Timing-Based ADC Circuit for AMOLED Pixel Compensation
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Solution Overview
Problem
Conventional analog-to-digital conversion methods in AMOLED displays lack accuracy, leading to non-uniform OLED light emission due to variations in driving current caused by TFT instability and aging, which affects external electrical compensation.
Innovation Solution
An ADC circuit comprising an operational amplifier, integral capacitor, comparator, and timer, which converts an analog current signal to a digital signal with high accuracy by using a timing operation and level conversion, and includes a reset and timing-control sub-circuit for precise data generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional analog-to-digital conversion methods are used in AMOLED displays, then the device complexity is reduced, but the measurement precision of the analog current signal deteriorates, leading to non-uniform OLED light emission
Solution Approach 1:
The ADC circuit is segmented into distinct functional modules: an integral circuit for signal integration, a comparator for threshold comparison, and a timer for duration measurement. This segmentation allows each module to perform its specific function with high precision while maintaining overall circuit manageability and reducing complexity through functional decomposition.
Solution Approach 2:
The patent introduces an integral circuit as an intermediary between the analog current signal input and the digital output. This intermediary converts the analog current signal into a voltage signal through integration, which can then be accurately compared by the comparator and measured by the timer, thereby improving measurement precision without requiring a complex direct ADC structure.
2Stability of the object's composition
If external electrical compensation is performed without accurate analog-to-digital conversion, then the device complexity is reduced, but the light-emission uniformity deteriorates due to driving current variations
Solution Approach 1:
The ADC circuit provides accurate feedback of the analog current signal magnitude through precise analog-to-digital conversion. This feedback enables the external electrical compensation circuit to adjust driving parameters accurately, compensating for TFT instability and aging effects, thereby maintaining light-emission uniformity across the display panel.
Solution Approach 2:
The patent replaces complex mechanical or analog compensation mechanisms with an electronic ADC-based system. By converting the analog current signal to digital form with high precision, the system enables software-based or digital logic-based compensation algorithms, which are more accurate and stable than traditional analog compensation methods.
3Reliability
If a simple conversion circuit is used, then the ease of manufacture is improved, but the reliability of the compensation process deteriorates due to conversion inaccuracies
Solution Approach 1:
The patent changes the operational parameters of the conversion process by using integration time and threshold voltage comparison instead of direct analog-to-digital conversion. The timer measures the integration duration until the voltage reaches a threshold, converting the analog signal magnitude into a digital time-based measurement. This parameter transformation improves reliability while keeping the circuit structure relatively simple and manufacturable.
Data Source
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AI summary
The present application discloses an analog-to-digital conversion (ADC) circuit. The circuit includes an integral circuit including an operational amplifier and an integral capacitor. The circuit further includes a comparator and a timer. The operational amplifier includes a positive input terminal configured to receive a first voltage, a negative input terminal coupled to a signal-collection line configured to collect an analog current signal, and an output terminal configured to output a first output signal. The comparator is configured to compare the first output signal with a second voltage to generate a second output signal to the timer. The timer is configured to start a timing operation when the operational amplifier receives the analog current signal and end the timing operation when the second output signal changes. A binary data resulted from the timing operation characterizes a digital signal corresponding to the analog current signal.