Light emitting device driver circuit

• US 20060193357A1
• Filed: 02/28/2005
• Published: 08/31/2006
• Est. Priority Date: 02/28/2005
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: InFocus Corporation (Lap-Shun Hui, MBA)
• Inventors: Pruett, Henry Frazier
• Granted Patent: US 7,372,883 B2
• Time in Patent Office: Days
• US Class Current: 372/38.07
• CPC Class Codes: H01S 5/042 Electrical excitation ; Circuits therefor monolithically integrated laser drive components H01S5/0261

Abstract

A driver circuit is designed employing a current sensing circuit adapted to sense driving current being supplied to one or more light emitting devices. The driver circuit additionally employs a pulse width modulation circuit adapted to modulate a pulse width of a control signal based at least in part on an output of the current sensing circuit, the control signal being employed to adjust the driving current being supplied to the one or more light emitting devices. The driver circuit additionally employs a buck converter adapted to switch the driving current being supplied to the one or more light emitting devices.

Claims

1. A driving circuit comprising:

a current sensing circuit coupled to one or more light emitting devices, the current sensing circuit adapted to sense driving current being supplied to the one or more light emitting devices;

a pulse width modulation circuit coupled to the current sensing circuit and adapted to modulate a pulse width of a control signal based at least in part on an output of the current sensing circuit, the control signal being employed to adjust the driving current being supplied to the one or more light emitting devices; and

a buck converter coupled to the one or more light emitting devices, the buck converter adapted to switch the driving current being supplied to the one or more light emitting devices.

2. The driving circuit of claim 1, wherein at least one of the one or more light emitting devices comprises a selected one of a light emitting diode and a laser diode.

3. The driving circuit of claim 1, wherein the driving circuit further comprises an error amplifier circuit coupled to the current sensing circuit, and the current sensing circuit is adapted to supply a first voltage to the error amplifier circuit, the first voltage being related to the driving current being supplied to the one or more light emitting devices.

4. The driving circuit of claim 3, wherein the error amplifier circuit is further supplied with a second voltage, and the second voltage is used at least in part to specify the amplitude of the driving current being supplied to the one or more light emitting devices.

5. The driving circuit of claim 4, wherein the second voltage is a variable voltage that is used at least in part to specify the amplitude of the driving current being supplied to the one or more light emitting devices.

6. The driving circuit of claim 1, wherein the driving current being supplied to the one or more light emitting devices is greater than or equal to approximately 1 ampere.

7. The driving circuit of claim 1, wherein the pulse width modulation circuit modulates the pulse width of the control signal to compensate for a ripple sensed in the driving current being supplied to the one or more light emitting devices, the ripple including at least approximately fifty kilohertz of oscillation.

8. The driving circuit of claim 1, wherein the pulse width modulation circuit modulates the pulse width of the control signal to compensate for a ripple sensed in the driving current being supplied to the one or more light emitting devices, the ripple being approximately between twenty kilohertz and one megahertz.

9. The driving circuit of claim 1, wherein the one or more light emitting devices are coupled to each other in series, the anode of one light emitting device being at a higher voltage potential than the anodes of the other light emitting devices coupled in series;

and

a current sensing portion of the current sensing circuit is coupled in series with the one or more light emitting devices, a node of the current sensing portion of the current sensing circuit being coupled to the anode of the first light emitting device.

10. The driving circuit of claim 1, wherein the one or more light emitting devices are monochromatic and a driving current supplied to the one or more light emitting devices is specific to the color output of the light emitting devices.

11. The driving circuit of claim 1, wherein the current sensing circuit comprises at least one current sensing resistor.

12. The driving circuit of claim 1, wherein the current sensing circuit comprises at least one operational amplifier.

13. In a projection system, a method of controlling a driving circuit comprising:

sensing driving current being supplied to one or more light emitting devices;

modulating the pulse width of a control signal to adjust the driving current based at least in part upon the sensed driving current; and

switching the driving current being supplied to the one or more light emitting devices at least in part by use of a buck converter.

14. The method of claim 13, wherein at least one of the light emitting devices comprises a selected one of a light emitting diode and a laser diode.

15. The method of claim 13, wherein the modulating of the pulse width of the control signal is at least partially performed to compensate for a ripple sensed in the driving current being supplied to the one or more light emitting devices, the ripple including at least approximately fifty kilohertz of oscillation.

16. The method of claim 13, wherein the modulating of the pulse width of the control signal is at least partially performed to compensate for a ripple sensed in the driving current being supplied to the one or more light emitting devices, the ripple being approximately between twenty kilohertz and one megahertz.

17. The method of claim 13 further comprising supplying a current to the one or more light emitting devices based on the output color of the light emitting devices, the one or more light emitting devices being monochromatic.

18. A system comprising:

an illumination source, the illumination source including a light emitting device; and

a driver circuit coupled to the light emitting device, the driver circuit including;

a current sensing circuit adapted to sense the current being supplied to the light emitting device;

a pulse width modulation circuit coupled to the current sensing circuit, the pulse width modulation circuit being adapted to modulate the pulse width of a control signal to adjust the current being supplied to the light emitting device based at least in part upon an output of the current sensing circuit; and

a buck converter coupled to the light emitting device, the buck converter adapted to switch the driving current being supplied to the light emitting device.

19. The system of claim 18, further comprising

a controller, adapted to receive an image signal and to output a light valve control signal representing an image for a frame;

and

a light valve, coupled to the controller and optically coupled to the illumination source, the light valve being adapted to modulate an incident light produced by the illumination source into image bearing light based on the light valve control signal.

20. The system of claim 19, further comprising

projection optics, optically coupled to the light valve to receive the image bearing light and to project the image.

21. The system of claim 20, wherein the controller is further adapted to receive and project a series of images as video.

22. The system of claim 18, further comprising

an image signal source, coupled to the controller, to output the image signal.

23. The system of claim 18, wherein the system comprises one of a group consisting of a projector and a projection television.