plurality of individually controllable transistor elements, wherein at least some of the individually controllable transistor elements are operable to be individually switched between their conductive and non-conductive states, the controller configured to control an active number of the plurality of individually controllable transistor elements at least partially based on a duty cycle of the first switching device.

21. The switching circuit of claim 1, wherein:

the switching circuit further comprises a second switching device configured to switch between its conductive and non-conductive states and to cooperate with the first switching device to transfer power from the input port to the output port; and

the second switching device comprises a transistor including a plurality of individually controllable transistor elements, where at least some of the individually controllable transistor elements are operable to be individually switched between their conductive and non-conductive states, the controller configured to control an active number of the plurality of individually controllable transistor elements at least partially based on a duty cycle of the second switching device.

22. The switching circuit of claim 1, wherein:

the controller is adapted to control the first switching device to maximize the average value of the voltage at the intermediate switching node in a first operating mode of the switching circuit;

the controller is further adapted to continuously operate the first switching device in its non-conductive state in a second operating mode of the switching circuit;

the output port comprises a first and a second output terminal;

the switching circuit further comprises a device electrically coupled between the first and second output terminals and adapted to provide a path for current between the first and second output terminals when the first switching device is in its non-conductive state.

23. The switching circuit of claim 22, wherein the controller is further configured to operate the switching circuit in the second operating mode if a magnitude of a voltage of an electric power source powering the controller is less than or equal to a threshold voltage.

24. The switching circuit of claim 23, wherein the device electrically coupled between the first and second output terminals comprises a diode.

25. The switching circuit of claim 23, wherein the device electrically coupled between the first and second output terminals comprises a depletion mode transistor.

26. The switching circuit of claim 1, wherein:

the output port comprises a first and a second output terminal;

the switching circuit further comprises a second switching device electrically coupled between the first and second output terminals;

the controller is adapted to control the first switching device to maximize the average value of the voltage at the intermediate switching node in a first operating mode of the switching circuit; and

the controller is adapted to continuously operate the second switching device in its conductive state in a second operating mode of the switching circuit.

27. The switching circuit of claim 26, wherein the controller is further adapted to operate the switching circuit in the second operating mode if a magnitude of a voltage of an electric power source powering the controller is greater than a first threshold value and less than or equal to a second threshold value.

28. The switching circuit of claim 26, wherein the controller is further adapted to operate the switching circuit in the second operating mode upon occurrence of an event selected from the group consisting of (1) power transferred from the input port to the output port being below a threshold value, (2) a magnitude of current through the input port being below a threshold value, (3) current flowing between the first and second output terminals exceeding a threshold value, and (4) a temperature of the switching circuit exceeding a threshold value.

29. The switching circuit of claim 1, the output port comprising a first and a second output terminal, the controller configured to control operation of the switching circuit such that current flows between the first and second output terminals in only a single direction.

30. The switching circuit of claim 1, wherein a frequency at which the first switching device switches between its conductive state and non-conductive states is loosely controlled.

31. A switching circuit for extracting power from an electric power source, comprising:

a first and a second input terminal;

a first and second output terminal for electrically coupling to a load;

a first switching device electrically coupled between the first input terminal and an intermediate switching node, the first switching device configured to switch between its conductive state and its non-conductive state;

a second switching device electrically coupled between the second input terminal and the intermediate switching node and adapted to provide a path for current between the first and second output terminals when the first switching device is in its non-conductive state; and

a controller configured to control switching of the first switching device in response to a change in an average value of a voltage across the second switching device such that an amount of electric power extracted from an electric power source electrically coupled to the first and second input terminals is at least substantially maximized.

32. A switching circuit for extracting power from an electric power source, comprising:

an input port for electrically coupling to the electric power source;

an output port for electrically coupling to a load;

a first switching device configured to switch between its conductive state and its non-conductive state to transfer power from the input port to the output port; and

a controller for controlling the first switching device to maximize an average value of a voltage across the output port.

