Display Device Charge Removal Circuit for Transistor Degradation
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Solution Overview
Problem
In active matrix display devices using organic electroluminescence, the continuous holding of electric charges in the gate of driving transistors during power supply cessation leads to degradation, affecting the reliability and characteristics of the transistors and ultimately the display device's long-term reliability.
Innovation Solution
A display device configuration that includes a light emitting element, a transistor, and an electric charge drawing unit connected to the transistor's gate, which draws electric charges when the power supply is stopped, using switches and a detection unit to manage the power supply voltage and switch states for effective charge removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a transistor is provided to electrically connect the gate and source of a driving transistor when power supply is stopped, then the structure is simplified, but electric charges are not sufficiently removed from the gate, causing degradation in transistor reliability and characteristics
Solution Approach 1:
The patent divides the charge removal function into multiple transistors (first transistor and second transistor) rather than using a single transistor. The first transistor removes charges from the gate, while the second transistor removes charges from the source, enabling more complete charge removal and preventing transistor degradation without excessive structural complexity
Solution Approach 2:
The patent introduces a third transistor as an intermediary element to control the connection between the source and the charge removal path. This third transistor acts as a mediator that coordinates the operation of the first and second transistors, ensuring proper charge removal sequence and preventing residual charges that would degrade transistor reliability
2Stability of the object's composition
If electric charges are continuously held in the gate of the driving transistor during power supply cessation, then the transistor maintains its operational state, but the transistor degrades due to electrical stress, affecting long-term reliability
Solution Approach 1:
The patent performs charge removal actions before the transistor degradation can occur during power supply cessation. By detecting the power supply stop condition and immediately activating the charge removal transistors, the system preemptively removes harmful charges from the gate and source, preventing electrical stress accumulation that would otherwise degrade transistor reliability over time
Solution Approach 2:
The patent converts the harmful effect of held electric charges into a beneficial charge removal mechanism. By detecting when charges accumulate to harmful levels during power supply cessation, the system activates specific transistors to drain these charges through controlled paths, transforming the potential degradation source into a protective charge management feature that enhances long-term reliability
Data Source
AI summary
A display device according to the present disclosure is a display device including a plurality of pixels arranged in a matrix, each of the plurality of pixels including: an EL element that emits light according to the amount of current supplied; a driving transistor that controls light emission of the EL element; and switches connected to a gate of the driving transistor. The display device includes an electric charge drawing unit configured to draw electric charges in the gate of the transistor provided in each of the plurality of pixels when power supply to the display device is stopped.