Backlight Assembly Current Detection Circuit
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Solution Overview
Problem
Existing backlight assemblies using cold cathode fluorescent lamps (CCFLs) face issues with high voltage requirements, limited color reproducibility, and environmental concerns, while LED-based assemblies need effective error detection for current deviations between light source strings.
Innovation Solution
A backlight assembly incorporating a plurality of light source strings, a driving circuit, and a current detection circuit that compares received currents with a reference current to detect errors and control the driving circuit, preventing open or short states in the light source strings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If LED-based light sources are used in backlight assemblies, then power consumption is reduced and color reproducibility is improved, but current deviation between light source strings occurs causing reliability issues
Solution Approach 1:
The patent implements a feedback mechanism where the driving circuit receives feedback voltages from each light source string through respective channel terminals. The controller adjusts the driving voltage based on this feedback to maintain consistent current across all light source strings, thereby resolving the current deviation issue while preserving LED energy efficiency
Solution Approach 2:
The patent replaces physical current measurement methods with electrical voltage feedback and computational current calculation. By measuring voltage drops across sensing resistors and calculating currents through Ohm's law, the system achieves reliable current monitoring without direct mechanical current sensing, ensuring reliability in LED backlight assemblies
2Productivity
If multiple light source strings are connected in parallel to reduce power consumption, then energy efficiency is improved, but current deviation between strings causes errors that are difficult to detect
Solution Approach 1:
The patent divides the backlight assembly into multiple independent light source strings, each with its own channel terminal and sensing resistor. This segmentation allows individual monitoring of each string's current through dedicated voltage feedback paths, making current deviations detectable while maintaining the energy efficiency benefits of parallel LED connections
Solution Approach 2:
The patent introduces sensing resistors as intermediary elements in each light source string's circuit path. These resistors convert current information into measurable voltage signals that can be fed back to the controller, enabling indirect but accurate detection of current deviations without disrupting the parallel LED configuration
Data Source
AI summary
A backlight assembly includes; a plurality of light source strings which receive a driving voltage to generate a light, a driving circuit including a channel terminal commonly connected to output terminals of the plurality of light source strings and which receives a feedback voltage through the channel terminal to control the driving voltage according to the feedback voltage, and a current detection circuit connected to the output terminals of the plurality of light source strings to receive currents from the plurality of light source strings and which turns off the driving circuit when at least one of the received currents is larger than a predetermined reference current.