Organic EL Driving Circuit Capacitance Reset for Threshold Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing display devices with organic electroluminescent (EL) technology face challenges in suppressing time-varying fluctuations in transistor threshold voltage due to variations in electrical characteristics and parasitic capacitance, leading to inconsistent brightness control and display quality.
Innovation Solution
A method for driving organic EL display devices that includes a storage capacitor connected between the gate and source or drain of the driving transistor, with a reverse bias voltage applied between the gate and source, and a capacitance reset step performed before reverse-bias application to stabilize the source potential and ensure precise voltage application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a reverse bias voltage is applied to suppress threshold voltage fluctuations, then threshold voltage stability is improved, but brightness control precision deteriorates due to inability to apply proper reverse bias voltage
Solution Approach 1:
The patent applies a reset voltage before applying the reverse bias voltage to clear the charge of the storage capacitor. This preliminary action ensures that the reverse bias voltage is applied accurately without being affected by residual charge, thereby resolving the contradiction between threshold voltage stability and brightness control precision
Solution Approach 2:
The patent introduces a reset voltage as an intermediary step between the light emission period and the reverse bias application. This intermediary voltage serves to clear the storage capacitor charge, enabling the subsequent reverse bias voltage to be applied precisely and effectively suppress threshold voltage fluctuations without affecting brightness control
2Stability of the object's composition
If reverse bias voltage is applied during non-light emission period, then threshold voltage fluctuations are suppressed, but display quality deteriorates due to improper reverse bias voltage application
Solution Approach 1:
The reset voltage is applied before the reverse bias voltage during the non-light emission period to ensure proper charge clearing. This preliminary action enables the reverse bias voltage to be applied correctly, suppressing threshold voltage fluctuations while maintaining display quality
Solution Approach 2:
The patent uses the non-light emission period as a feedback opportunity to reset the storage capacitor and apply reverse bias voltage. This timing ensures that the transistor threshold voltage is stabilized without affecting the light emission quality, as the reset and reverse bias application occur when the pixel is not being displayed
Data Source
AI summary
A method for driving a display device including a plurality of pixels arranged in rows and columns, each of the pixels including an organic EL device that emits light in accordance with supplied current, a driving transistor that supplies current to the organic EL device, and a storage capacitor connected between the gate of driving transistor and a source or drain thereof, includes causing the organic EL device to emit light by supplying current to the organic EL device; resetting charge of at least one of the storage capacitor and a parasitic capacitance of the organic EL device; and applying a reverse bias voltage between the gate and source of the driving transistor. The resetting is performed between the light emission and the reverse-bias application.