LED Array Junction Temperature Control in LCD Backlighting
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Solution Overview
Problem
Liquid crystal displays require efficient backlighting to produce a visible image, but existing control methods for LED arrays in these displays often result in reduced luminance and increased image blur at varying temperatures, making them difficult to read in extreme conditions.
Innovation Solution
A control module with a processor and memory that adjusts the LED array's luminance based on junction temperature, using a method with multiple stages to optimize power usage and image brightness, including preheating, maximum luminance, and power reduction strategies to extend the display's operating temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the LED array operates at maximum luminance continuously, then the display brightness is maintained, but the junction temperature increases causing reduced luminance and image blur
Solution Approach 1:
The patent implements periodic action by alternating between high-current pulses (for rapid heating) and lower-current operation (for maintenance), creating a cyclical pattern that prevents excessive temperature accumulation while maintaining display brightness. The control module switches between different current levels based on temperature feedback.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the LED operating parameters (current, voltage, duty cycle) based on the measured junction temperature. The system modifies these parameters in real-time to optimize both brightness and temperature management, transitioning between different operational states.
2Illumination intensity
If the LED array uses high current to maintain brightness, then illumination intensity is improved, but energy consumption increases
Solution Approach 1:
The system uses periodic high-current pulses rather than continuous high current, reducing overall energy consumption while maintaining perceived brightness. The duty cycle modulation allows the LED to operate at high intensity only when necessary for temperature management and brightness maintenance.
Solution Approach 2:
The control module dynamically changes operating parameters based on temperature and brightness requirements, optimizing the balance between luminance and power consumption. By adjusting current, voltage, and duty cycle parameters adaptively, the system achieves energy efficiency without sacrificing display quality.
3Temperature
If the LED array operates at low temperature, then junction temperature is controlled, but the liquid crystal layer responds slowly reducing image clarity
Solution Approach 1:
The patent applies preliminary action by using initial high-current pulses to rapidly heat the LED junction and surrounding components, including the liquid crystal layer, to an optimal operating temperature range before normal operation begins. This pre-heating phase ensures fast response times are achieved early in the operation cycle.
Solution Approach 2:
The system uses short, intensive high-current pulses that rapidly skip through the temperature ramp-up phase, quickly bringing the liquid crystal layer to its optimal response temperature without prolonged exposure to temperatures that would cause degradation or excessive power consumption.
Data Source
AI summary
A display assembly includes a display unit having a liquid crystal layer and an LED array configured to illuminate the liquid crystal layer. A driver circuit is operatively connected to the LED array and configured to control a luminance of the LED array. A control module is operatively connected to the display unit and includes a processor and tangible, non-transitory memory on which is recorded instructions for executing a method for controlling the LED array in the display unit. The control module is programmed to obtain a junction temperature (TJ) of the LED array, via the driver circuit. The junction temperature (TJ) is based at least partially on a first voltage (V1), a second voltage (V2) and a predetermined coefficient (Tcoefficient). The control module may be programmed to enter one of a plurality of stages based at least partially on the junction temperature (TJ).