SYSTEM AND METHOD FOR PROVIDING AN ACTIVE CURRENT ASSIST WITH ANALOG BYPASS FOR A SWITCHER CIRCUIT

• US 20120105032A1
• Filed: 01/05/2012
• Published: 05/03/2012
• Est. Priority Date: 06/18/2008
• Status: Active Grant

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Huard, Jeffry Mark
• Granted Patent: US 9,083,239 B2
• Time in Patent Office: Days
• US Class Current: 323/271
• CPC Class Codes: H02M 3/1566 with means for compensating against rapid load changes, e.g. with auxiliary current source, with dual mode control or with inductance variation
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load

Abstract

A system and method are disclosed for providing an active current assist with analog bypass for a switcher circuit. An active current assist circuit is coupled to a buck regulator circuit, which includes a switcher circuit, an inductor circuit and a capacitor circuit. The active current assist circuit includes an active current analog bypass control circuit and a current source. The active current analog bypass control circuit receives and uses current limit information, voltage error information, and drop out information to determine a value of assist current that is appropriate for a current operational state of the buck regulator circuit. The active current analog bypass control circuit causes the current source to provide the appropriate value of assist current to the buck regulator circuit.

Claims

1-20. -20. (canceled)

21. A system comprising:

a switcher circuit configured to be coupled to a first end of an inductor, the switcher circuit configured to generate a current through the inductor; and

an active current assist circuit comprising;

a current source configured to be coupled to a second end of the inductor; and

an active current assist analog bypass (ACB) control circuit coupled to the switcher circuit and configured to control the current source.

22. The system of claim 21, wherein the ACB control circuit is configured to:

receive information about operation of the switcher circuit; and

in response to the received information, cause the current source to provide an assist current to the switcher circuit.

23. The system of claim 21, wherein the ACB control circuit comprises a current comparator circuit configured to receive current limit information from the switcher circuit.

24. The system of claim 21, wherein the ACB control circuit comprises a voltage error comparator circuit configured to receive voltage error information from the switcher circuit.

25. The system of claim 21, wherein the ACB control circuit comprises a pulse skip detector circuit configured to receive drop out information from the switcher circuit.

26. The system of claim 21, wherein the ACB control circuit comprises a counter configured to output a variable multi-bit count value based on information from the switcher circuit in order to control the current source.

27. The system of claim 26, wherein the ACB control circuit further comprises a combination logic and state machine configured to control the counter.

28. The system of claim 21, wherein:

the switcher circuit is configured to regulate the current through the inductor up to a current limit of the inductor; and

the current source is configured to provide additional current in a path through the active current assist circuit that is parallel to the inductor when the current through the inductor reaches the current limit.

29. The system of claim 28, wherein the active current assist circuit is also configured to operate in a bypass mode in which more current flows through the active current assist circuit than through the inductor.

30. The system of claim 21, wherein:

the switcher circuit comprises a buck regulator circuit; and

the current source comprises a pull-up digital-to-analog circuit and a pull-down digital-to-analog circuit.

31. An apparatus comprising:

an active current assist circuit configured to be coupled to a switcher circuit that is connected to a first end of an inductor, the active current assist circuit comprising;

a current source configured to be coupled to a second end of the inductor; and

an active current assist analog bypass (ACB) control circuit configured to be coupled to the switcher circuit and to control the current source.

32. The apparatus of claim 31, wherein the ACB control circuit is configured to:

receive information about operation of the switcher circuit; and

in response to the received information, cause the current source to provide an assist current to the switcher circuit.

33. The apparatus of claim 31, wherein the ACB control circuit comprises a current comparator circuit configured to receive current limit information from the switcher circuit.

34. The apparatus of claim 31, wherein the ACB control circuit comprises a voltage error comparator circuit configured to receive voltage error information from the switcher circuit.

35. The apparatus of claim 31, wherein the ACB control circuit comprises a pulse skip detector circuit configured to receive drop out information from the switcher circuit.

36. The apparatus of claim 31, wherein the ACB control circuit comprises a counter configured to output a variable multi-bit count value based on information from the switcher circuit in order to control the current source.

37. The apparatus of claim 36, wherein the ACB control circuit further comprises a combination logic and state machine configured to control the counter.

38. The apparatus of claim 31, wherein the current source is configured to provide additional current in a path through the active current assist circuit that is parallel to the inductor when the current through the inductor reaches a current limit.

39. The apparatus of claim 38, wherein the active current assist circuit is also configured to operate in a bypass mode in which more current flows through the active current assist circuit than through the inductor.

40. A method comprising:

providing a first current from a switcher circuit to an inductor, the switcher circuit coupled to a first end of the inductor;

obtaining, at an active current assist circuit, information about an operation of the switcher circuit; and

in response to the received information, providing a second current from the active current assist circuit, the active current assist circuit coupled to a second end of the inductor.