Multi-Step Common Voltage Generator for LCD Ripple Reduction
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Solution Overview
Problem
Liquid-crystal display devices face challenges in rapidly reaching a target common voltage within a limited time, particularly due to significant ripples in common voltage caused by large variations in data voltage, which can lead to smear and crosstalk issues during image testing.
Innovation Solution
A liquid-crystal display device and driving method that utilize a multi-step common voltage generator, which outputs a target voltage and a reference level voltage within a horizontal period, allowing the common voltage to transition through a reference level to quickly reach the target level, thereby minimizing ripple and achieving efficient compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a single-step common voltage generator is used, then the device complexity is low, but the common voltage cannot reach the target voltage within a limited time due to large ripples
Solution Approach 1:
The common voltage transition process is segmented into multiple steps. Instead of transitioning directly from the initial voltage to the target voltage, the generator creates intermediate voltage levels (first common voltage, second common voltage, etc.) that progressively approach the target voltage. This segmentation allows the voltage to reach the target faster while maintaining control over the transition process, resolving the contradiction between transition speed and device complexity.
2Measurement precision
If the reference level interval is fixed, then the device complexity is low, but the common voltage cannot be accurately controlled when transition width varies
Solution Approach 1:
The reference level interval is made dynamic rather than fixed. The generator adjusts the reference level interval based on the transition width of the common voltage. When the transition width is large, a larger reference level interval is used; when the transition width is small, a smaller reference level interval is used. This dynamic adjustment enables accurate control of the common voltage under varying conditions while managing device complexity through adaptive control logic.
3Reliability
If a multi-step common voltage generator is used, then the common voltage can be quickly stabilized, but the device complexity increases
Solution Approach 1:
The common voltage generator incorporates feedback mechanisms to monitor the common voltage level and adjust subsequent voltage steps accordingly. The generator uses the actual common voltage measurement to determine the next reference level and transition step, ensuring reliable stabilization even with increased device complexity. This feedback control compensates for the added complexity by providing adaptive, self-correcting operation.
Data Source
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AI summary
A liquid-crystal display device and a driving method thereof are disclosed. The liquid crystal display device comprises: a target level generator (105) configured to output target level data during every horizontal period based on analyzed data of an input image; and a multi-step common voltage generator (120) configured to output a target voltage corresponding to the target level data and a reference level voltage corresponding to preset reference data within one horizontal period (1H) and output a common voltage (Vcom), wherein the common voltage (Vcom) is generated as first and second target voltages within first and second horizontal periods, respectively, wherein the reference level voltage is generated for a 1/2 horizontal period (1/2 H) or less, between the first and second target voltages, and is lower than the first target voltage and higher than the second target voltage.