Patent US9863982

Bi-directional current sensing circuit
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US9863982

1. A circuit for sensing current conducting in a power transistor coupled between an input power supply and a power regulator, the circuit comprising: (4) (3)

a first current loop comprising a first current sensing transistor coupled between a first terminal of the power transistor and a current sensing circuit node coupled to a current sensing circuit, the first current loop configured to sense current conducting in the power transistor during a forward current mode of the circuit;

a second current loop comprising a second current sensing transistor coupled between the current sensing circuit node and a second terminal of the power transistor, the second current loop configured to sense current conducting in the power transistor during a reverse current mode of the circuit,

wherein only one of the first current sensing loop and the second current sensing loop is active at a time based on whether the circuit is in the forward current mode or the circuit is in the reverse current mode.

2. The circuit of claim 1 further including a level shifter configured to provide complementary outputs based on the circuit mode, the level shifter having a first output coupled with a gate terminal of the first current sensing transistor to activate or deactivate the first current sensing transistor, and a second output coupled with a gate terminal of the second current sensing transistor to activate or deactivate the second current sensing transistor wherein the complementary outputs of the level shifter are configured to either turn on the first current sensing transistor and turn off the second current sensing transistor when the circuit is in forward current mode, or turn off the first current sensing transistor and turn on the second current sensing transistor when the circuit is in reverse current mode. (0)

3. The circuit of claim 1 wherein the first current sensing loop comprises the first current sensing transistor coupled with an operational amplifier, wherein the operational amplifier is configured to equalize voltage of the first terminal of the power transistor with a voltage of a corresponding terminal of the first current sensing transistor. (2) (0)

7. The circuit of claim 1 further comprising selection logic configured for selecting between sensing forward current and reverse current in the power transistor based on the mode of the circuit. (2) (0)

10. The circuit of claim 1 further comprising a buffer circuit adapted to buffer current conducting in the current sensing circuit node of the circuit and to provide a buffered voltage to the power regulator. (0)

11. A method for sensing current conducting in a power transistor coupled between an input power supply and a power regulator, the method comprising: (6) (5)

sensing current conducting in the power transistor during a forward current mode of the circuit with a first current loop comprising a first current sensing transistor coupled between a first terminal of the power transistor and a current sensing circuit node;

sensing current conducting in the power transistor during a reverse current mode of the circuit with a second current loop comprising a second current sensing transistor coupled between the current sensing circuit node and a second terminal of the power transistor,

wherein the first and second current sensing transistors form a series connection in parallel with the power transistor;

and

activating only one of the first current sensing loop and the second current sensing loop based on whether the circuit is in the forward current mode or the reverse current mode.

12. The method of claim 11 further comprising providing complementary outputs from a level shifter based on a selected mode of the circuit, the level shifter having a first output coupled with a gate terminal of the first current sensing transistor to activate or deactivate the first current sensing transistor, and a second output coupled with a gate terminal of the second current sensing transistor to activate or deactivate the second current sensing transistor and either turning on the first current sensing transistor and turning off the second current sensing transistor when the circuit is in forward current mode, or turning off the first current sensing transistor and turning on the second current sensing transistor when the circuit is in reverse current mode. (0)

13. The method of claim 11 further comprising equalizing voltage of the first terminal of the power transistor with a voltage of a corresponding terminal of the first current sensing transistor using an operational amplifier. (0)

14. The method of claim 11 further comprising equalizing voltage of the second terminal of the power transistor with a voltage of a corresponding terminal of the second current sensing transistor using an operational amplifier. (0)

15. The method of claim 11 further comprising selecting between sensing forward and reverse currents in the power transistor based on the selected mode of the circuit. (0)

16. The method of claim 11 further comprising either mirroring forward current of the power transistor during forward current mode or mirroring reverse current of the power transistor during reverse current mode. (0)

17. The method of claim 11 further comprising buffering sensed current conducting in a current sensing circuit node and providing a buffered voltage to the power regulator. (0)

18. A circuit means for sensing current conducting in a power transistor coupled between an input power supply and a power regulator, the circuit means comprising: (6) (4)

means for sensing forward current conducting in the power transistor during a forward current mode of the circuit at a first current sensing transistor coupled between a first terminal of the power transistor and a current sensing circuit node in a first current loop;

means for sensing reverse current conducting in the power transistor during a reverse current mode of the circuit at a second current sensing transistor coupled between the current sensing circuit node and a second terminal of the power transistor in a second current loop,

wherein the first and second current sensing transistors form a series connection in parallel with the power transistor; and

means for activating only one of the first current sensing loop and the second current sensing loop comprising at a time based on whether the circuit is in the forward current mode or the reverse current mode.

19. The circuit means of claim 18 further comprising (0) (2)

20. The circuit means of claim 18 further comprising a means for equalizing voltage of the first terminal of the power transistor with a voltage of a corresponding terminal of the first current sensing transistor using an operational amplifier. (0)

21. The circuit means of claim 18 further comprising a means for equalizing voltage of the second terminal of the power transistor with a voltage of a corresponding terminal of the second current sensing transistor using an operational amplifier. (0)

22. The circuit means of claim 18 further comprising a means for selecting between sensing forward current and reverse current in the power transistor based on the selected mode of the circuit. (0)

23. The circuit means of claim 18 further comprising a means for either mirroring forward current of the power transistor during forward current mode or mirroring reverse current of the power transistor during reverse current mode. (0)

24. The circuit means of claim 18 further comprising a means for buffering sensed current conducting in the current sensing circuit node and for providing a buffered voltage to the power regulator. (0)

25. A circuit for sensing current conducting in a power transistor, the circuit comprising: (2) (2)

a first current loop comprising a first current sensing transistor coupled between a first terminal of the power transistor and a first node, the first current loop configured to sense current conducting in the power transistor during a charging mode and comprising a first amplifier; and

a second current loop comprising a second current sensing transistor coupled between the first node and a second terminal of the power transistor, the second current loop configured to sense current conducting in the power transistor during a discharging mode and comprising the first amplifier.

26. The circuit of claim 25 wherein the first node is coupled to a first input of the first amplifier. (1) (0)

30. The circuit of claim 25 further comprising a second circuit configured to turn off the first current sensing transistor when the second current sensing transistor is turned on, and to turn off the second current sensing transistor when the first current sensing transistor is turned on. (0)

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Patent US9863982

Bi-directional current sensing circuit

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