Reforming wet-tantalum capacitors in implantable defibrillators and other 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:
- a) 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
b) discharging, after the time, the at least one of the wet-tantalum capacitors through a non-therapeutic load, wherein discharging includes allowing the charge on at least one capacitor to dissipate through leakage current.
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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 components in these devices are aluminum electrolytic capacitors, which store and deliver one or more life-saving bursts of electric charge to a heart of a patient. This type of capacitor requires regular “reform” to preserve its charging efficiency over time. Because reform expends valuable battery life, 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 maintaining this voltage for about five minutes before discharging them.
87 Citations
24 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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a) 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 b) discharging, after the time, the at least one of the wet-tantalum capacitors through a non-therapeutic load, wherein discharging includes allowing the charge on at least one capacitor to dissipate through leakage current. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. An apparatus comprising:
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a) a lead system suitable for sensing electrical signals of a heart and for delivering electrical therapy to a heart; b) a therapy system coupled to the lead system, wherein the therapy system includes a capacitor system to store electrical energy to be delivered in measured doses through lead system, the capacitor system including at least one wet-tantalum capacitor; c) a monitoring system coupled to the lead and therapy systems, wherein the monitoring system maintains the at least one capacitor at a high voltage and periodically discharges the at least one capacitor through leakage current; and d) an implantable housing containing the therapy, capacitor, and monitor systems. - View Dependent Claims (21, 22, 23, 24)
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Specification