33. The switching circuit of claim 32, wherein:

the input port comprises a first and second input terminal;

the first switching device is electrically coupled between the first input terminal and an intermediate switching node; and

the switching circuit further comprises;

a device selected from the group consisting of a diode and a second switching device electrically coupled between the second input terminal and the intermediate switching node,

an inductor electrically coupled between the intermediate switching node and the output port, and

a capacitor electrically coupled across the output port.

34. A switching circuit for extracting power from an electric power source, comprising:

an input port for electrically coupling to the electric power source;

an output port for electrically coupling to a load, the output port including a first and a second output terminal;

a first switching device configured to switch between its conductive state and its non-conductive state to transfer power from the input port to the output port;

an energy storage device; and

a controller configured to control switching of the first switching device to at least substantially maximize an amount of power extracted from the electric power source,

wherein the switching circuit is configured such that when an electric power source electrically coupled to the input port provides insufficient power to operate the controller and electric power is available at the output port;

the energy storage device is repeatedly charged from energy available via the first and second output terminals, and

the controller is at least partially powered from energy stored in the energy storage device.

35. The switching circuit of claim 34, further comprising a second switching device configured to provide a path for current between the first and second output terminals when the first switching device is in its non-conductive state, and wherein the controller is adapted to cause the second switching device to operate in its conductive state when the controller is powered from the energy storage device.

36. The switching circuit of claim 35, further comprising a diode electrically coupled in parallel with the second switching device.

37. The switching circuit of claim 36, wherein the second switching device and the diode are part of a transistor.

38. The switching circuit of claim 36, wherein the switching circuit is configured such that when the electric power source electrically coupled to the input port provides insufficient power to operate the controller and electric power is available at the output port, the second switching device and the diode alternate conduction of current between the first and second output terminals.

39. The switching circuit of claim 38, wherein the second switching device conducts current for a greater portion of time than the diode.

40. The switching circuit of claim 34, wherein:

the input port comprises a first and a second input terminal;

the switching circuit further comprises an intermediate switching node;

the first switching device is electrically coupled between the first input terminal and the intermediate switching node;

the switching circuit further comprises a second switching device electrically coupled between the second input terminal and the intermediate switching node; and

the controller is further adapted to control switching of the first switching device to maximize an average value of the voltage across the second switching device.

41. A switching circuit for extracting power from at least two electric power sources, comprising:

first and second input ports and an output port;

a first subcircuit including a first switching device adapted to switch between its conductive and non-conductive states to transfer power from the first input port to the second input port;

a second subcircuit including a second switching device configured to switch between its conductive and non-conductive states to transfer power from the second input port to the output port; and

a controller adapted to control switching of at least the first and second switching devices to at least substantially maximize transfer of power from an electric power source electrically coupled across the first input port and an electric power source electrically coupled across the second input port to a load electrically coupled to the output port.

42. The switching circuit of claim 41, wherein the first subcircuit comprises a switching circuit having a boost topology.

43. The switching circuit of claim 42, wherein:

the second switching device and a third switching device are electrically coupled in series across the second input port;

the third switching device is also electrically coupled across the output port; and

the third switching device provides a path for current through the output port when the second switching device is in its non-conductive state.

44. The switching circuit of claim 41, wherein the first subcircuit comprises a switching circuit having a buck-boost topology.

45. The switching circuit of claim 44, wherein:

the second switching device and a third switching device are electrically coupled in series across the second input port;

the third switching device is also electrically coupled across the output port; and

the third switching device provides a path for current through the output port when the second switching device is in its non-conductive state.

46. The switching circuit of claim 41, wherein the controller is adapted to switch the first and second switching devices out of phase with respect to each other.

47. The switching circuit of claim 41, wherein the controller is configured to at least substantially maximize an average value of a voltage at a switching node of the second subcircuit.

48. A system for extracting electric power from at least two electric power sources, comprising:

a buck-boost converter including an input port and an output port, the buck-boost converter operable to at least substantially maximize an amount of electric power extracted from an electric power source electrically coupled to its input port; and

a switching circuit including an input port, the switching circuit operable to at least substantially maximize an amount of electric power extracted from an electric power source electrically coupled to it input port;

wherein the output port of the buck-boost converter is electrically coupled in series with the input port of the switching circuit.

