Granted Patent B2

US 7,170,335 · App. 10/795,689 · Granted Jan 30, 2007

Abstract

Claims (35)

1. A driver circuit for driving a light source of an optical pointing device, the driver circuit comprising:

a first transistor coupled to the light source at a first node;

a first current source for providing a reference current;

a second transistor coupled to the first current source and to the first transistor; and

a controller coupled to the first transistor and the light source at the first node for monitoring a first current through the light source, comparing the first current to a reference current, and generating a control signal based on a result of the comparison, wherein the control signal causes the first transistor to change the first current; and

wherein the reference current is adjusted based on the result of the comparison.

2. The driver circuit of claim 1 , wherein the driver circuit is implemented in an integrated circuit.

3. The driver circuit of claim 1 , wherein the controller is a digital controller.

4. The driver circuit of claim 1 , wherein the controller is an analog controller.

5. The driver circuit of claim 1 , wherein the controller comprises an operational amplifier.

6. The driver circuit of claim 1 , wherein the first current source is configured to receive the control signal and adjust the reference current based on the received control signal.

7. The driver circuit of claim 6 , wherein the first current source is configured to receive a current selection signal from a processor of the optical pointing device and adjust the reference current based on the current selection signal.

8. The driver circuit of claim 1 , and further comprising:

a second current source coupled to the first transistor end to the controller far receiving the control signal and changing a drive signal to the first transistor based on the received control signal, thereby causing the first transistor to change the first current.

9. The driver circuit of claim 8 , and further comprising:

a third current source for providing a drive current;

a third transistor coupled to the third current source; and

wherein the first transistor, second transistor, and third transistor are coupled together in a current mirror configuration.

10. A method of driving a light source of an optical pointing device, the method comprising:

providing a reference current;

providing at least two controlled current sources directly coupled to a controller that are responsive to control signals from the controller;

comparing a light source current through the light source with the reference current; and

continually adjusting the light source current through the light source with the controlled current sources during normal operation of the optical pointing device to match the reference current; and

adjusting the reference current based on a result of the comparison.

11. The method of claim 10 , wherein the comparison is performed by the controller.

12. The method of claim 11 , wherein the controller is an operational amplifier.

13. The method of claim 10 , wherein the step of adjusting the light source current comprises:

providing a drive transistor coupled to the light source;

providing a drive signal to the drive transistor for controlling the light source current through the light source; and

generating a control signal based on a result of the comparison that adjusts the drive signal, thereby modifying the light source current through the light source to match the reference current.

14. A method of driving a light source of an optical pointing device, the method comprising:

providing a reference current;

comparing a light source current through the light source with the reference current;

continually adjusting the light source current through the light source during normal operation of the optical pointing device to match the reference current; and

adjusting the reference current based on a result of the comparison.

Assignments (7)