EL Panel Pre-Charging Circuit Uniformity
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Solution Overview
Problem
Existing electro-luminescence display panels face challenges in pre-charging storage capacitors within a desired time, especially for low gray levels, due to issues with current source accuracy, voltage drop variations, and insufficient discharge currents, leading to non-uniform charging and prolonged charging times.
Innovation Solution
A two-step pre-charging method using a pre-charge voltage source followed by a floating method to pre-charge storage capacitors, where the first step applies a pre-charge voltage and the second step discharges to a constant threshold voltage, compensating for voltage drops and ensuring uniform charging across the panel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a current source is used to pre-charge the storage capacitor, then the charging process can be initiated, but the charging time becomes excessively long and the charging is non-uniform due to insufficient discharge current and voltage drop variations
Solution Approach 1:
The patent applies a preliminary action by pre-charging the storage capacitor to a first pre-charge voltage before the normal charging process. This preliminary charging step prepares the capacitor in advance, reducing the time required for subsequent charging operations and ensuring uniform voltage distribution across all pixels regardless of their location in the display panel.
Solution Approach 2:
The patent changes the voltage parameter by introducing a two-stage pre-charge voltage system. The storage capacitor is first charged to a first pre-charge voltage, then adjusted to a second pre-charge voltage that compensates for voltage drops. This parameter change ensures uniform charging across the panel and resolves the contradiction between charging speed and charging uniformity.
2Use of energy by stationary object
If the storage capacitor is charged to a low gray level voltage, then power consumption is reduced, but the charging time becomes excessively long due to insufficient discharge current
Solution Approach 1:
The patent performs a preliminary charging action to a first pre-charge voltage before the final charging to the target gray level voltage. This preliminary step ensures that even when charging to low gray levels (which require small voltage differences and thus small currents), the capacitor is adequately prepared in advance, preventing excessively long charging times while maintaining low power consumption.
Solution Approach 2:
The patent introduces a two-level voltage parameter system where the storage capacitor is first charged to a higher first pre-charge voltage, then adjusted to a lower second pre-charge voltage corresponding to the target gray level. This parameter change strategy allows sufficient discharge current during the first stage to reduce charging time, while the second stage maintains the low voltage required for low power consumption.
3Device complexity
If a simple charging method is used, then the device complexity is low, but the charging time cannot be controlled within the desired time frame
Solution Approach 1:
The patent implements a preliminary charging action using a pre-charge voltage source connected through a switch to the storage capacitor. This adds minimal circuit complexity (one additional voltage source and switch) but achieves significant time reduction by pre-charging the capacitor before the normal charging process, ensuring charging completes within the desired time frame.
Solution Approach 2:
The patent segments the charging process into two distinct stages: a first pre-charge stage to a first pre-charge voltage, and a second charging stage to the final target voltage. This segmentation allows each stage to be optimized independently - the first stage provides rapid initial charging with sufficient current, while the second stage completes the charging precisely, together ensuring the total charging time meets requirements without excessive circuit complexity.
Data Source
AI summary
An electro-luminescence (EL) display device includes an electro-luminescence display panel including a plurality of pixels arranged in a matrix form at pixel areas defined by intersections between gate lines and data lines, each of the pixels having an EL cell connected to a first voltage source and a cell driver, the cell driver connected to a respective one of the gate lines and a respective one of the data lines and connected between a second voltage source and the EL cell, and a pre-charger for pre-charging a storage capacitor in the cell driver into a first pre-charge voltage using a pre-charge voltage source and then floating the respective data line in a pre-charge period prior to an application of a data signal, thereby arriving at a second pre-charge voltage by a discharge of the first pre-charge voltage of the storage capacitor.