Reference Driver Circuit Calibration for Display Uniformity
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Solution Overview
Problem
Current-addressed display devices face challenges in achieving uniformity of light output due to variations in transistor characteristics, leading to non-uniformity in pixel brightness across the display array, particularly exacerbated by the use of low temperature polysilicon or amorphous silicon technologies which hinder the production of uniform current source circuits.
Innovation Solution
The implementation of a calibration method using a reference driver circuit to adjust and synchronize the output of controllable driver circuits, ensuring that at least one driver circuit is calibrated while others provide inputs, thereby reducing the spread of driver circuit outputs and improving current or voltage matching across the display array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional current source circuits are used in active matrix display devices, then the display can be manufactured using low temperature polysilicon or amorphous silicon technologies, but the transistor characteristic variations cause non-uniformity in pixel brightness across the display array
Solution Approach 1:
The patent implements a feedback mechanism where a reference driver circuit generates a reference signal that is fed back to adjust and calibrate the controllable driver circuits. This feedback loop compensates for transistor characteristic variations by dynamically adjusting driver circuit outputs based on the reference signal, thereby achieving uniform pixel brightness across the display array while maintaining compatibility with low temperature polysilicon or amorphous silicon manufacturing processes
Solution Approach 2:
The patent changes the operating parameters of the driver circuits by introducing a reference driver circuit that generates calibration signals. These signals modify the electrical parameters (such as current or voltage levels) of the controllable driver circuits to compensate for manufacturing variations. By dynamically adjusting these parameters through the reference circuit, the system achieves improved brightness uniformity without requiring stricter manufacturing controls
2Ease of operation
If multiple driver circuits are used to provide inputs to all data conductors, then the display can be fully addressed, but the spread in driver circuit outputs causes non-uniformity in current or voltage matching across the display array
Solution Approach 1:
The patent introduces a reference driver circuit as an intermediary element that mediates between the input signals and the multiple controllable driver circuits. This reference circuit generates a common reference signal that all controllable driver circuits use for calibration, ensuring they operate from a unified baseline. This intermediary reference signal compensates for individual driver circuit variations, achieving uniform current or voltage matching across all data conductors while maintaining full display addressing capability
3Manufacturing precision
If a reference driver circuit is added to calibrate controllable driver circuits, then the uniformity of light output is significantly improved, but the device complexity increases
Solution Approach 1:
The patent merges the reference driver circuit functionality with the existing driver circuit architecture by integrating it into the same data conductor addressing system. The reference driver circuit is combined with the controllable driver circuits to share common components such as data conductors and timing control, reducing the overall complexity increase. This merging approach allows calibration functionality to be added without requiring completely separate hardware systems
Solution Approach 2:
The reference driver circuit is designed to perform multiple functions: it generates reference signals for calibration, provides timing control for the calibration process, and serves as a template for the controllable driver circuits. This multi-functionality reduces the need for additional dedicated components, as the reference circuit serves several purposes simultaneously, thereby limiting the increase in device complexity while achieving improved pixel brightness uniformity
Data Source
AI summary
A display device has an array of display elements (2) each driven by an input provided on a data conductor (6). These inputs are generated by data conductor addressing circuitry (9) which has a plurality of controllable driver circuits (32,34,40), each for providing an input to an associated data conductor. The number of controllable driver circuits is at least one greater than the number required for providing data to all data conductors. A reference driver circuit (30) is used for calibrating at least one of the controllable driver circuits whilst the other controllable driver circuits provide inputs to the data conductors. This provides a reduction in the spread of driver circuit outputs by calibration of the driver circuits using a reference driver circuit.