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Real time LCD CCFL backlight power on time logging of multi level intensity correlated to a fixed intensity level

IP.com Disclosure Number: IPCOM000181660D
Original Publication Date: 2009-Apr-08
Included in the Prior Art Database: 2009-Apr-08
Document File: 1 page(s) / 22K

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LCD display CCFL backlight bulbs have been a source of field failures due to problems with defective backlight inverter circuits and defective CCFL bulbs. The Power On Hour (POH) total for the bulbs can be logged, but the actual POH dependes on the brightness setting (current level) of the CCFL bulb. The specified POH for a certain LCD panel CCFL bulb found in the manufacturer's datasheet is spec'd at a certain bulb current - usually Typical current or Maximum current. Actual recorded bulb POH will not compare directly with the datasheet POH intensity.

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Real time LCD CCFL backlight power on time logging of multi level intensity correlated to a fixed intensity level

This invention describes a system and method for factoring in CCFL intensity levels and correlating the POH for that intensity to the specified POH in real time. The resulting POH value recorded over time can then be directly compared with the rated POH at the specified intensity. For example, an LCD display with a CCFL spec of 30,000 POH at Typical intensity that is run at Maximum intensity may correlate to only 10,000 useful Power On Hours. In this invention, the POH accumulator would be imcremented with a value different than 1 for an hours time and this correction factor is based on the CCFL POH vs. Intensity curve supplied by the LCD panel manufacturer.

The invention consists of a micro processor, intensity level input signaling from the CCFL backlight control circuit, a CCFL bulb graph which correlates actual POH intensity to specified POH intensity, and an algorithm to record power on hours and intensity levels.

The algorithm is implemented in firmware of the micro processor, stores a look up table representing the POH/Intensity graph at certain intervals. In the general case, the firmware records the intensity level for one hour and updates a POH accumulator register every hour with the value in the look up table. For higher actual backlight settings than specified in the Specs. POH life time, the POH a...