LTPS Pixel Circuit for Low-Gray Discharge Current Matching
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Solution Overview
Problem
In displays using the LTPS process, the discharging current does not match the corresponding components in the driving transistor, affecting low gray drive uniformity and display quality.
Innovation Solution
A pixel circuit design that includes a discharging circuit, compensation control circuit, light-emitting control circuit, and driving circuit, which controls the connection and disconnection of nodes to match the discharging current with the driving transistor, using a threshold voltage compensation mechanism to offset uncontrolled leakage and ensure accurate driving current during low grayscale displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a small current bypass discharging channel is formed using LTPS process, then the discharging current is generated, but the discharging current does not match the driving transistor components, causing poor low gray drive uniformity
Solution Approach 1:
The patent introduces a compensation control circuit that dynamically adjusts the discharging current parameters to match the driving transistor characteristics. By changing the electrical parameters (current magnitude, timing) of the discharging channel based on detected threshold voltage variations, the system achieves uniform low gray drive performance across different pixels and process variations.
Solution Approach 2:
The patent implements a feedback mechanism where the compensation control circuit monitors the driving transistor's threshold voltage and adjusts the discharging current accordingly. This closed-loop control ensures that the discharging current matches the driving transistor components, resolving the mismatch problem that causes poor low gray uniformity.
2Ease of operation
If the discharging current terminal is directly connected to the first electrode of the light-emitting element, then the discharging current flows directly, but uncontrolled leakage affects the driving current accuracy
Solution Approach 1:
The patent introduces a compensation control circuit as an intermediary between the discharging current terminal and the light-emitting element. This intermediate circuit selectively controls the connection, allowing discharging current to flow when needed while preventing uncontrolled leakage during driving phases, thereby maintaining driving current accuracy.
Solution Approach 2:
The patent makes the connection between the discharging current terminal and the light-emitting element dynamic rather than static. The compensation control circuit adjusts the connectivity in real-time based on the operational phase (compensation vs. light-emitting), enabling the system to optimize both discharging current flow and driving current accuracy at different times.
3Reliability
If multiple control circuits are added to control node connections, then current matching and leakage control are improved, but the circuit complexity increases
Solution Approach 1:
The compensation control circuit is designed to perform multiple functions: controlling the discharging current magnitude, managing node connections, preventing leakage, and compensating for threshold voltage variations. By making this single circuit multi-functional, the patent achieves current matching and leakage control without proportionally increasing overall circuit complexity.
Solution Approach 2:
The patent combines multiple control functions (discharging control, connection management, leakage prevention) into a single integrated compensation control circuit. This merging of functions reduces the number of separate components needed, thereby limiting the increase in device complexity while achieving the desired current matching and control.
Data Source
AI summary
A pixel circuit, a pixel driving method, and a display device. The pixel circuit includes a light-emitting element, a driving circuit, a compensation control circuit, a light-emitting control circuit and a discharging circuit; the compensation control circuit controls connection or disconnection between the first node and the driving node under the control of the compensation control signal; the light-emitting control circuit controls connection or disconnection between the driving node and the first electrode of the light-emitting element under control of the light-emitting control signal; the discharging circuit is used for generating a discharging current; in a compensation phase, the discharging current terminal is connected to the driving node, and in a light-emitting phase, the discharging current terminal is connected to the driving node and the first electrode of the light-emitting element, and the discharging current terminal is not directly electrically connected to the first electrode of the light-emitting element.