Battery monitoring means and method for an implantable tissue stimulator
First Claim
1. In an implantable tissue stimulator powered by a battery having a positive terminal and a negative terminal, a battery monitoring means comprising:
- means for drawing a loading current from said battery that results in said battery output voltage having a predetermined relationship with respect to a reference voltage; and
means for generating a battery monitoring signal related to said loading current, said battery monitoring signal being related to the internal impedance of said battery.
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Accused Products
Abstract
A battery monitoring means for an implantable tissue stimulator in which a signal related to the internal impedance of an implanted battery is telemetered to an external receiving means. More specifically, the implanted battery is loaded by a varible load until current flowing through the battery lowers its output voltage until it has a predetermined relationship with respect to a reference voltage. The current flowing through the battery to achieve the predetermined relationship is directly related to the internal impedance of the battery. A voltage related to the value of this current is then telemetered to the external receiving means. In a specific embodiment, the variable load is a field effect transistor (FET) connected as a source follower. The impedance of the FET is controlled by the output of an operational amplifier having as inputs the reference voltage and a voltage related to the output voltage of the battery. The monitoring means operates in a closed-loop servo system manner until the two input voltages to the operational amplifier are equal. The other terminal of the battery is connected to a shunting resistor. Thus the voltage drop across the shunting resistor is related to the current drawn from, and the internal impedance of, the battery. This voltage is telemetered to the external receiving means.
52 Citations
20 Claims
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1. In an implantable tissue stimulator powered by a battery having a positive terminal and a negative terminal, a battery monitoring means comprising:
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means for drawing a loading current from said battery that results in said battery output voltage having a predetermined relationship with respect to a reference voltage; and means for generating a battery monitoring signal related to said loading current, said battery monitoring signal being related to the internal impedance of said battery. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. In an implantable tissue stimulator powered by a battery having positive and negative terminals, said tissue stimulator having a telemetry means for transmitting and receiving signals related to the operation of said tissue stimulator, a battery monitoring means comprising:
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a variable loading means connected to a first of said battery terminals; means for generating a reference voltage; means for controlling said variable loading means so that a voltage related to said battery output voltage has a predetermined relationship with respect to said reference voltage, said battery providing a loading current when said predetermined relationship exists; means for generating a battery monitoring signal related to said loading current, said battery monitoring signal being related to said battery internal impedance; and means for providing said battery monitoring signal to said telemetry means. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18)
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19. In an implantable tissue stimulator powered by a battery, a method for determining the internal impedance of said battery comprising the steps of:
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drawing a loading current from said battery that results in said battery output voltage having a predetermined relationship with respect to a reference voltage, said loading current being related to the internal impedance of said battery; and generating a battery monitoring signal related to said loading current. - View Dependent Claims (20)
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Specification