Display Device Current Measurement During Pause Periods
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Solution Overview
Problem
Existing active matrix-type display devices face challenges in measuring current for pixel circuits without reducing image quality, particularly due to irregular data transfer timing and the need for frame or line memories, and the measurement voltage affecting average luminance of organic EL elements.
Innovation Solution
The implementation of a display device with a scanning line drive circuit and a data line drive circuit that measure currents during a pause period, allowing for separate voltage application and current measurement, and using a shift register to control scanning signals, enabling efficient current measurement without impacting image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current measurement is performed during the video signal period using the conventional method, then current can be measured for pixel circuits, but the timing of data transfer becomes irregular and frame memory or line memory is required
Solution Approach 1:
The patent divides the frame period into a video signal period and a vertical flyback period, and further segments the vertical flyback period into multiple pause periods. Current measurement is performed during these pause periods within the vertical flyback period, separating the measurement function from the data transfer function and eliminating the need for additional frame memory or line memory.
Solution Approach 2:
The patent performs current measurement during the vertical flyback period's pause periods, which are predetermined time slots allocated for this purpose. By preparing and utilizing these pause periods in advance, the system can measure current without interfering with the main video signal transmission timing, thus avoiding irregular data transfer timing.
2Measurement precision
If measurement voltage is written to pixel circuit during current measurement, then current can be measured, but average luminance of organic EL element changes and image quality is reduced
Solution Approach 1:
The patent utilizes the periodic pause periods within the vertical flyback period to perform current measurement. During these specific time slots, measurement voltage is applied to pixel circuits, while during other periods, normal data voltages are transmitted. This periodic alternation allows current measurement without continuously affecting the luminance, as measurement occurs only during designated pause intervals when display is not active.
Solution Approach 2:
The patent applies measurement voltage to pixel circuits during the pause periods of the vertical flyback period, which are predetermined time slots before the next video signal period begins. By performing the measurement voltage application in advance during these allocated pause periods, the system measures current without interfering with the subsequent display period's luminance output.
3Use of energy by moving object
If pause driving is implemented, then power consumption is reduced, but transistors must have excellent off-leakage characteristics
Solution Approach 1:
The patent utilizes the existing pause periods in the vertical flyback period to perform current measurement, eliminating the need for additional pause driving implementation. The measurement function serves itself by utilizing the already-existing pause time structure, thereby reducing power consumption without requiring transistors to have enhanced off-leakage characteristics beyond what is already needed for standard pause driving operation.
Data Source
AI summary
In a current measurement period set in a pause period, a display device of the present invention applies measurement voltages to data lines (S1 to Sm) and measures currents outputted to monitoring lines (M1 to Mm) from m pixel circuits (18), and then applies data voltages generated corresponding to video signals to the data lines (S1 to Sm).