ENERGY SOURCE ISOLATION AND PROTECTION CIRCUIT FOR AN ELECTRONIC DEVICE

• US 20100052619A1
• Filed: 09/04/2008
• Published: 03/04/2010
• Est. Priority Date: 09/04/2008
• Status: Active Grant

• Current Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Inventors: Bishop, Dennis P., Spurlin, Jon M.
• Granted Patent: US 8,102,154 B2
• Time in Patent Office: Days
• US Class Current: 320/136
• CPC Class Codes: H02J 7/00306 Overdischarge protection
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence

Abstract

An energy source isolation and protection circuit is provided for an electronic device, such as a patient-worn or patient-carried medical device. The isolation and protection circuit includes a supply voltage rail, a reference voltage rail, an electrical load coupled across the supply voltage rail and the reference voltage rail, and an energy source for supplying a voltage to the electrical load via the supply voltage rail and the reference voltage rail. The isolation and protection circuit also includes a voltage-controlled switch architecture that is configured to detach and electrically isolate the energy source from the electrical load (and from itself) in response to the voltage of the energy source falling below a threshold voltage. The voltage-controlled switch architecture is also designed to maintain the energy source in the detached and electrically isolated state in the absence of operating voltage provided by the energy source to the voltage-controlled switch architecture.

Claims

1. An energy source isolation and protection circuit for an electronic device, the circuit comprising:

a supply voltage rail;

a reference voltage rail;

an energy source having a positive terminal, a negative terminal, and an energy source voltage defined between the positive terminal and the negative terminal;

an electrically controlled switch coupled between the positive terminal and the supply voltage rail; and

a control circuit coupled to the supply voltage rail, the reference voltage rail, and the electrically controlled switch;

wherein

the energy source voltage serves as an operating voltage for the control circuit; and

in response to the energy source voltage dropping below a threshold voltage, the control circuit opens the electrically controlled switch to isolate the energy source, and to remove the energy source voltage from the control circuit.

2. The circuit of claim 1, further comprising an electrical load between the supply voltage rail and the reference voltage rail, the energy source being configured to drive the electrical load.

3. The circuit of claim 1, wherein:

the electrically controlled switch is a PMOS transistor having its gate node coupled to the control circuit, its drain node coupled to the supply voltage rail, and its source node coupled to the positive terminal of the energy source; and

the control circuit is configured to regulate voltage at the gate node of the PMOS transistor to control the electrically controlled switch.

4. The circuit of claim 3, wherein the control circuit comprises:

a voltage monitor element having a first input coupled to the supply voltage rail, a second input coupled to the reference voltage rail, and an output; and

an NMOS transistor having its gate node coupled to the output, its drain node coupled to the gate node of the PMOS transistor, and its source node coupled to the reference voltage rail;

wherein

the control circuit is configured to regulate voltage at the gate node of the NMOS transistor.

5. The circuit of claim 1, wherein the energy source comprises a battery.

6. The circuit of claim 5, wherein the battery is a rechargeable lithium ion battery.

7. The circuit of claim 1, wherein the energy source comprises a capacitor.

8. The circuit of claim 1, wherein the control circuit is configured to maintain the electrically controlled switch in an open state until an external voltage supply applies a voltage higher than the threshold voltage across the supply voltage rail and the reference voltage rail.

9. The circuit of claim 8, wherein the control circuit is configured to close the electrically controlled switch when the external voltage supply applies the voltage.

10. A battery isolation and protection circuit for an electronic device having a supply voltage rail, a reference voltage rail, a load coupled between the supply voltage rail and the reference voltage rail, and a rechargeable battery having a positive terminal and a negative terminal, the circuit comprising:

a voltage comparator having a first input coupled to the supply voltage rail, a second input coupled to the reference voltage rail, and an output, the voltage comparator being configured to generate a relatively high voltage at the output when a voltage across the first input and the second input is greater than a threshold voltage, and to otherwise generate a relatively low voltage at the output;

an NMOS transistor having its gate node coupled to the output and its source node coupled to the reference voltage rail;

a pull-down resistor coupled between the output and the reference voltage rail;

a PMOS transistor having its gate node coupled to the drain node of the NMOS transistor, its drain node coupled to the supply voltage rail, and its source node coupled to the positive terminal of the rechargeable battery; and

a pull-up resistor coupled between the drain node of the NMOS transistor and the positive terminal of the rechargeable battery.

