DCR inductor current-sensing in four-switch buck-boost converters

1. An inductor current-sensing circuit for measuring a current in a primary inductor of a four-switch buck boost converter with an inductance and an equivalent DC resistance, the four-switch buck boost converter receiving an input voltage and providing an output voltage, the inductor current-sensing circuit comprising:

a first RC network coupled between a first terminal of the primary inductor and a virtual ground reference;

a second RC network coupled between a second terminal of the primary inductor and the virtual ground reference, wherein the first RC network and the second RC network each have a time constant substantially equal to the ratio between the inductance and the DC resistance; and

a decoupling capacitor connecting the virtual ground reference to a system ground reference.

2. The inductor current-sensing circuit of claim 1 , further comprising a sensing capacitor connected between the first RC network and the second RC network.

3. The inductor current-sensing circuit of claim 2 , wherein the sensing capacitor has a greater capacitance than an effective capacitance of each of the first and the second RC networks.

4. An inductor current-sensing circuit for measuring a current in a primary inductor of a four-switch buck boost converter with an inductance and an equivalent DC resistance, the four-switch buck boost converter receiving an input voltage and providing an output voltage, the inductor current-sensing circuit comprising:

a first RC network coupled between a first terminal of the primary inductor and a virtual ground reference; and

a second RC network coupled between a second terminal of the primary inductor and the virtual ground reference, wherein the first RC network and the second RC network each have a time constant substantially equal to the ratio between the inductance and the DC resistance, and wherein the virtual ground reference refers to the output voltage when the four-switch buck boost converter operates in a buck mode.

5. The inductor current-sensing circuit of claim 4 , further comprising a sensing capacitor connected between the first RC network and the second RC network.

6. The inductor current-sensing circuit of claim 5 , wherein the sensing capacitor has a greater capacitance than an effective capacitance of each of the first and the second RC networks.

7. An inductor current-sensing circuit for measuring a current in a primary inductor of a four-switch buck boost converter with an inductance and an equivalent DC resistance, the four-switch buck boost converter receiving an input voltage and providing an output voltage, the inductor current-sensing circuit comprising:

a first RC network coupled between a first terminal of the primary inductor and a virtual ground reference; and

a second RC network coupled between a second terminal of the primary inductor and the virtual ground reference, wherein the first RC network and the second RC network each have a time constant substantially equal to the ratio between the inductance and the DC resistance, and wherein the virtual ground reference refers to the input voltage when the four-switch buck boost converter operates in a boost mode.

8. The inductor current-sensing circuit of claim 7 , further comprising a sensing capacitor connected between the first RC network and the second RC network.

9. The inductor current-sensing circuit of claim 8 , wherein the sensing capacitor has a greater capacitance than an effective capacitance of each of the first and the second RC networks.

10. An inductor current-sensing circuit for measuring a current in a primary inductor of a four-switch buck boost converter with an inductance and an equivalent DC resistance, the four-switch buck boost converter receiving an input voltage and providing an output voltage, the inductor current-sensing circuit comprising:

a first RC network coupled between a first terminal of the primary inductor and a virtual ground reference; and

a second RC network coupled between a second terminal of the primary inductor and the virtual ground reference, wherein the first RC network and the second RC network each have a time constant substantially equal to the ratio between the inductance and the DC resistance, and wherein the virtual ground reference refers to an average of a voltage across the first terminal of the inductor and the second terminal of the inductor, when the four-switch buck boost converter operates in a buck-boost mode.

11. The inductor current-sensing circuit of claim 10 , further comprising a sensing capacitor connected between the first RC network and the second RC network.

12. The inductor current-sensing circuit of claim 11 , wherein the sensing capacitor has a greater capacitance than an effective capacitance of each of the first and the second RC networks.

