ISOLATOR CIRCUIT FOR USE WITH ELECTRICAL MEDICAL EQUIPMENT

• US 3,808,502 A
• Filed: 08/07/1972
• Issued: 04/30/1974
• Est. Priority Date: 08/07/1972
• Status: Expired due to Term

• Current Assignee: Algis John Babilius
• Original Assignee: Algis John Babilius
• Inventors: Babilius, Algis John
• Primary Examiner(s): Miller, J. D.
• Assistant Examiner(s): Moose, Jr., Harry E.
• Application Number:
  US05/278,638
• Time in Patent Office: 631 Days
• Field of Search: 317/9R 321/2 128/2.1A,2.6R
• US Class Current: 361/1
• CPC Class Codes: A61B 5/301 providing electrical separation, e.g. by using isolating transformers or optocouplers
• CPC Class Codes: H04B 10/802 for isolation, e.g. using optocouplers
• CPC Class Codes: Y10S 128/908 Patient protection from electric shock

Abstract

An isolator circuit for physically and electrically insulating or isolating electrical equipment from a patient to whom the equipment is normally connected by electrodes, is disclosed. The isolator circuit is electrically interposed between the equipment and the patient by having the electrodes connected to the isolation circuit. Signals that are provided from the patient are converted from voltage signals to light signals for transmission via an optical or photo coupler to an optical receiver for subsequent reconversion to a voltage signal that is suitable for use by the electrical equipment. The isolator power supply is multi-staged and includes a transformer having a high breakdown voltage.

Claims

1. An isolator circuit for electrically isolating input terminals from output terminals, body generated signals supplied to said input terminals from a patient via connecting electrodes being transmitted froM said input terminals to said output terminals wherein a plurality of different input terminals are available to provide body generated signals, said isolator circuit comprising:

optical coupling means for transmitting an optical signal between a light transmitter and a light receiver thereof, said optical signal being light having a controlled intensity in response to control signals applied to said light transmitter;

control means operatively connected to said input terminals, for continuously applying control signals to said light transmitter for varying the intensity of said light in response to the amplitude of body generated signals applied to said input terminals, said intensity of said light being continuously representative of the amplitude of said body generated signals;

output means operatively connected to said light receiver for providing electrical output signals at said output terminals, said electrical output signals having the same waveshape as said body generated signals; and

power supply means for providing DC voltages to the components of said isolator circuit, said power supply means including;

first converter means for converting standard AC voltages to first DC voltages, second converter means for converting said first DC voltages to a chopped DC voltage signal, third converter means for providing said DC voltages to the components of said isolator circuit in response to the application of said chopped DC voltage signals to said third converter means, and a low capacitance transformer having a breakdown voltage that is at least several times the maximum voltage that is applied to said transformer, said transformer operating to apply said chopped DC voltage signals to said third converter means.

2. The isolator circuit defined by claim 1, wherein said body generated signals are voltage signals and said control signals are current signals, said control means including voltage-to-current converter means for converting voltage signals representative of said body generated signals to current signals for use as said control signals, changes in the amplitude of said current signal corresponding to changes in the amplitude of said voltage signals.

3. The isolation circuit defined by claim 1, wherein said light receiver provides current signals to said output means in response to light from said light transmitter impinging on said light receiver, said output means including means for converting the current signals provided from said light receiver to voltage signals for use as said electrical output signals, changes in the amplitude of said electrical output signals corresponding to changes in the amplitude of said current signals from said light receiver.

4. The isolator circuit defined by claim 1, further including protection means for protecting said control means against damage resulting from the application thereto of high amplitude transients.

5. The isolator circuit defined by claim 1, said control means including:

means for providing control signals to said light transmitter to have light of a selected ambient intensity emitted by said light transmitter during ambient conditions when no body generated signals are applied to said input terminals; and

means for causing said control signals to be varied to increase the intensity of said light beyond said selected ambient intensity in response to variations in the amplitude of said body generated signals.

6. The isolator circuit defined by claim 5, said control circuit further including means for limiting the amplitude of said control signals to be between preselected positive and negative threshold values.

7. The isolation circuit defined by claim 5, wherein said light receiver provides current signals to said output means in response to light from said light transmitter impinging on said light receiver, said output means including means for converting the current signals provided from said light receiver to voltage signals for use as said electrical output signals, changes in the amplitude of said electrical output signals corresponding to changes in the amplitude of said current signals from said light receiver.

