Display Pixel Circuit With Initialization and Threshold-Voltage Compensation
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Solution Overview
Problem
Leakage currents in pixel driving circuits of display devices lead to fluctuations in current flow through light emitting elements, degrading display quality.
Innovation Solution
A pixel structure with a 6T2C configuration, including specific transistors and capacitors, is employed to stabilize current flow by using compensation and initialization signals, reducing the impact of transistor threshold voltage and power source variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pixel driving circuit is used, then the device complexity is low, but leakage current causes fluctuation in current flow through light emitting elements degrading display quality
Solution Approach 1:
The pixel circuit performs preliminary actions by applying an initialization scan signal to initialize the first node to a reference voltage before the light emitting element is activated. This preliminary initialization prevents leakage current from affecting the display quality, as the node is pre-set to a known stable state.
Solution Approach 2:
The pixel circuit implements feedback by using a compensation scan signal that monitors and compensates for threshold voltage variations in the first transistor. The compensation mechanism adjusts the gate voltage of the first transistor based on detected variations, maintaining stable current flow through the light emitting element despite manufacturing tolerances or temperature changes.
2Manufacturing precision
If transistor threshold voltage and power source variations occur, then manufacturing precision is affected, but display quality degrades due to current fluctuation
Solution Approach 1:
The pixel circuit applies parameter changes by dynamically adjusting the gate voltage of the first transistor through the compensation scan signal. This adjustment compensates for threshold voltage variations and power source fluctuations, maintaining consistent current flow and luminance output despite manufacturing precision variations or environmental changes.
Solution Approach 2:
The compensation scan signal acts as an intermediary mechanism between the fixed reference voltage and the variable threshold voltage conditions. It mediates the effect of manufacturing variations by introducing an adjustable control parameter that balances out the inconsistencies, ensuring stable display performance.
3Reliability
If leakage current occurs in the pixel driving circuit, then the current flow through the light emitting element changes, but display quality deteriorates
Solution Approach 1:
The pixel circuit applies preliminary anti-action by initializing the first node to a reference voltage through the initialization scan signal before any leakage current can affect the display. This pre-established reference state creates a counterbalancing effect that prevents leakage current from causing luminance fluctuations, as the node is already held at a stable potential.
Solution Approach 2:
The compensation scan signal provides feedback that actively counteracts leakage current effects. By monitoring the actual voltage at the first node and comparing it with the reference voltage, the feedback mechanism adjusts the gate voltage of the first transistor to compensate for any current leakage, maintaining stable luminance output.
Data Source
AI summary
A pixel includes a light emitting element connected between a first power source line, through which a first power source is provided, and a first node, a first transistor including a first electrode electrically connected to the first node, a second electrode electrically connected to a second node, and a gate electrode electrically connected to a third node, a second transistor including a first electrode electrically connected to a data line through which a data signal is provided, a second electrode electrically connected to the third node, and a gate electrode for receiving a scan signal, a third transistor, a fourth transistor, and a first capacitor connected between the second node and the third node.