LED driving apparatus and method of controlling luminous power

• US 20060082538A1
• Filed: 10/03/2005
• Published: 04/20/2006
• Est. Priority Date: 10/08/2004
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Oyama, Yoshiki
• Granted Patent: US 7,916,101 B2
• Time in Patent Office: Days
• US Class Current: 345/102
• CPC Class Codes: G09G 2320/0606 Manual adjustment
• CPC Class Codes: G09G 2320/0633 by amplitude modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: H05B 45/12 using optical feedback
• CPC Class Codes: H05B 45/375 using buck topology

Abstract

A light emitting diode (LED) driving apparatus includes a drive section for driving an LED to emit light, and a control section that controls a driving current supplied from the drive section to the LED. The control section implements luminous power control by controlling an ON/OFF ratio of the driving current if a target value of luminous power of the LED is smaller than a predetermined value. The control section implements luminous power control by controlling a level of the driving current if the target value is equal to or larger than the predetermined value.

Claims

1. A light emitting diode (LED) driving apparatus, comprising:

drive means for driving an LED to emit light; and

control means that controls a driving current supplied from the drive means to the LED, the control means implementing luminous power control by controlling an ON/OFF ratio of the driving current if a target value of luminous power of the LED is smaller than a predetermined value, the control means implementing luminous power control by controlling a level of the driving current if the target value is equal to or larger than the predetermined value.

2. The LED driving apparatus according to claim 1, wherein the predetermined value is set based on luminous power obtained from a driving current value that provides a highest luminous efficiency of the LED.

3. The LED driving apparatus according to claim 1, wherein in the luminous power control implemented by controlling the ON/OFF ratio of the driving current, the level of the driving current is kept constant at a driving current value that provides a highest luminous efficiency of the LED.

4. The LED driving apparatus according to claim 1, wherein the control means stores correspondence information relating to the target value and the ON/OFF ratio, and relating to the target value and the driving current value, the control means implementing the luminous power control by setting the ON/OFF ratio or the driving current value associated with the target value in the correspondence information.

5. The LED driving apparatus according to claim 1, further comprising:

luminous power detection means that detects luminous power of the LED, wherein the control means implements the luminous power control by controlling the ON/OFF ratio or the driving current value so that a value of the luminous power detected and input by the luminous power detection means equals the target value.

6. A method of controlling the luminous power of an LED, the method comprising:

controlling an ON/OFF ratio of a driving current if a target value of the luminous power of the LED is smaller than a predetermined value; and

controlling a level of the driving current if the target value is equal to or larger than the predetermined value.

7. A light emitting diode (LED) driving apparatus, comprising:

a drive section for driving an LED to emit light; and

a control section that controls a driving current supplied from the drive section to the LED, the control section implementing luminous power control by controlling an ON/OFF ratio of the driving current if a target value of luminous power of the LED is smaller than a predetermined value, the control section implementing luminous power control by controlling a level of the driving current if the target value is equal to or larger than the predetermined value.

8. Liquid crystal display apparatus, comprising:

a liquid crystal display panel;

a panel drive section for driving the liquid crystal display panel based on an image input signal;

a light emitting diode (LED) as a light source for the liquid crystal display panel;

a drive section for driving the LED to emit light; and

a control section that controls a driving current supplied from the drive section to the LED, the control section implementing luminous power control by controlling an ON/OFF ratio of the driving current if a target value of luminous power of the LED is smaller than a predetermined value, the control section implementing luminous power control by controlling a level of the driving current if the target value is equal to or larger than the predetermined value.