OLED Pixel Circuit Leakage Compensation via Emission Bias Transistor
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Solution Overview
Problem
Organic light emitting diode (OLED) display devices experience image quality deterioration due to leakage currents during low-frequency driving, leading to current imbalances and reduced driving currents.
Innovation Solution
Incorporating an eighth transistor that controls current flow through third and fourth transistors in response to an emission bias signal, which compensates for voltage distortions caused by leakage currents, thereby reducing current imbalances and increasing driving currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If low-frequency driving is used to reduce power consumption, then power consumption is reduced, but leakage currents cause voltage distortion and image quality deterioration
Solution Approach 1:
The patent applies preliminary anti-action by introducing an eighth transistor that preemptively compensates for leakage current effects before they cause significant voltage distortion. The eighth transistor is configured to counterbalance the leakage currents of the third and fourth transistors, preventing voltage distortion at the first node that would otherwise occur during low-frequency driving periods when the display shows still images.
Solution Approach 2:
The patent implements feedback through the eighth transistor that monitors and compensates for voltage distortion caused by leakage currents. The eighth transistor receives control signals based on the emission bias signal and adjusts its conduction state accordingly, creating a feedback loop that maintains voltage stability at the first node despite ongoing leakage currents during low-frequency operation.
2Use of energy by moving object
If low-frequency driving is used to reduce power consumption, then power consumption is reduced, but current imbalances increase and driving currents decrease
Solution Approach 1:
The eighth transistor is designed to preemptively counterbalance leakage currents before they cause significant current imbalance. By being configured to conduct in opposition to the leakage currents of the third and fourth transistors, it maintains balanced current distribution to the OLED, ensuring adequate driving current even during extended low-frequency driving periods.
Solution Approach 2:
The feedback mechanism through the eighth transistor continuously adjusts current distribution based on leakage current effects. The emission bias signal controls the eighth transistor's conduction state, creating a dynamic feedback system that maintains proper current balance and driving current levels during low-frequency operation.
Data Source
AI summary
A pixel includes a first capacitor connected between a first electrode and a second electrode connected to a first node, a first transistor including a gate electrode connected to the first node, a first electrode connected to a second node, and a second electrode connected to a third node, a second transistor including a gate electrode that receives a data write gate signal, a first electrode that receives a data voltage, and a second electrode connected to the second node, a third transistor connected between the first node and the third node, a fourth transistor connected between the first node and an initialization voltage input terminal to which an initialization voltage is applied, an eighth transistor t connected to the third transistor and the fourth transistor, and an organic light emitting diode including an anode and a cathode receiving a second power supply voltage.