LCD Driving Circuit Synchronizes LED Luminance with Liquid Crystal Response
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Solution Overview
Problem
Liquid crystal display (LCD) images suffer from flickering due to the limited response speed of liquid crystal materials, which causes mismatch between the change in light source luminance and optical transmittance, leading to inconsistent display luminance.
Innovation Solution
A method for driving an LCD assembly that controls the luminance of the planar light source device based on the response speed of the liquid crystal material, using pulse-width modulation of light emitting diodes (LEDs) and adjusting the light emitting start period of each planar light source unit according to its position, to synchronize with the optical transmittance changes of the pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the light source luminance is changed quickly to control display luminance, then the response speed of light source control is improved, but the liquid crystal optical transmittance cannot keep up, causing display luminance inconsistency and flickering
Solution Approach 1:
The patent applies preliminary action by controlling the light source to turn on before the liquid crystal pixels reach their target optical transmittance state. Specifically, the light source is activated in advance during the frame period, and its luminance is adjusted based on the expected optical transmittance changes of the liquid crystal material, ensuring that when the pixels reach their target state, the display luminance is already correct and stable.
Solution Approach 2:
The patent implements feedback control by using a sensor to detect the actual display luminance and comparing it with the target luminance value. The detected luminance information is fed back to the control circuit, which then adjusts the light source luminance and pixel optical transmittance to minimize the difference between actual and target display luminance, ensuring consistent and stable display output.
2Use of energy by moving object
If the light source luminance is reduced to match the pixel optical transmittance, then power consumption is reduced, but the display luminance becomes inconsistent when pixels are at different transmittance states
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting both the light source luminance parameter and the pixel optical transmittance parameter in a coordinated manner. The control circuit calculates appropriate luminance values for the light source based on the optical transmittance states of pixels, and adjusts these parameters continuously to maintain constant display luminance while optimizing power consumption.
Solution Approach 2:
The patent uses feedback control to monitor the actual display luminance and adjust the light source luminance accordingly. When pixels are at low transmittance states, the light source luminance is reduced to match, maintaining power efficiency. When pixels reach high transmittance states, the light source luminance is increased to maintain display luminance consistency, ensuring both energy efficiency and display quality.
3Ease of operation
If the light source illuminates the entire display area uniformly, then the manufacturing and operation are simplified, but the display luminance cannot be locally controlled for different display area units
Solution Approach 1:
The patent applies segmentation by dividing the display area into multiple display area units, each with its own set of pixels that can be independently controlled. The control circuit can selectively adjust the optical transmittance of pixels in different display area units, enabling local luminance control for different regions of the display while maintaining a relatively simple uniform light source structure.
4Reliability
If the light source luminance is increased to compensate for low pixel transmittance, then the display luminance is maintained, but the power consumption increases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting both the light source luminance parameter and the pixel optical transmittance parameter in a coordinated manner. The control circuit calculates appropriate luminance values for the light source based on the optical transmittance states of pixels, and adjusts these parameters continuously to maintain constant display luminance while optimizing power consumption.
Solution Approach 2:
The patent uses feedback control to monitor the actual display luminance and adjust the light source luminance accordingly. When pixels are at low transmittance states, the light source luminance is reduced to match, maintaining power efficiency. When pixels reach high transmittance states, the light source luminance is increased to maintain display luminance consistency, ensuring both energy efficiency and display quality.
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 approach prevents flickering on the LCD image by ensuring that the display luminance remains consistent and stable, even with constant input driving signals, while also reducing power consumption and enhancing color reproduction and contrast ratio.
Implementation Method 1
A method for driving an LCD assembly that controls the luminance of the planar light source device based on the response speed of the liquid crystal material, using pulse-width modulation of light emitting diodes (LEDs)
Implementation Method 2
Liquid crystal cells making up each pixel or each sub pixel are operated as a sort of light shutter (light valve), i.e., the optical transmittance of each pixel or each sub pixel is controlled
Data Source
AI summary
A method driving an LCD assembly, the LCD assembly including a transmission-type LCD including a display area configured of pixels, a planar-light-source device illuminating the display area, and a driving circuit driving the planar-light-source device and LCD; wherein the driving circuit supplies a control signal controlling the optical transmittance of each pixel to each pixel, the method comprising, for each frame with LCD image display, the steps of: controlling the luminance of the planar-light-source device by the driving circuit such that, when assuming that the control signal equivalent to a driving signal having the maximum value of driving signals input to the driving circuit driving all the pixels making up the display area is supplied to a pixel, the luminance of the pixel is obtained; and controlling the luminance of the planar-light-source device by the driving circuit based on the response speed of a liquid-crystal material making up the pixels.