8. The isolator circuit defined by claim 7, wherein said body generated signals are voltage signals and said control signals are current signals, said control means including voltage-to-current converter means for converting voltage signals representative of said body generated signals to current signals for use as said control signals, changes in the amplitude of said current signal corresponding to changes in the amplitude of said voltage signals.

9. The isolator circuit defined by claim 8, said control circuit further including means for limiting the amplitude of said control signals to be between preselected positive and negative threshold values.

10. The isolator circuit defined by claim 9, further including protection means for protecting said control means against damage resulting from the application thereto of high amplitude transients.

11. An isolator circuit for electrically isolating input terminals from output terminals, body generated signals supplied to said input terminals from a patient via connecting electrodes being transmitted from said input terminals to said output terminals wherein a plurality of different input terminals are available to provide body generated signals, said isolator circuit comprising;

optical coupling means for transmitting an optical signal between a light transmitter and a light receiver thereof, said optical signal being light having a controlled intensity in response to control signals applied to said light transmitter;

control means operatively connected to said input terminals, for continuously applying control signals to said light transmitter for varying the intensity of said light in response to the amplitude of body generated signals applied to said input terminals, said intensity of said light being continuously representative of the amplitude of said body generated signals;

output means operatively connected to said light receiver for providing electrical output signals at said output terminals, said electrical output signals having the same waveshape as said body generated signals;

switching means for controllably applying body generated signals to said control means from selected combinations of said input terminals; and

blanking means for disabling said control means for selected periods of time in response to operation of said switching means to change the combination of input terminals applying said body generated signals to said control means.

12. The isolator circuit defined by claim 11, said switching means including a plurality of switches, and means for providing a first signal when any switch thereof is closed and a second signal when none of the switches thereof are closed, said blanking means including:

first means, responsive to said second signal, for providing an enabling signal whenever a closed switch is opened;

second means, responsive to said second signal, for providing an enabling signal whenever none of said switches are closed;

third means, responsive to said first signal, for providing an enabling signal whenever a switch is closed following none of said switches being closed; and

gating means responsive to said enabling signals for providing said blanking signals.

13. The isolator circuit defined by claim 11, said control means including:

means for providing control signals to said light transmitter to have light of a selected ambient intensity emitted by said light transmitter during ambient conditions when no body generated signals are applied to said input terminals; and

means for causing said control signals to be varied to increase the intensity of said light beyond said selected ambient intensity in response to variations in the amplitude of said body generated signals.

14. The isolation circuit defined by claIm 13, wherein said light receiver provides current signals to said output means in response to light from said light transmitter impinging on said light receiver, said output means including means for converting the current signals provided from said light receiver to voltage signals for use as said electrical output signals, changes in the amplitude of said electrical output signals corresponding to changes in the amplitude of said current signals from said light receiver.

15. The isolator circuit defined by claim 14, wherein said body generated signals are voltage signals and said control signals are current signals, said control means including voltage-to-current converter means for converting voltage signals representative of said body generated signals to current signals for use as said control signals, changes in the amplitude of said current signal corresponding to changes in the amplitude of said voltage signals.

16. The isolator circuit defined by Claim 15, said switching means including a plurality of switches, and means for providing a first signal when any switch thereof is closed and a second signal when none of the switches thereof are closed, said blanking means including:

first means, responsive to said second signal, for providing an enabling signal whenever a closed switch is opened;

second means, responsive to said second signal, for providing an enabling signal whenever none of said switches are closed;

third means, responsive to said first signal, for providing an enabling signal whenever a switch is closed following none of said switches being closed; and

gating means responsive to said enabling signals for providing said blanking signals.

17. The isolator circuit defined by claim 16, further including power supply means for providing DC voltages to the components of said isolator circuit, said power supply means including:

first converter means for converting standard AC voltages to first DC voltages;

second converter means for converting said first DC voltages to a chopped DC voltage signal;

third converter means for providing said DC voltages to the components of said isolator circuit in response to the application of said chopped DC voltage signals to said third converter means; and

a low capacitance transformer having a breakdown voltage that is at least several times the maximum voltage that is applied to said transformer, said transformer operating to apply said chopped DC voltage signals to said third converter means.

18. The isolator circuit defined by claim 17, further including protection means for protecting said control means against damage resulting from the application thereto of high amplitude transients.

19. The isolator circuit defined by claim 18, said control circuit further including means for limiting the amplitude of said control signals to be between preselected positive and negative threshold values.