Energy source isolation and protection circuit for an electronic device

• US 8,102,154 B2
• Filed: 09/04/2008
• Issued: 01/24/2012
• 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.
• Primary Examiner(s): WILLIAMS, ARUN C
• Application Number:
  US12/204,540
• Publication Number:
  US 20100052619A1
• Time in Patent Office: 1,237 Days
• Field of Search: 320/136, 320/134, 320/149, 320/148, 320/157, 320/162
• 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. A battery isolation and protection circuit for an electronic device, the circuit comprising:

a supply voltage rail;

a reference voltage rail;

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

a rechargeable battery having a positive terminal and a negative terminal directly connected to the reference voltage rail;

a voltage comparator having a first input directly connected to the supply voltage rail, a second input directly connected 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 a gate node directly connected to the output of the voltage comparator, a source node directly connected to the reference voltage rail, and a drain node;

a pull-down resistor directly connected between the gate node of the NMOS transistor and the source node of the NMOS transistor, and directly connected between the output of the voltage comparator and the reference voltage rail;

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

a pull-up resistor directly connected between the gate node of the PMOS transistor and the source node of the PMOS transistor, and directly connected between the drain node of the NMOS transistor and the positive terminal of the rechargeable battery;

wherein the relatively high voltage at the output of the voltage comparator activates the NMOS transistor to place the drain node of the NMOS transistor and the gate node of the PMOS transistor at ground potential, and to activate the PMOS transistor to connect the rechargeable battery between the supply voltage rail and the reference voltage rail; and

wherein the relatively low voltage at the output of the voltage comparator deactivates the NMOS transistor to establish an open circuit condition at the drain node of the NMOS transistor, and to deactivate the PMOS transistor to electrically isolate the rechargeable battery from the electrical load.

2. The circuit of claim 1, wherein the rechargeable battery is a rechargeable lithium ion battery.

3. The circuit of claim 1, wherein the rechargeable battery is a rechargeable lithium polymer battery.

4. The circuit of claim 1, 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.

5. The circuit of claim 4, 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.

6. The circuit of claim 5, 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.

7. The circuit of claim 6, wherein the electronic device remains in the detached mode until an external stimulus initiates switching on of the PMOS transistor.

8. The circuit of claim 7, wherein the external stimulus is associated with the coupling of an external charger between the supply voltage rail and the reference voltage rail.