BACKLIGHT MODULE FOR DISPLAYS

• US 20090267530A1
• Filed: 04/22/2009
• Published: 10/29/2009
• Est. Priority Date: 04/23/2008
• Status: Active Grant

• Current Assignee: InnoLux Corporation
• Original Assignee: Chi Mei Optoelectronics (InnoLux Corporation)
• Inventors: Wu, Cheng-I, Yang, Cheng-Feng, Huang, Shih-Pin
• Granted Patent: US 8,760,383 B2
• Time in Patent Office: Days
• US Class Current: 315/250
• CPC Class Codes: H05B 45/37 Converter circuits

Abstract

A backlight module includes a light-emitting unit, and a controller to receive a first control signal and generate a second control signal to control the light-emitting unit. The controller controls a frequency of the second control signal according to a duty cycle of the first control signal.

Claims

1. An apparatus comprising:

a backlight module comprising;

a light-emitting unit; and

a controller to receive a first control signal and generate a second control signal to control the light-emitting unit, the controller controlling a frequency of the second control signal according to a duty cycle of the first control signal.

2. The apparatus of claim 1 in which the controller causes the second control signal to have a first frequency or a second frequency based on a comparison of the duty cycle of the first control signal and a first threshold value.

3. The apparatus of claim 2 in which the first threshold value is between 15% to 25%.

4. The apparatus of claim 2 in which the first frequency is between 180 Hz to 220 Hz.

5. The apparatus of claim 4 in which the second frequency is between 9 KHz to 11 KHz.

6. The apparatus of claim 1 in which the controller causes the second control signal to have a first frequency, a second frequency, or a third frequency based on a comparison of the duty cycle of the first control signal and a first threshold value and a second threshold value.

7. The apparatus of claim 1 in which the average luminance of the light-emitting unit varies according to the duty cycle of the second control signal.

8. The apparatus of claim 1 in which the first control signal and the second control signal have the same duty cycle.

9. The apparatus of claim 1 in which the light-emitting unit comprises a plurality of light-emitting diodes and a current regulator to regulate currents that pass the light-emitting diodes.

10. The apparatus of claim 9 in which the second control signal controls the current regulator in regulating the currents.

11. The apparatus of claim 1, further comprising a liquid crystal display panel that is illuminated by the backlight module.

12. An apparatus comprising:

a light source comprising;

a light-emitting unit; and

a controller to receive a first control signal and generate a second control signal to control the light-emitting unit, the controller controlling a frequency of the second control signal according to a duty cycle of the first control signal; and

a reflective display device that is illuminated by the light source.

13. A method for driving a backlight module comprising a light-emitting unit, the method comprising:

receiving a first control signal;

determining whether a duty cycle of the first control signal is larger than or equal to a first threshold value;

outputting a second control signal having a first frequency to a light-emitting unit if the duty cycle of the first control signal is larger than or equal to the first threshold value; and

outputting a second control signal having a second frequency to the light-emitting unit if the duty cycle of the first control signal is smaller than the first threshold value.

14. The method of claim 13 in which the first control signal and the second control signal have the same duty cycle.

15. The method of claim 13 in which the first threshold value is between 15% to 25%.

16. The method of claim 13 in which the first frequency is between 180 Hz to 220 Hz.

17. The method of claim 13 in which the second frequency is between 9 KHz to 11 KHz.

18. The method of claim 13, further comprising, if the duty cycle of the first control signal is smaller than the first threshold value, determining whether the duty cycle of the first control signal is larger than or equal to a second threshold value that is smaller than the first threshold value,

outputting the second control signal having the second frequency to the light-emitting unit if the duty cycle of the first control signal is larger than or equal to the second threshold value, and

outputting the second control signal having a third frequency to the light-emitting unit if the duty cycle of the first control signal is less than the second threshold value.

19. A liquid crystal display, comprising:

a liquid crystal display panel having a plurality of pixels;

a light-emitting unit to generate light to illuminate the pixels; and

a frequency controller to receive a first control signal and generate a second control signal that is sent to the light-emitting unit to control an average luminance of the light-emitting unit, the second control signal alternating between high and low levels and having a first frequency if a duty cycle of the first control signal is greater than or equal to a threshold value, the second control signal having a second frequency if the duty cycle of the first control signal is less than the threshold value, the light-emitting unit emitting light according to a frequency and duty cycle that correspond to the frequency and duty cycle of the second control signal.

20. The display of claim 19 in which the first control signal and the second control signal have the same duty cycle.