LED Backlight Driving Circuit Bypass Failure
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Solution Overview
Problem
In liquid crystal display devices, a malfunctioning light emitting diode in a backlight assembly's string causes the entire string to turn off, leading to degraded picture quality and loss of functionality.
Innovation Solution
A backlight assembly driving apparatus with serially connected light emitting diodes and parallel switching devices that redirect current from a malfunctioning diode to adjacent diodes, ensuring continuous operation and maintaining picture quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If light emitting diodes are connected in series to form a backlight assembly, then the structure is simple and manufacturing is easy, but a single malfunctioning diode causes the entire string to turn off
Solution Approach 1:
The patent divides the backlight assembly into multiple independent modules, each containing a subset of LED strings. Each module has its own driving circuit that can independently control and compensate for failures in individual strings. This segmentation allows the system to maintain partial functionality even when some LEDs fail, resolving the reliability issue while preserving manufacturing simplicity.
Solution Approach 2:
The patent implements dynamic adjustment of driving parameters (current, voltage, pulse width modulation duty cycle) based on the operational status of individual LED strings. When a malfunction is detected, the system changes operating parameters to redistribute power and maintain backlight performance, thereby improving reliability without complicating the basic series connection structure.
2Reliability
If switching devices are added in parallel to each light emitting diode to prevent malfunction, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent combines the switching device with the existing LED package structure, integrating the switch into the same physical housing or mounting substrate. This merging approach adds the necessary switching functionality for reliability while minimizing the increase in overall device complexity by sharing common components and space.
Solution Approach 2:
The switching device is designed to serve multiple functions: it acts as a bypass switch for failed LEDs, a protection device for overcurrent conditions, and a control element for dimming operations. This multi-functionality justifies the added complexity by providing multiple reliability and control benefits from a single component addition.
Data Source
AI summary
A backlight assembly driving apparatus for a liquid crystal display device includes a light emitting diode string of serially connected light emitting diodes, and switching devices connected in parallel to and in a one-to-one correspondence with the light emitting diodes to conduct or turn off current applied to a correspondingly parallel-connected light emitting diode.