Organic EL Drive Circuit IC Reset Voltage Equalization
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Solution Overview
Problem
Luminance unevenness in the low tone region of organic EL display panels driven by current tone systems is significant due to variations in reset voltage between drive circuit ICs, leading to conspicuous differences in luminance, especially in border areas where drive current is small.
Innovation Solution
An organic EL drive circuit IC with a reset voltage generator circuit that produces a constant voltage for resetting capacitors or organic EL elements, and a network of reset switches controlled by timing signals to synchronize and equalize reset voltages across adjacent drive circuit ICs, ensuring uniform luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a voltage drive circuit is used for the low tone region, then luminance unevenness is reduced, but the circuit size of the drive circuit is increased
Solution Approach 1:
The patent combines the reset voltage generator circuit with the existing current drive circuit architecture. The reset voltage generator is integrated into the drive circuit IC, and its output is shared across multiple pixel circuits through common wiring, allowing voltage-based reset functionality to be merged with current-based drive operations without requiring completely separate circuit paths.
Solution Approach 2:
The reset voltage is generated and applied to pixel circuits in advance during a dedicated reset period before the actual display period. This preliminary action equalizes the initial voltage states of capacitors in pixel circuits, ensuring uniform luminance characteristics in the low tone region without affecting the subsequent current-driven display operation.
2Reliability
If the reset voltage is increased to improve resetting effectiveness, then capacitor reset is improved, but luminance unevenness in border areas between drive circuit ICs increases
Solution Approach 1:
The patent establishes equipotential conditions by generating a common reset voltage that is distributed uniformly across all pixel circuits driven by different drive circuit ICs. The reset voltage generator produces a standardized voltage level that equalizes the electrical potential state of capacitors throughout the display panel, eliminating potential differences at border areas between adjacent drive circuit ICs.
Solution Approach 2:
The patent changes the reset voltage parameter to an optimized constant value that balances reset effectiveness with luminance uniformity. By carefully selecting and maintaining a specific reset voltage level, the system achieves sufficient capacitor discharge while avoiding excessive voltage differences that would cause luminance unevenness in border regions.
3Use of energy by moving object
If the drive current is reduced for low tone regions, then power consumption is reduced, but luminance unevenness becomes more conspicuous
Solution Approach 1:
The reset voltage is applied in advance during the reset period to pre-charge or pre-discharge capacitors to uniform initial states. This preliminary voltage equalization ensures that when low drive currents are subsequently applied in the display period, all pixel circuits start from the same electrical baseline, preventing luminance unevenness even at low current levels.
Solution Approach 2:
The system uses timing control signals that coordinate the reset operation across all pixel circuits simultaneously. The reset control mechanism ensures that capacitors are reset to uniform states before low tone display, creating a feedback loop where the reset state directly influences the uniformity of subsequent low-current drive operation.
Data Source
AI summary
An organic EL drive circuit includes a reset voltage generator circuit for generating a predetermined constant voltage for constant voltage resetting, reset switches provided between an output of the reset voltage generator circuit and terminal pins of an organic EL display panel and ON/OFF controlled by one of the timing control signal, a reset control signal similar to the timing control signal, a reset pulse, other pulse generated in the reset period in synchronism with these signal, and the pulse and an output terminal for outputting the predetermined constant voltage to other organic EL drive circuits, which have identical circuit constructions to that of the organic EL drive circuit and arranged adjacently to the organic EL drive circuit, as a voltage for constant voltage resetting.