LED Backlighting with Bypass Switches for Thermal Management
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Solution Overview
Problem
Electronic devices with liquid crystal displays face challenges in thermal management and energy efficiency due to the large number of LEDs used in backlight units, which can lead to thermal stress and energy loss, especially when attempting to achieve high dynamic range and improved contrast in image display.
Innovation Solution
The implementation of multiple LED matrix drivers with phase lock loops for synchronization, dedicated bypass switches for individual LEDs, and headroom voltage control circuitry to reduce energy loss and enhance display efficiency by allowing zone-by-zone brightness control and minimizing residual voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple LEDs are used in backlight units to achieve high dynamic range and improved contrast, then display quality is improved, but thermal stress and energy loss increase
Solution Approach 1:
The backlight unit is divided into multiple independently controllable LED strings or zones. Each string can be controlled separately through pulse-width modulation (PWM) or current control, allowing selective dimming or turning off of specific zones. This segmentation enables local brightness adjustment, reducing overall energy consumption while maintaining high dynamic range and contrast in displayed images.
Solution Approach 2:
The backlight system implements dynamic control where LED brightness is adjusted in real-time based on image content requirements. Different zones can have different brightness levels dynamically changed frame-by-frame or even within a single frame, optimizing energy usage while achieving high dynamic range display performance.
2Illumination intensity
If multiple LEDs are used in backlight units to achieve high dynamic range and improved contrast, then display quality is improved, but thermal stress increases
Solution Approach 1:
By dividing the backlight into multiple independently controllable zones or strings, the patent enables selective activation of LED groups. This reduces the total number of LEDs operating simultaneously, thereby lowering cumulative heat generation and thermal stress on the display system while maintaining high dynamic range capabilities.
Solution Approach 2:
The system uses pulse-width modulation (PWM) to control LED brightness by rapidly switching LEDs on and off at different duty cycles. This periodic operation allows LEDs to operate in brief pulses rather than continuous operation, reducing average power consumption and heat generation while maintaining perceived brightness levels for high dynamic range display.
3Productivity
If zone-by-zone brightness control is implemented, then display efficiency is improved, but device complexity increases
Solution Approach 1:
The backlight is divided into multiple zones or strings that can be independently controlled. Each zone can be adjusted for different brightness levels based on local image content requirements, improving overall display efficiency and energy utilization while enabling high dynamic range performance.
Solution Approach 2:
Multiple LED strings are controlled through integrated control circuitry that manages zone-by-zone brightness adjustment. The control system combines signals from image processing with backlight control to coordinate LED activation across different zones, achieving efficient local dimming while maintaining manageable system complexity through unified control architecture.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution reduces thermal stress and energy loss, improves display efficiency, and enables high dynamic range and enhanced contrast by allowing precise control of LED brightness, leading to improved image quality and reduced power consumption.
Implementation Method 1
The backlight unit commonly includes one or more light-emitting diodes (LEDs) that generate light that exits the backlight toward the liquid crystal display unit
Data Source
AI summary
Aspects of the subject technology relate to display of an electronic device. The display includes a backlight unit having a voltage source, a string of light-emitting diodes and a bypass switch for each light-emitting diode in the string. The string of light-emitting diodes can receive, at a first end, a supply voltage from the voltage source. The bypass switch for each light-emitting diode is controllable to pulse-width-modulate that light-emitting diode. The headroom voltage feedback circuit is coupled to a second end of the string.