Reforming wet-tantalum capacitors in implantable medical devices
First Claim
1. A method of maintaining one or more wet-tantalum capacitors in an implantable medical device, with each capacitor having a rated voltage or a maximum-energy voltage, the method comprising:
- maintaining at least one of the wet-tantalum capacitors at a high voltage relative its rated voltage or maximum-energy voltage for a time; and
discharging the one or more of the wet-tantalum capacitors through system leakage for a time; and
discharging the one or more of the wet-tantalum capacitors through a non-therapeutic load, after allowing the one or more wet-tantalum capacitors to discharge through system leakage.
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Accused Products
Abstract
Miniature defibrillators and cardioverters detect abnormal heart rhythms and automatically apply electrical therapy to restore normal heart function. Critical to this function, aluminum-electrolytic capacitors store and deliver life-saving bursts of electric charge to the heart. This type of capacitor requires regular “reform” to preserve its charging efficiency over time. Because reform expends valuable battery energy, manufacturers developed wet-tantalum capacitors, which are generally understood not to require reform. Yet, the present inventors discovered through extensive study that wet-tantalum capacitors exhibit progressively worse charging efficiency over time. Accordingly, to address this problem, the inventors devised unique reform techniques for wet-tantalum capacitors. One exemplary technique entails charging wet-tantalum capacitors to a voltage equal to about 90% of their rated voltage and allowing the charge to dissipate through system leakage for a period of time, before discharging through a non-therapeutic load.
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Citations
17 Claims
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1. A method of maintaining one or more wet-tantalum capacitors in an implantable medical device, with each capacitor having a rated voltage or a maximum-energy voltage, the method comprising:
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maintaining at least one of the wet-tantalum capacitors at a high voltage relative its rated voltage or maximum-energy voltage for a time; and
discharging the one or more of the wet-tantalum capacitors through system leakage for a time; and
discharging the one or more of the wet-tantalum capacitors through a non-therapeutic load, after allowing the one or more wet-tantalum capacitors to discharge through system leakage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of maintaining one or more wet-tantalum capacitors in an implantable medical device, with each capacitor having a rated voltage or a maximum-energy voltage, the method comprising:
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charging at least one of the wet-tantalum capacitors to a high voltage relative its rated voltage or maximum-energy voltage; and
discharging the one or more of the wet-tantalum capacitors through a non-therapeutic load, after determining that the one or more wet-tantalum capacitors has been charged to the high voltage. - View Dependent Claims (10, 11, 12, 13, 14)
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15. A method of maintaining one or more wet-tantalum capacitors in an implantable medical device, with each capacitor having a rated voltage, a tantalum anode, and a non-tantalum cathode, the method comprising:
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maintaining at least one of the wet-tantalum capacitors at a voltage equal to about 90% of its rated voltage for a time of about five minutes;
discharging the one or more of the wet-tantalum capacitors through system leakage for a time; and
discharging the one or more of the wet-tantalum capacitors through a non-therapeutic load, after allowing the one or more wet-tantalum capacitors to discharge through system leakage.
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16. An implantable medical device for implantation into a patient, comprising:
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one or more wet-tantalum capacitors; and
means for maintaining at least one of the wet-tantalum capacitors at a voltage equal to about 90% of its rated voltage for a time of about five minutes;
means for discharging the one or more of the wet-tantalum capacitors through system leakage for a time; and
means for discharging the one or more of the wet-tantalum capacitors through a non-therapeutic load, after allowing the one or more wet-tantalum capacitors to discharge through system leakage.
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17. An implantable heart rhythm management device comprising:
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one or more leads for sensing electrical signals of a patient or for applying electrical energy to the patient;
a monitoring circuit for monitoring heart activity of the patient through one or more of the leads; and
a therapy circuit for delivering electrical energy through one or more of the leads to a heart of the patient, wherein the therapy circuit includes a capacitor system having one or more wet-tantalum capacitors, each having a rated voltage;
means for maintaining at least one of the wet-tantalum capacitors at a high voltage relative its rated voltage for a time;
means for discharging the one or more of the wet-tantalum capacitors through system leakage for a time; and
means for discharging the one or more of the wet-tantalum capacitors through a non-therapeutic load, after allowing the one or more wet-tantalum capacitors to discharge through system leakage.
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Specification