11. The circuit of claim 10, wherein the rechargeable battery is a rechargeable lithium ion battery.

12. The circuit of claim 10, wherein the rechargeable battery is a rechargeable lithium polymer battery.

13. The circuit of claim 10, wherein the electronic device has a normal operating mode during which a voltage across the positive terminal and the negative terminal of the rechargeable battery is greater than the threshold voltage, the voltage comparator generates the relatively high voltage at the output, the NMOS transistor is switched on, and the PMOS transistor is switched on.

14. The circuit of claim 13, wherein the electronic device has a detached mode during which the NMOS transistor is switched off, the PMOS transistor is switched off, and the rechargeable battery is electrically isolated.

15. The circuit of claim 14, wherein the electronic device transitions from the normal operating mode to the detached mode in response to the voltage across the first input and the second input of the voltage comparator falling below the threshold voltage.

16. The circuit of claim 15, wherein the electronic device remains in the detached mode until an external stimulus initiates switching on of the PMOS transistor.

17. The circuit of claim 16, wherein the external stimulus is associated with the coupling of an external charger between the supply voltage rail and the reference voltage rail.

18. In an electronic device comprising a supply voltage rail, a reference voltage rail, a load between the supply voltage rail and the reference voltage rail, an energy source having a positive terminal and a negative terminal, and a transistor-based switch coupled between the supply voltage rail and the positive terminal of the energy source, a method for isolating the energy source for undercharge conditions, the method comprising:

monitoring a load voltage defined between the supply voltage rail and the reference voltage rail, the load voltage being supplied by the energy source when the transistor-based switch is closed;

detecting when the load voltage falls below a threshold voltage;

in response to the detecting step, opening the transistor-based switch to electrically isolate the energy source from the load; and

maintaining the transistor-based switch in its open state until an external stimulus causes the transistor-based switch to close.

19. The method of claim 18, further comprising:

sensing an externally applied voltage across the supply voltage rail and the reference voltage rail, the externally applied voltage being greater than the threshold voltage; and

in response to the sensing step, closing the transistor-based switch to couple the energy source between the load, and to couple the energy source between the supply voltage rail and the reference voltage rail.

20. The method of claim 19, further comprising charging the energy source with the externally applied voltage.

21. An energy source isolation and protection circuit for an electronic device, the circuit comprising:

a supply voltage rail;

a reference voltage rail;

an electrical load coupled across the supply voltage rail and the reference voltage rail;

an energy source for supplying a voltage to the electrical load via the supply voltage rail and the reference voltage rail; and

a voltage-controlled switch architecture configured to detach and electrically isolate the energy source from the electrical load, and from itself, in response to the voltage of the energy source falling below a threshold voltage, and configured to maintain the energy source in such a detached and electrically isolated state in the absence of operating voltage provided by the energy source to the voltage-controlled switch architecture.

22. The circuit of claim 21, the voltage-controlled switch architecture being configured to maintain the energy source in the detached and electrically isolated state until the voltage-controlled switch architecture is reset by an external stimulus.

23. The circuit of claim 22, wherein the external stimulus comprises an external charger coupled between the supply voltage rail and the reference voltage rail, the external charger being configured to apply a charging voltage across the supply voltage rail and the reference voltage rail, the charging voltage being greater than the threshold voltage.

24. The circuit of claim 23, the external charger being configured to apply the charging voltage to the voltage-controlled switch architecture for use as operating voltage.

25. An electronic device comprising:

a supply voltage rail;

a reference voltage rail;

an electrical load between the supply voltage rail and the reference voltage rail;

an energy source for supplying a voltage to the electrical load via the supply voltage rail and the reference voltage rail;

means for detecting when the voltage supplied by the energy source falls below a threshold voltage;

means for electrically isolating the energy source from the electrical load, the means for electrically isolating being responsive to detection of the voltage falling below the threshold voltage; and

means for preserving the energy source in its electrically isolated state until an externally applied voltage that exceeds the threshold voltage is established between the supply voltage rail and the reference voltage rail.

26. The electronic device of claim 25, wherein the means for detecting comprises a voltage comparator coupled to the supply voltage rail and the reference voltage rail.

27. The electronic device of claim 25, wherein the means for electrically isolating comprises a voltage-controlled switch architecture coupled to, and controlled by, the means for detecting.