Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
1999-02-26
2001-06-05
Layno, Carl H. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C607S007000
Reexamination Certificate
active
06243604
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to the charging of capacitors used with defibrillators, and in particular external defibrillators.
2. Description of the Related Art
Cardiotherapeutic defibrillators, once used only by trained medical personnel, are now being made available for use by the general population, including individuals having little or no training. The defibrillators contemplated for general use are of the automatic external type and include on-board real time diagnostic capability to intervene or otherwise control the defibrillator therapy being administered. In general, the defibrillators deliver a relatively high voltage, low energy pulse or series of pulses to a patient suffering cardiac arrhythmias, such as ventricular fibrillation. The power supply relied upon to deliver the defibrillation therapy typically comprises one or more batteries carried on board the defibrillator unit or an electrical power utility supplying mains power to a building, for example.
Because of the nature of the electrical therapy required, it is not possible in a practical device to supply the therapeutic energy upon instantaneous demand, by drawing from the power source. Instead, energy from the power source must be accumulated over a certain period of time in one or more defibrillator capacitors which are later discharged to deliver the desired defibrillation therapy. It is particularly critical that the defibrillation therapy be delivered as quickly as possible, given the nature of the medical threat encountered. Accordingly, rapid charging of the defibrillator storage capacitor is required and advances in reducing charge time are still being sought.
Due to the nature of the use to which the defibrillation equipment is put, certain components employed must be carefully constructed to close performance tolerances which are expected to be closely maintained throughout the life of the component. It is important that such components are not unexpectedly stressed during unusual operating conditions, as when main power supply voltage unexpectedly drops. Also, it would be advantageous if a closer control could be exercised over the stress to which the electrical components are put.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a charging circuit for defibrillator capacitors.
It is another object of the present invention to provide a charging circuit which employs computer or other electronic control of the circuits operation, and in particular which allows direct control of peak current in the charging circuit.
A further object of the present invention is to provide a charging circuit for defibrillator capacitors in which a larger number of defibrillator therapy events can be generated despite a greater variation in source power conditions.
These and other objects of the present invention are provided in Apparatus for charging defibrillator capacitors, comprising:
a transformer having a primary winding with primary connection means for connection to a power supply, to draw current therefrom and a secondary winding with secondary connection means for connection to said defibrillator capacitors to supply charging power thereto, said pulse transformer having a magnetic field which rises and collapses while charging said defibrillator capacitors;
field monitoring means for detecting the collapse of magnetic field of said transformer and for sending a trigger signal in response thereto;
transformer control means coupled to said transformer primary winding to control current flow therethrough in response to a control signal;
a downstream pulse generator having an output coupled to said transformer control means to provide the control signal therefor, said downstream pulse generator also having an input for receiving a driving signal and a reset port for receiving a reset signal to reset said first pulse generator, said downstream pulse generator producing an output signal pulse of pulse width determined in response to said driving signal and resettable in response to the reset signal received at said reset port;
a comparator having two inputs and an output which is coupled to said downstream pulse generator reset port;
a reference signal means coupled to one of said comparator inputs;
primary signal means coupled to the other of said comparator inputs, and producing a primary sensor signal in response to current flow through the transformer primary winding;
a multivibrator delivering a series of pulses, comprising said driving signal, to an output coupled to said downstream pulse generator input, said multivibrator further having a reset port for receiving a multivibrator reset signal so as to reset the series of pulses in response thereto;
an upstream pulse generator having an output coupled to said multivibrator reset port, an input for receiving an upstream input signal and an upstream pulse generator reset port for receiving a reset signal to reset said upstream pulse generator, said upstream pulse generator producing the multivibrator reset signal, comprising a series of reset pulses, in response to said upstream input signal;
said upstream pulse generator input coupled to said field monitoring means for receiving the trigger signal therefrom and for resetting the series of reset pulses in response thereto, thereby synchronizing the downstream pulse generator and hence said transformer control means to said collapse of magnetic field of said transformer.
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Fitch Even Tabin & Flannery
Layno Carl H.
Medical Research Laboratories, Inc.
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