FERRITE STABILIZED LED DRIVE

• US 20040030230A1
• Filed: 08/08/2002
• Published: 02/12/2004
• Est. Priority Date: 08/08/2002
• Status: Active Grant

• Current Assignee: Datex-Ohmeda Incorporated (General Electric Company)
• Original Assignee: Datex-Ohmeda Incorporated (General Electric Company)
• Inventors: Norris, Mark A.
• Granted Patent: US 6,707,257 B2
• Time in Patent Office: Days
• US Class Current: 600/323
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor

Abstract

An oximeter diode-driving device has a diode, a transistor operative to controllably connect current to the diode, a current sensing resistor that senses at least part of the current, a feedback amplifier operative to control the connecting of current by the transistor according to the current sensed by the current sensing resistor, and an inductor disposed in series with the current sensing resistor. A method of driving a current through the diode of an oximeter includes driving a current through the diode by connecting the current to the diode, controlling the connecting using a feedback type amplifier, the feedback type amplifier having a current source that uses a current-limiting resistor, and adding phase lead to a current passing through the current-limiting resistor.

Claims

1. A method of stabilizing the driving of a current through a diode of an oximeter, comprising:

connecting a feedback-controlled device to the diode, the feedback-controlled device comprising a feedback loop;

sensing a current being input to the feedback loop; and

adding phase lead to the sensed current with a ferrite, the ferrite being disposed in series with the sensed current.

2. A method of stabilizing the driving of a current through a diode of an oximeter, comprising:

sensing at least part of the current through the diode, using a current sense element;

controlling a connecting of the current through the diode, the controlling being based on current sensed by the current sense element; and

stabilizing the controlling with a ferrite, the ferrite being disposed in series with the current sense element, an inductance value of the ferrite being set to counteract a phase lag imposed on apparatus performing the controlling.

3. A method of stabilizing the driving a current through a diode of an oximeter as claimed in claim 2, further comprising damping the current sensed by the current sense element.

4. A method of stabilizing the driving a current through a diode of an oximeter as claimed in claim 3, wherein the damping comprises adding phase lead to the current sensed by the current sense element.

5. A method of driving a current through a diode of an oximeter, comprising:

sensing a current of a signal being input to a feedback type amplifier;

adding phase lead to the signal being input to the feedback type amplifier; and

driving a diode with at least part of the signal having added phase lead.

6. A method according to claim 5, wherein the feedback type amplifier comprises a current source having a current-limiting element.

7. A method of driving a current through a diode of an oximeter, comprising:

driving a current through the diode by connecting the current to the diode;

controlling the connecting using a feedback type amplifier, the feedback type amplifier having a current source that uses a current-limiting element; and

adding phase lead to a current passing through the current-limiting element.

8. A method of driving a current through a diode of an oximeter as claimed in claim 7, further comprising damping the current passing through the current-limiting element.

9. A method of driving a current through a diode of an oximeter as claimed in claim 7, further comprising isolating a feedback of the feedback type amplifier when the current to the diode is in an off state.

10. A method of driving a current through a diode of an oximeter as claimed in claim 7, wherein the connecting is performed by a transistor.

11. An oximeter diode-driving device, comprising:

a diode;

a transistor operative to controllably connect current to the diode;

a current sensing element that senses at least part of the current;

a feedback amplifier operative to control the connecting of current by the transistor according to the current sensed by the current sensing element; and

an inductor disposed in series with the current sensing element.

12. An oximeter diode-driving device according to claim 11, further comprising a cable connecting the diode to the transistor, wherein an inductance value of the inductor is set to counteract a phase lag caused by at least one of reactance of the cable and capacitance across the transistor.

13. An oximeter diode-driving device according to claim 12, wherein an inductance value of the inductor is set to counteract a phase lag caused by the combined sluggishness of the transistor, feedback amplifier, and cable.

14. An oximeter diode-driving device according to claim 11, further comprising:

a feedback capacitor disposed between the transistor and an inverting input of the feedback amplifier; and

a feedback element disposed in parallel with the feedback capacitor.

15. An oximeter diode-driving device according to claim 14, wherein a capacitance value of the feedback capacitor and a resistance value of the feedback element are set to define an on/off time constant for the feedback amplifier.

16. An oximeter diode-driving device according to claim 15, wherein the capacitance value of the feedback capacitor is set to counteract a phase lag caused by an input capacitance of the feedback amplifier.

17. An oximeter diode-driving device according to claim 11, further comprising a damping element disposed in parallel with the inductor.

18. An oximeter diode-driving device according to claim 17, wherein a resistance value of the damping element is set based on lowering a Q of the inductor by a predetermined amount.

19. An oximeter diode-driving device according to claim 11, wherein the diode is a laser diode.

20. An oximeter diode-driving device according to claim 11, wherein the diode is a light-emitting diode.

21. An oximeter diode-driving device according to claim 11, wherein the inductor is a ferrite bead.