13. A method for measuring a current in a primary inductor of a four-switch buck boost converter with an inductance and an equivalent DC resistance, the four-switch buck boost converter receiving an input voltage and providing an output voltage, the method comprising:

connecting a first RC network between a first terminal of the primary inductor and a virtual ground reference;

connecting a second RC network coupled between a second terminal of the primary inductor and the virtual ground reference;

connecting a decoupling capacitor between the virtual ground reference and a system ground reference; and

measuring a voltage between a node in the first RC network and a node in the second RC network, wherein the first RC network and the second RC network each have a time constant substantially equal to the ratio between the inductance and the DC resistance.

14. The method of claim 13 , wherein the node in the first RC network and the node in the second RC network each correspond to a terminal of a sensing capacitor in each RC network.

15. The method of claim 13 , further comprising connecting a sensing capacitor between the first RC network and the second RC network.

16. The method of claim 15 , wherein the sensing capacitor has a greater capacitance than an effective capacitance of each of the first and the second RC networks.

17. A method for measuring a current in a primary inductor of a four-switch buck boost converter with an inductance and an equivalent DC resistance, the four-switch buck boost converter receiving an input voltage and providing an output voltage, the method comprising:

connecting a first RC network between a first terminal of the primary inductor and a virtual ground reference;

connecting a second RC network coupled between a second terminal of the primary inductor and the virtual ground reference; and

measuring a voltage between a node in the first RC network and a node in the second RC network, wherein the first RC network and the second RC network each have a time constant substantially equal to the ratio between the inductance and the DC resistance and wherein the virtual ground reference refers to the output voltage when the four-switch buck boost converter operates in a buck mode.

18. The method of claim 17 , wherein the node in the first RC network and the node in the second RC network each correspond to a terminal of a sensing capacitor in each RC network.

19. The method of claim 17 , further comprising connecting a sensing capacitor between the first RC network and the second RC network.

20. The method of claim 19 , wherein the sensing capacitor has a greater capacitance than an effective capacitance of each of the first and the second RC networks.

21. A method for measuring a current in a primary inductor of a four-switch buck boost converter with an inductance and an equivalent DC resistance, the four-switch buck boost converter receiving an input voltage and providing an output voltage, the method comprising:

connecting a first RC network between a first terminal of the primary inductor and a virtual ground reference;

connecting a second RC network coupled between a second terminal of the primary inductor and the virtual ground reference; and

measuring a voltage between a node in the first RC network and a node in the second RC network, wherein the first RC network and the second RC network each have a time constant substantially equal to the ratio between the inductance and the DC resistance and wherein the virtual ground reference refers to the input voltage when the four-switch buck boost converter operates in a boost mode.

22. The method of claim 21 , wherein the node in the first RC network and the node in the second RC network each correspond to a terminal of a sensing capacitor in each RC network.

23. The method of claim 21 , further comprising connecting a sensing capacitor between the first RC network and the second RC network.

24. The method of claim 23 , wherein the sensing capacitor has a greater capacitance than an effective capacitance of each of the first and the second RC networks.

25. A method for measuring a current in a primary inductor of a four-switch buck boost converter with an inductance and an equivalent DC resistance, the four-switch buck boost converter receiving an input voltage and providing an output voltage, the method comprising:

connecting a first RC network between a first terminal of the primary inductor and a virtual ground reference;

connecting a second RC network coupled between a second terminal of the primary inductor and the virtual ground reference; and

measuring a voltage between a node in the first RC network and a node in the second RC network, wherein the first RC network and the second RC network each have a time constant substantially equal to the ratio between the inductance and the DC resistance and wherein the virtual ground reference refers to an average of a voltage across the first terminal of the inductor and the second terminal of the inductor, when the four-switch buck boost converter operates in a buck-boost mode.

26. The method of claim 25 , wherein the node in the first RC network and the node in the second RC network each correspond to a terminal of a sensing capacitor in each RC network.

27. The method of claim 25 , further comprising connecting a sensing capacitor between the first RC network and the second RC network.

28. The method of claim 27 , wherein the sensing capacitor has a greater capacitance than an effective capacitance of each of the first and the second RC networks.