Pulse signal drive circuit

• US 7,400,310 B2
• Filed: 11/28/2005
• Issued: 07/15/2008
• Est. Priority Date: 11/28/2005
• Status: Active Grant

• Current Assignee: Dragerwerk AG & Company KGaA (FPS Vermögensverwaltung GmbH)
• Original Assignee: Draeger Medical Systems Incorporated (Dragerwerk AG)
• Inventors: LeMay, Charles R.
• Primary Examiner(s): VO, TUYET THI
• Application Number:
  US11/288,046
• Publication Number:
  US 20070120542A1
• Time in Patent Office: 960 Days
• Field of Search: 345/82, 345/90, 345/91, 345/247, 345/246, 345/224, 345/225, 345149-159, 345/291, 345/307, 315/247, 315/246, 315/224, 315/225, 315149-159
• US Class Current: 345/82
• CPC Class Codes: H05B 45/32 Pulse-control circuits
• CPC Class Codes: H05B 45/42 Antiparallel configurations
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A pulse signal drive circuit includes an energy storage device. A source of energy supplies a substantially constant flow of energy to the energy storage device. A switch circuit draws repetitive pulses of substantially constant energy from the energy storage device to generate corresponding pulse drive signals.

Claims

1. A pulse signal drive circuit, comprising:

a source of energy, said source of energy including a controllable current source;

an energy storage device, coupled to the energy source, for receiving a substantially constant flow of current from the current source, said energy storage device including a capacitor;

a switch circuit including a series connection of a load circuit and a switch, coupled to the energy storage device, for drawing repetitive pulses of substantially constant current from the energy storage device to generate corresponding pulse signals, said load circuit including a light emitting diode (LED) and said switch including a transistor having a main conductive path coupled between said LED and a source of common voltage (ground); and

a source of a bistate drive signal coupled to the transistor for conditioning the main conduction path of the transistor to not conduct in response to a first state of the bistate drive signal and to conduct in response to a second state of the bistate drive signal.

2. The circuit of claim 1 wherein:

the capacitor exhibits a voltage depending on the amount of energy stored in it; and

the load circuit draws a current directly related to the voltage across the capacitor.

3. The circuit of claim 1 wherein the energy storage device is maintained in an equilibrium condition.

4. The circuit of claim 3 wherein the average substantially constant flow of energy from the energy source to the energy storage device is substantially equal to the average energy drawn from the energy storage device in the repetitive pulses of substantially constant energy.

5. A pulse signal drive circuit, comprising:

a source of energy, said source of energy including a controllable current source;

an energy storage device, coupled to the energy source, for receiving a substantially constant flow of current from the current source, said energy storage device including a capacitor; and

a switch circuit including a series connection of a load circuit and a switch, coupled to the energy storage device, for drawing repetitive pulses of substantially constant current from the energy storage device to generate corresponding pulse signals,

the load circuit comprises a light emitting diode (LED);

the series connection comprises the series connection of a first single-pole-double-throw switch, the LED, and a second single-pole-double-throw switch coupled between the capacitor and a source of a common voltage (ground).

6. The circuit of claim 5 further comprising a source of a drive signal coupled to the first and second single-pole-double-throw switches for conditioning the LED to not conduct in response to a first state of the drive signal and conditioning the LED to conduct in response to a second state of the drive signal.

7. In an SpO₂ patient monitoring system including at least one LED for producing optical pulse signals, a pulse signal drive circuit coupled to the LED and comprising:

a controllable current source;

a capacitor, coupled to the controllable current source, for receiving a substantially constant current from the current source; and

a switch circuit, coupled to the capacitor and the LED for drawing repetitive pulses of substantially constant current from the capacitor, and providing the pulses to the LED to condition the LED to produce optical pulse signals, the switch circuit comprises the series connection of a first single-pole-double-throw switch, an LED and a second single-pole-double-throw switch.

8. The system of claim 7 wherein the switch circuit comprises the series connection of an LED and the main conduction path of a transistor.

9. The system of claim 7 further comprising a source of a bistate drive signal, coupled to the transistor, for conditioning the main conductive path of the transistor to not conduct in response to a first state of the bistate drive signal, and to conduct in response to a second state of the bistate drive signal.

10. The system of claim 7 wherein the capacitor is maintained in an equilibrium condition.

11. The system of claim 10 wherein the average current of the substantially constant current received by the capacitor from the current source is substantially equal to the average current of the repetitive pulses of substantially constant current from the switch circuit.

12. In an SpO₂ patient monitoring system including at least one LED for producing optical pulse signals, a pulse signal drive circuit coupled to the LED and comprising:

a controllable current source;

a capacitor, coupled to the controllable current source, for receiving a substantially constant current from the current source; and

a switch circuit, coupled to the capacitor and the LED for drawing repetitive pulses of substantially constant current from the capacitor, and providing the pulses to the LED to condition the LED to produce optical pulse signals,

a second LED;

a second controllable current source; and

a second capacitor, coupled to the second controllable current source, for receiving a substantially constant current from the second current source;

wherein;

the switch circuit is further coupled to the second capacitor and the second LED for drawing repetitive pulses of substantially constant current from the second capacitor, and providing the pulses to the second LED to condition the second LED to produce optical pulse signals.

13. The system of claim 12 wherein the switch circuit comprises the series connection of a first single-pole-double-throw switch, the parallel connection of the first mentioned LED and the second LED, and a second single-pole-double-throw switch.

14. The system of claim 13 wherein:

an anode of the first mentioned LED is coupled to a cathode of the second LED and the cathode of the first mentioned LED is coupled to the anode of the second LED; and

further comprising;

a source of a drive signal, coupled to the first and second single-pole-double-throw switches, for conditioning the first mentioned LED to conduct in a first operational state, conditioning the second LED to conduct in a second operational state; and

conditioning the first mentioned LED and the second LED to not conduct in a third operational state.