Claims
- 1. A pulse oximetry device that converts pulses into light flashes, comprising:
a diode for emitting the light flashes; a current sense element for sensing at least a part of a current being supplied to the diode of the oximeter; and a feedback-controlled switch for switching the diode on and off.
- 2. An oximetry device as claimed in claim 1, wherein the diode is an LED.
- 3. An oximetry device as claimed in claim 1, wherein the diode is a laser diode.
- 4. An oximetry device as claimed in claim 1, wherein the feedback-controlled switch comprises an op-amp, a control switch, and a transistor.
- 5. An oximetry device as claimed in claim 4, wherein the op-amp comprises a first input, a second input, and an output, the first input being directly connected to a reference voltage.
- 6. An oximetry device as claimed in claim 5, wherein the control switch comprises an input, connected to the output of the op-amp, and a plurality of switch outputs.
- 7. An oximetry device as claimed in claim 6, wherein the transistor comprises a control input, connected to one of the plurality of switch outputs, a current source terminal, and a supply terminal.
- 8. An oximetry device as claimed in claim 7, wherein the diode is connected to the current source terminal of the transistor.
- 9. An oximetry device as claimed in claim 8, wherein the supply terminal of the transistor is connected both to the second input of the op-amp and to a second one of the plurality of switch outputs.
- 10. An oximetry device as claimed in claim 4, wherein the transistor comprises one of a bipolar transistor, a field effect transistor, an insulated-gate semiconductor, and a semiconductor controlled rectifier.
- 11. A pulse oximeter that converts pulses into light flashes, comprising:
a plurality of diodes for emitting the light flashes; a plurality of current sense elements corresponding to the plurality of diodes, for sensing at least a part of a current being supplied to each respective diode of the oximeter; and a feedback-controlled switch for switching a selected one of the plurality of diodes on and off.
- 12. An oximeter as claimed in claim 11, wherein the plurality of diodes are LEDs.
- 13. An oximeter as claimed in claim 11, wherein the plurality of diodes are laser diodes.
- 14. An oximeter as claimed in claim 11, wherein the feedback-controlled switch comprises an op-amp, a control switch, and a plurality of transistors corresponding to the plurality of diodes.
- 15. An oximeter as claimed in claim 14, wherein the op-amp comprises a first input, a second input, and an output, the first input being directly connected to a reference voltage.
- 16. An oximeter as claimed in claim 15, wherein the control switch comprises a switch input connected to the output of the op-amp, and a plurality of switch outputs corresponding to the plurality of diodes.
- 17. An oximeter as claimed in claim 16, wherein each of the plurality of transistors comprises a control input, connected to a corresponding different one of the plurality of switch outputs, a current source terminal, and a supply terminal.
- 18. An oximeter as claimed in claim 17, wherein the each of the plurality of diodes is connected to the current source terminal of a corresponding one of the plurality of transistors.
- 19. An oximeter as claimed in claim 18, wherein the supply terminal of each of the plurality of transistors is connected both to the second input of the op-amp and to a second one of the plurality of switch outputs.
- 20. An oximeter as claimed in claim 14, wherein the plurality of transistors comprise one of bipolar transistors, field effect transistors, insulated-gate semiconductors, and semiconductor controlled rectifiers.
- 21. An oximeter as claimed in claim 1, further comprising a current-changing device for varying a drive current to the diode.
- 22. An oximeter according to claim 21, wherein the current sensing element comprises a network of individual resistors that are adapted to be selectively connected in different series and/or parallel combinations.
- 23. An oximeter according to claim 22, further comprising low ohm transistors operative to perform a connecting of ones of the individual resistors.
- 24. An oximeter according to claim 21, wherein the current sensing element comprises a variable resistor.
- 25. An oximeter as claimed in claim 11, further comprising a current-changing device for individually varying a plurality of drive currents corresponding to the plurality of diodes.
- 26. A current driving apparatus in an oximeter, comprising:
a voltage-to-current converter having a feedback loop; an unswitched reference voltage source directly connected to an input of the voltage-to-current converter; and a switch disposed in the feedback loop, whereby the unswitched reference voltage source is isolated from the switch.
- 27. A method of driving a current through a diode in a pulse oximeter that converts pulses into light flashes, comprising:
connecting a feedback-controlled device to the diode of the pulse oximeter, the diode being for emitting the light flashes, the feedback-controlled device comprising a feedback loop having a switch; switching on and off the diode by changing a switch position of the switch.
- 28. A method according to claim 27, further comprising changing a value of a current sensing resistor disposed in series with the diode, for changing a drive current to the diode.
- 29. A method according to claim 28, wherein the changing of the value of current sensing resistor is effected by selectively connecting individual resistors of a resistor network in different series/parallel combinations.
- 30. A method according to claim 27, further comprising modulating the current through the diode.
- 31. A method of using a switch for switching current through a light flash emitting diode of a pulse oximeter on or off, the method comprising:
sensing a current passing through a current path that includes the diode of the pulse oximeter; directly connecting a reference voltage to an amplifier; causing the amplifier to regulate the current passing through the current path according to the reference voltage and the sensed current; and placing the switch in a feedback loop of the amplifier.
- 32. A method of on/off controlling a current through a diode of an oximeter, comprising switching an output of a feedback amplifier, in a feedback loop of the feedback amplifier.
- 33. A method according to claim 31, further comprising directly supplying an unswitched reference voltage to the feedback amplifier in order to stabilize the current.
- 34. A method according to claim 31, further comprising modulating the current through the diode.
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is related to U.S. patent application Ser. No. ______ [SN not yet assigned] titled “Ferrite Stabilized LED Drive”, and to U.S. patent application Ser. No. ______ [SN not yet assigned] titled “Nulled Op-Amp Current Feedback”, both filed [date when filed].