Pixel Current Measurement in Active Matrix Display Devices
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Solution Overview
Problem
Existing display technologies face challenges in accurately measuring pixel current during image display due to the effects of aging drive TFTs and organic EL elements, with measurement difficulties caused by distributed constant circuits and leakage currents, leading to inconsistencies in brightness and prolonged measurement times.
Innovation Solution
An active matrix display device with horizontal power supply lines and switches that allow for selective power supply connection to each horizontal line, enabling pixel current measurement during normal image display by isolating non-measured lines and using feedback control for accurate A/D conversion output, thereby reducing leakage current and parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel current is measured during image display, then measurement can be performed in real time to correct brightness inconsistencies, but leakage current from unselected pixels and distributed constant circuits contaminates the measurement
Solution Approach 1:
The display panel's power supply system is segmented into multiple independent horizontal power supply lines, each controllable separately. During pixel current measurement, only the power supply line corresponding to the selected horizontal line is activated, while other power supply lines are turned off. This segmentation isolates the measurement circuit from leakage currents of unselected pixels and reduces the impact of distributed constant circuits, enabling accurate pixel current measurement during image display.
2Measurement precision
If traditional current measurement methods are used, then all pixels remain powered during measurement, but measurement time increases and accuracy decreases due to accumulated leakage current
Solution Approach 1:
The power supply system dynamically adjusts the power state of horizontal power supply lines based on measurement requirements. During pixel current measurement, the system selectively activates only the power supply line corresponding to the current measurement target, while deactivating other power supply lines. This dynamic power management reduces total leakage current and enables faster, more accurate measurements without requiring prolonged measurement periods.
3Measurement precision
If switches are added to control power supply lines, then pixel current measurement accuracy improves, but device complexity increases
Solution Approach 1:
The switches controlling horizontal power supply lines serve multiple functions: they enable accurate pixel current measurement by isolating selected lines, reduces leakage current effects, and maintain normal display operation. By designing the power supply control circuit to handle both measurement and display functions through the same switch infrastructure, the patent achieves measurement precision improvement without proportionally increasing device complexity.
Data Source
AI summary
During image display, pixel current measurement for brightness irregularity correction is carried out. Display is carried out by sequentially writing pixel data in a horizontal direction to pixel sections that are arranged in a matrix shape. Horizontal power supply lines PVDD are arranged for each horizontal line, and power is supplied from these power supply lines to corresponding pixel sections. When carrying out measurement of pixel current by lighting pixel sections one at a time, a horizontal power supply line PVDD of a horizontal line to which the lit pixel belongs is connected to a power supply PVDDb by a switch, and other horizontal power supply lines PVDD are connected to PVDDa.