Current Sensing Device for OLED Offset Error Reduction
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Solution Overview
Problem
Current sensing technologies in organic light-emitting display devices are prone to noise and offset errors, which distort sensing results and hinder accurate compensation of driving characteristics in OLEDs and TFTs, affecting image quality.
Innovation Solution
A current sensing device with multiple sensing units, each comprising a reference current generator, a current comparator, and an edge-triggered data flip-flop, which generates a digital sensing value by comparing pixel current with a reference current and removes offset deviations using a reset current, thereby reducing noise and offset errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a current integrator is used for sensing pixel current, then sensing speed is improved and low current sensing is enabled, but noise and offset errors increase causing sensing result distortion
Solution Approach 1:
The sensing operation is divided into two distinct phases: an integration phase where the pixel current is accumulated over time, and a reading phase where the accumulated charge is measured. This segmentation allows the system to benefit from both high-speed integration and accurate measurement while minimizing noise impact by confining it to specific time windows.
Solution Approach 2:
The current integrator performs preliminary integration of the pixel current during a designated integration period before the actual sensing/reading operation. By accumulating the current in advance, the system converts a potentially noisy continuous signal into a discrete charge quantity that can be measured with higher precision, effectively preparing the signal for accurate detection.
2Measurement precision
If multiple current integrators are equipped for per sensing channel, then sensing performance is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The current integrator is designed as a multi-functional unit that can serve multiple sensing channels sequentially. By time-multiplexing the integrator across different channels, the system achieves the sensing performance of multiple integrators while using fewer physical devices, thereby reducing complexity and manufacturing cost while maintaining measurement precision.
Solution Approach 2:
Multiple sensing channels share a common current integrator resource rather than each channel having a dedicated integrator. The integrator is sequentially allocated to different channels during their respective sensing periods, merging the sensing functions into a single versatile unit that reduces overall device complexity while preserving sensing accuracy for each channel.
3Measurement precision
If external compensation scheme is used to compensate driving characteristics changes, then image quality is improved, but additional sensing operations and time are required
Solution Approach 1:
The current integrator continuously accumulates pixel current during the integration period without interruption, maintaining a continuous useful action that captures the total charge. This continuous integration approach enables accurate sensing of driving characteristic changes while minimizing idle time and optimizing the use of available sensing windows, thereby reducing overall sensing time while maintaining image quality.
Solution Approach 2:
The sensing operation is structured as periodic alternating phases of integration and reading. During the integration phase, the integrator continuously accumulates current; during the reading phase, the accumulated charge is measured and the integrator is reset. This periodic structure enables efficient time management, allowing accurate compensation sensing to be performed in dedicated time slots without continuously occupying the sensing channel, thus reducing loss of time while maintaining image quality.
Data Source
AI summary
The current sensing device in the present disclosure comprises a plurality of sensing units each of which is connected to a sensing channel. The sensing unit may comprise a reference current generator generating a reference current; a current comparator outputting a comparator output signal based on a pixel current input through the sensing channel and the reference current, and removing an offset deviation component included in the pixel current and the reference current by using a reset current externally applied; and an edge triggered data flip-flop outputting a digital sensing value corresponding to the pixel current based on the comparator output signal.