Switched capacitor defibrillation circuit

• US 20030088281A1
• Filed: 11/05/2001
• Published: 05/08/2003
• Est. Priority Date: 11/05/2001
• Status: Active Grant

• Current Assignee: Cameron Incorporated (Schlumberger NV)
• Original Assignee: Cameron Incorporated (Schlumberger NV)
• Inventors: Ostroff, Alan H., Mezack, Gary P.
• Granted Patent: US 6,778,860 B2
• Time in Patent Office: Days
• US Class Current: 607/5
• CPC Class Codes: A61N 1/3906 characterised by the form of the shockwave
• CPC Class Codes: A61N 1/3912 Output circuitry therefor, e.g. switches
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion

Abstract

A defibrillator circuit for generating a rectangular waveform across a patient from capacitively stored energy and employing a plurality of capacitors initially chargeable to a common voltage and thereafter sequentially switchable into parallel relation with one another so as to raise the voltage supplied to an H-bridge circuit from a point of decay back to said common voltage.

Claims

1. An apparatus comprising:

an H-bridge circuit adapted to be connected to a patient; and

a drive circuit connected to said H-bridge circuit and including a plurality of energy storage devices and a plurality of switches, the switches enabling each energy storage device to be charged to a common voltage and thereafter sequentially connected to supply a drive voltage to said H-bridge circuit.

2. The apparatus of claim 1 wherein each of said energy storage devices comprises a capacitor.

3. The apparatus of claim 2 wherein each capacitor is selectively couplable across a transformer secondary winding to enable charging each said capacitor to said voltage.

4. The apparatus of claim 2 wherein four capacitors are employed, each chargeable to a common voltage and each switchable into a parallel configuration with one or more of the remaining capacitors.

5. The apparatus of claim 2 wherein the time of switching of each of said plurality of capacitors is selected such that an approximation of a rectangular voltage wave is applied across said patient.

6. An apparatus of claim 5 wherein a plurality of switches are controlled so as to produce a negative going phase of a biphasic waveform after application of said approximation of a rectangular voltage.

22. The apparatus of claim 2 wherein the number of capacitors is in the range of two to seven.

25. The apparatus of claim 1 wherein said H-bridge circuit and said drive circuit form part of a subcutaneous implantable cardioverter defibrillator.

7. The apparatus comprising:

first and second switches adapted to be connected across a patient resistance and activatable when so connected to deliver a current to said patient in response to application of a voltage to said first and second switches; and

means including a plurality of capacitor means switchable into parallel relation with one another for applying an approximation of a rectangular voltage waveform to said first and second switches.

8. The apparatus of claim 7 wherein said first and second switches comprise part of an H-bridge circuit.

9. The apparatus of claim 7 wherein said waveform rises to a first voltage level, decays for a selected time interval and thereafter experiences a second rise to said first voltage level and decays for a second selected time interval.

10. The apparatus of claim 9 wherein said second rise and second decay are caused by switching of a second capacitor into parallel connection with a first of said plurality of capacitors.

11. The apparatus of claim 10 wherein said means includes a plurality of switches selectively activated to create said parallel connection.

12. The apparatus of claim 10 wherein said decay is a function of a time constant including a value which is the sum of the value of said first and second capacitors.

13. The apparatus of claim 9 wherein said means includes at least four capacitors and a plurality of switches permitting said capacitors to be selectively coupled into a plurality of parallel combinations.

14. The apparatus of claim 13 wherein said capacitors are selectively coupled so as to create a plurality of decays proportional respectively to C₁, C₁+C₂, C₁+C₂+C₃, and C₁+C₂+C₃+C₄ where C₁, C₂, C₃, and C₄ represent the respective values of said four capacitors.

15. The apparatus of claim 7 wherein each capacitor is selectively couplable across a transformer secondary winding to enable charging each said capacitor to said voltage.

16. The apparatus of claim 7 wherein four capacitors are employed, each chargeable to a common voltage and each switchable into a parallel configuration with one or more of the remaining capacitors.

17. The apparatus of claim 7 wherein first and second switches form part of an H-bridge circuit.

23. The apparatus of claim 7 wherein the number of capacitor means is in the range of two to seven.

26. The apparatus of claim 7 wherein said first and second switches and said means form part of a subcutaneous implantable cardioverter defibrillator.

18. A method of generating a drive signal for use in delivering a defibrillating signal to a patient comprising the steps of:

charging each of a plurality of capacitors to a common voltage;

applying the voltage on a first of said capacitors to create said drive signal; and

selectively connecting at least one of the remaining said plurality of capacitors in parallel with said first capacitor.

19. The method of claim 18 wherein each of said remaining capacitors is selectively coupled into a parallel configuration with one or more of the other capacitors.

20. The method of claim 18 wherein each of said capacitors is sequentially coupled into said parallel configuration.

21. The method of claim 19 wherein the timing of coupling of each successive capacitor into said parallel configuration is selected such that said drive signal approximates a rectangular pulse.

24. The method of claim 18 wherein the number of capacitors is in the range of two to seven.

27. The method of claim 18 wherein said method is performed in a subcutaneous implantable cardioverter defibrillator.