49. A switching circuit for extracting power from an electric power source, comprising:

an input port for electrically coupling to the electric power source and an output port for electrically coupling to a load;

first and second switching devices electrically coupled in series across the input port;

third and fourth switching devices electrically coupled in series across the output port;

an energy storage inductor electrically coupled in series between first and second switching nodes, the first switching node being a node where the first and second switching devices are electrically coupled, the second switching node being a node where the third and fourth switching devices are electrically coupled; and

a controller for controlling operation of the first, second, third, and fourth switching devices such that;

in a first operating mode of the switching circuit, the first and second switching devices and the energy storage inductor collectively operate as a buck converter to at least substantially maximize transfer of power from the electric power source to the load, and

in a second operating mode of the switching circuit, the third and fourth switching devices and the energy storage inductor collectively operate as a boost converter to at least substantially maximize transfer of power from the electric power source to the load.

50. The switching circuit of claim 49, the controller adapted to:

continuously operate the third switching device in its conductive state and the fourth switching device in its non-conductive state in the first operating mode of the switching circuit; and

continuously operate the first switching in its conductive state and the second switching device in its non-conductive state in the second operating mode of the switching circuit.

51. The switching circuit of claim 49, wherein:

the controller is adapted to cause the first and second switching devices to switch between their conductive and non-conductive states of a frequency of at least 200 kilohertz in the first operating mode of the switching circuit;

the controller is adapted to cause the third and fourth switching devices to switch between their conductive and non-conductive states at a frequency of at least 200 kilohertz in the second operating mode of the switching circuit; and

the switching circuit further comprises a multi-layer ceramic capacitor electrically coupled across the input port.

52. The switching circuit of claim 49, wherein the controller is adapted to at least substantially maximize an average value of a voltage across the output port in at least one of the first and second operating modes of the switching circuit.

53. The switching circuit of claim 49, where the controller is adapted to decrease a magnitude of current drawn by the switching circuit from the electric power source if a voltage across the input port drops below a threshold value.

54. A method for operating a switching circuit coupled to an electric power source such that an amount of electric power extracted from the electric power source is at least substantially maximized, comprising:

repeatedly determining an average value of a voltage at an intermediate switching node of the switching circuit;

comparing a most recent average value of the voltage at the intermediate switching node with a previous average value of the voltage at the intermediate switching node;

adjusting a duty cycle of a switching device of the switching circuit in a first direction if the most recent average value is greater than the previous average value; and

adjusting the duty cycle of the switching device in a second direction opposite of the first direction if the most recent average value is smaller than the previous average value.

55. The method of claim 54, further comprising adjusting switching of the switching device to decrease an output power of the switching circuit if an output voltage of the electric power source drops below a threshold value.

56. The method of claim 54, further comprising deactivating switching of the switching device if an output voltage of the electric power source is below a threshold value.

57. The method of claim 54, further comprising continuously operating at least one switching device of the switching circuit in its conductive state if an output voltage of the electric power source is below a threshold value.

58. The method of claim 54, further comprising decreasing a magnitude of current drawn by the switching circuit from the electric power source if an output voltage of the electric power source drops below a threshold value.

59. The method of claim 54, further comprising repeatedly determining the average value of the voltage at the intermediate switching node at a frequency that is less than a frequency at which the switching device switches between its conductive and its non-conductive states.

60. The method of claim 54, further comprising repeatedly determining the average value of the voltage at the intermediate switching node at a frequency that is less than one tenth of a frequency at which the switching device switches between its conductive and its non-conductive states.

61. A method for operating a switching circuit for interfacing an electric power source with a load, comprising the steps of:

in a first operating mode of the switching circuit, controlling switching of a first switching device of the switching circuit to at least substantially maximize an amount of power transferred from the electric power source to the load; and

in a second operating mode of the switching circuit, providing a shunt path for current flowing through the load to flow through the switching circuit.

62. The method of claim 61, further comprising transitioning from the first operating mode to the second operating mode if an output voltage of the electric power source drops below a threshold value.

