LIGHT EMITTING DEVICE DRIVER CIRCUIT

• US 20080180043A1
• Filed: 03/31/2008
• Published: 07/31/2008
• 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 7,633,245 B2
• Time in Patent Office: Days
• US Class Current: 315/307
• 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 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 coupled to the light emitting device, the current sensing circuit adapted to sense driving current being supplied to the light emitting device, the current sensing circuit including an operational amplifier and a collection of resistors configured to sense a ripple in the driving current;

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 and the ripple being supplied to the one or more light emitting devices;

a pulse width modulation circuit coupled to the error amplifier circuit and adapted to modulate a pulse width of a control signal based at least in part on an output of the error amplifier circuit to compensate for the ripple sensed by the current sensing circuit, the control signal to be employed to adjust the driving current being supplied to the light emitting device; and

a buck converter coupled to the light emitting devices the buck converter adapted to switch the driving current being supplied to the light emitting device by changing amplitude of the driving current based, at least in part, on the control signal.

2. The system of claim 1, 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.

3. The system of claim 2, further comprising

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

4. The system of claim 3, wherein the controller is further adapted to receive and project a series of images as video.

5. The system of claim 1, further comprising

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

6. The system of claim 1, wherein the system comprises one of a group consisting of a projector and a projection television.