Battery Protection and Zero-Volt Battery Recovery System for an Implantable Medical Device

• US 20070129768A1
• Filed: 10/19/2006
• Published: 06/07/2007
• Est. Priority Date: 12/07/2005
• Status: Active Grant

• Current Assignee: Boston Scientific Neuromodulation Corporation (Boston Scientific Corporation)
• Original Assignee: Advanced Bionics Corporation (Sonova Holding AG)
• Inventors: He, Yuping, Peterson, David
• Granted Patent: US 7,962,222 B2
• Time in Patent Office: Days
• US Class Current: 607/34
• CPC Class Codes: A61N 1/37 Monitoring; Protecting
• CPC Class Codes: A61N 1/378 Electrical supply
• CPC Class Codes: A61N 1/3787 from an external energy source
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H02J 2310/23 The load being a medical device, a medical implant, or a life supporting device
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• CPC Class Codes: H02J 7/0071 with a programmable schedule
• CPC Class Codes: H02J 7/00711 with introduction of pulses during the charging process
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

Circuitry useable to protect and reliably charge a rechargeable battery, even from a zero-volt state, is disclosed, and is particularly useful when employed in an implantable medical device. The circuit includes two charging paths, a first path for trickle charging the battery at a relatively low current when the battery voltage is below a threshold, and a second path for charging the battery at relatively higher currents that the battery voltage is above a certain threshold. A passive diode is used in the first trickle-charging path which allows trickle charging even when the battery voltage is too low for reliable gating, while a gateable switch (preferably a PMOS transistor) is used in the second higher-current charging path when the voltage is higher and the switch can therefore be gated more reliably. A second diode between the two paths ensures no leakage to the substrate through the gateable switch during trickle charging. The load couples to the battery through the switch, and preferably through a second switch specifically used for decoupling the load.

Claims

1. A protection and recovery circuit for an implantable medical device, comprising:

a rechargeable battery;

a charge controller for charging the rechargeable battery;

a first charging path between the charge controller and a terminal of the battery for charging the battery through at least one diode, wherein the first charging path is active to charge the battery from zero volts when a voltage of the battery is below a threshold; and

a second charging path between the charge controller and the terminal of the battery for charging the battery through a first switch, wherein the second charging path is active to charge the battery when a voltage of the battery is above the threshold.

2. The circuit of claim 1, wherein the first switch is off to deactivate the second charging path.

3. The circuit of claim 1, wherein a load is coupled to second charging path such that the first switch is active to couple the battery to the load.

4. The circuit of claim 3, further comprising a second switch between the first switch and the load for decoupling the load.

5. The circuit of claim 1, further comprising at least one diode between the first charging path and the second charging path.

6. The circuit of claim 1, wherein the first switch comprises a PMOS transistor.

7. The circuit of claim 6, wherein a well of the PMOS transistor is biased to a higher of a source or a drain of the PMOS transistor.

8. The circuit of claim 6, wherein a well of the PMOS transistor is biased to the battery voltage.

9. The circuit of claim 6, wherein a well of the PMOS transistor is biased to a voltage output by the charge controller on the first charging path.

10. A protection and recovery circuit for an implantable medical device, comprising:

a rechargeable battery with a terminal;

a charge controller for charging the rechargeable battery, wherein the charge controller has a first output and a second output;

a first charging path between the first output of the charge controller and the battery terminal, wherein the first charging path comprises at least one first diode;

a second charging path between the second output of the charge controller and the battery terminal, wherein the second charging path comprises a gateable first switch; and

at least one second diode coupled between the first output and the second output.

11. The circuit of claim 10, wherein the first switch is off to deactivate the second charging path.

12. The circuit of claim 10, further comprising a load coupled to the second output through a second switch.

13. The circuit of claim 10, wherein the first switch comprises a PMOS transistor.

14. The circuit of claim 13, wherein the well of the PMOS transistor is biased to a higher of a source or a drain of the PMOS transistor.

15. The circuit of claim 13, wherein the well of the PMOS transistor is biased to the battery voltage.

16. The circuit of claim 13, wherein a well of the PMOS transistor is biased to a voltage on the first output.

17. A method for recharging a battery in an implantable medical device, comprising:

producing a relatively low current to charge a terminal of the battery through a first path when the battery voltage is greater than or equal to zero and less than or equal to a threshold; and

producing a relatively high current to charge the terminal of the battery through a second path when the battery voltage is greater than the threshold.

18. The method of claim 17, wherein the second path is opened by a switch when the battery terminal is being charged through the first path.

19. The method of claim 17, wherein the first path comprises only a passive component, and wherein the second path comprises an active gateable component.

20. The method of claim 19, wherein the active gateable component comprises a PMOS transistor whose well is biased to ensure no current leakage through the well.

21. The method of claim 19, wherein the active gateable component is deactivated when excessive discharge is detected.

22. The method of claim 17, wherein the battery is a lithium-ion battery or a lithium-ion polymer battery.