63. The method of claim 61, further comprising transitioning from the first operating mode to the second operating mode if a magnitude of current flowing between the electric power source and the switching circuit drops below a threshold value.

64. The method of claim 61, further comprising transitioning from the first operating mode to the second operating mode if a magnitude of power transferred from the electric power source to the load drops below a threshold value.

65. The method of claim 61, the switching circuit including a first and second output terminal for electrically coupling to the load, the method further comprising shunting the first and second output terminals in the second operating mode.

66. The method of claim 65, the step of shunting comprising operating a second switching device electrically coupled across the first and second output terminals in its conductive state.

67. The method of claim 66, further comprising continuously operating the second switching device in its conductive state in the second operating mode.

68. The method of claim 66, further comprising extracting power from a circuit including the load to at least partially power the switching circuit in the second operating mode.

69. A method for operating a switching circuit coupled to an electric power source such that an amount of electric power extracted from the electric power source is at least substantially maximized, comprising:

repeatedly determining an operating characteristic of the switching circuit;

comparing a most recent value of the operating characteristic with a previous value of the operating characteristic;

making a maximum power point tracking adjustment to the switching circuit in a first direction if the most recent value of the operating characteristic is greater than the previous value of the operating characteristic; and

making a maximum power point tracking adjustment to the switching circuit in a second direction opposite of the first direction if the most recent value of the operating characteristic is smaller than the previous value of the operating characteristic.

70. The method of claim 69, the operating characteristic of the switching circuit being an average value of a voltage at an intermediate switching node of the switching circuit.

71. The method of claim 69, wherein:

the step of making a maximum power point tracking adjustment to the switching circuit in the first direction comprises adjusting an operating parameter of the switching circuit by a first predetermined amount; and

the step of making a maximum power point tracking adjustment to the switching circuit in the second direction comprises adjusting an operating parameter of the switching circuit by a second predetermined amount.

72. The method of claim 69, wherein:

the step of making a maximum power point tracking adjustment to the switching circuit in the first direction comprises adjusting an operating parameter of the switching circuit by a first amount that is a function of a difference between the most recent value of the operating characteristic and the previous value of the operating characteristic; and

the step of making a maximum power point tracking adjustment to the switching circuit in the second direction comprises adjusting an operating parameter of the switching circuit by a second amount that is a function of the difference between the most recent value of the operating characteristic and the previous value of the operating characteristic.

73. The method of claim 69, wherein:

the step of making a maximum power point tracking adjustment to the switching circuit in the first direction comprises adjusting an operating parameter of the switching circuit by a first amount at least partially determined from one or more historical values of the operating characteristic of the switching circuit; and

the step of making a maximum power point tracking adjustment to the switching circuit in the second direction comprises adjusting an operating parameter of the switching circuit by a second amount at least partially determined from the one or more historical values of the operating characteristic of the switching circuit.

74. The method of claim 69, further comprising performing either step of making a maximum power point tracking adjustment to the switching circuit only if a magnitude of a difference between the most recent value of the operating characteristic of the switching circuit and the previous value of the operating characteristic of the switching circuit exceeds a threshold value.

75. The method of claim 69, further comprising initially setting an operating parameter of the switching circuit to a value that previously at least substantially corresponded to a maximum power point of the electric power source.

76. The method of claim 69, further comprising decreasing a magnitude of current drawn by the switching circuit from the electric power source if an output voltage of the electric power source drops below a threshold value.

77. A method for operating a switching circuit including an input port, an output port, an energy storage device, a first switching device, and a second switching device electrically coupled across the output port, comprising:

in a first operating mode of the switching circuit, controlling switching of the first switching device between its conductive and non-conductive states to transfer power from the input port to the output port; and

in a second operating mode of the switching circuit;

charging the energy storage device with energy extracted from a circuit including the output port, and

using energy stored in the energy storage device to cause the second switching device to operate in its conductive state.

78. The method of claim 77, further comprising alternating the steps of charging and using, in the second operating mode of the switching circuit.

79. The method of claim 77, further comprising controlling switching of the first switching device to at least substantially maximize an amount of electric power extracted from an electric power source electrically coupled to the input port, in the first operating mode of the switching circuit.