Method and apparatus for capacitor tolerance compensation in a cardiac stimulating device
AssigneeSiemens-Pacesetter, Inc.
InventorSergiu Silvian
Life of this patent
Estimating the term…
Abstract
A method and apparatus for determining the actual capacitance of a capacitor in a cardiac stimulating device in order to determine the potential necessary to store a desired amount of energy on the capacitor, are provided. The discharge curve of the capacitor is measured during re-forming to determine the time constant of the capacitor and the dumping resistor, and hence the actual capacitance.
Claims26
A method for determining a target potential to which a capacitor in a cardiac stimulating device must be charged to allow said cardiac stimulating device to deliver a desired energy output, wherein said capacitor has a nominal capacitance and an actual capacitance that may differ from said nominal capacitance and is in series with a resistor having a known resistance, said method comprising:
- charging the capacitor to develop a potential thereon;
- discharging the capacitor for thereby changing the potential on the capacitor as a function of time;
- measuring the potential on one of (a) the capacitor, and (b) the resistor, while said potential on the capacitor is changing;
- measuring the time interval required for said potential on said one of (a) the capacitor, and (b) the resistor, to fall from a first predetermined potential to a second predetermined potential;
- and
- calculating said target potential from said first and second predetermined potentials, said time interval, said known resistance and said desired energy output.
In a cardiac stimulating device, said cardiac stimulating device including:
- a capacitor having a nominal capacitance and an actual capacitance that may differ from said nominal capacitance,
- a power source for charging said capacitor to a target potential for delivering a desired energy output,
- a potential measuring circuit for measuring potential on said capacitor,
- a microprocessor for controlling functions of said cardiac stimulating device, and
- a resistor having a known resistance for re-forming said capacitor;
- a method for determining said target potential to which said capacitor must be charged to allow said cardiac stimulating device to deliver said desired energy output, accounting for variation between said nominal capacitance and said actual capacitance, without increasing power consumption in said cardiac stimulating device, said method comprising:
- initiating re-forming of said capacitor including:
- charging said capacitor from said power source to a first predetermined potential, and
- discharging said capacitor through said resistor;
- measuring, with said potential measuring circuit, potential on said capacitor while said capacitor is discharging through said resistor;
- measuring with said microprocessor the time interval required for said capacitor to discharge from said first predetermined potential to a second predetermined potential;
- and
- calculating with said microprocessor said target potential from said first and second predetermined potentials, said time interval, said known resistance and said desired energy output.
A cardiac stimulating device comprising:
- a capacitor having a nominal capacitance and an actual capacitance that may differ from said nominal capacitance,
- a power source coupled to said capacitor for charging said capacitor to a target potential for delivering a desired energy output,
- a resistor having a known resistance switchably coupled to said capacitor for discharging said capacitor for re-forming said capacitor;
- a potential measuring circuit coupled to said capacitor for measuring the potential on said capacitor;
- a microprocessor for controlling operation of said cardiac stimulating device;
- and wherein:
- said microprocessor initiates re-forming of said capacitor, by initiating charging of said capacitor from said power source to a first predetermined potential and discharging said capacitor through said resistor;
- and further wherein:
- said microprocessor measures the time interval required for said capacitor to discharge from said first predetermined potential to a second predetermined potential;
- and still further wherein:
- said microprocessor calculates said target potential from said first and second predetermined potentials, said time interval, said known resistance and said desire energy output.
Dependencies are inferred from the claim text.