Light Emitting Device Driving Speed via Node Potential Control
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Solution Overview
Problem
Existing light emitting devices, particularly organic electroluminescence (EL) elements, face challenges in speeding up driving operations, leading to delayed light emission and reduced responsiveness to input signals, especially at low luminance levels, due to variations in threshold voltages among pixels and long charging times.
Innovation Solution
A light emitting device configuration that includes a driving transistor, a threshold correction unit, and an electric potential setting unit, which sets distinct electric potentials at a node between the driving transistor and the light emitting element, allowing for faster driving by reducing charging time and stabilizing threshold voltages, thereby improving responsiveness and image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional driving circuits are used for organic light emitting devices, then the device structure is simple, but the driving speed is slow and light emission response is delayed
Solution Approach 1:
The circuit is divided into multiple specialized transistors: a driving transistor for current control, a threshold correction transistor for voltage compensation, and an electric potential setting transistor for node potential control. This segmentation allows each component to perform a specific function efficiently, achieving fast driving speed while maintaining manageable circuit complexity through functional specialization.
Solution Approach 2:
The threshold correction transistor and electric potential setting transistor perform preliminary corrections before the main driving operation. The threshold correction unit compensates for transistor threshold variations in advance, and the electric potential setting unit pre-establishes appropriate node potentials, enabling the light emitting element to respond faster without waiting for gradual voltage stabilization.
2Loss of time
If conventional single electric potential is applied at the node, then the circuit is simple, but the charging time is long and responsiveness is poor
Solution Approach 1:
The electric potential at the node between the driving transistor and light emitting element is made dynamic rather than fixed. The electric potential setting transistor adjusts the node potential according to different operating conditions, allowing optimal charging speeds at different luminance levels and reducing overall charging time while managing circuit complexity through adaptive control.
Solution Approach 2:
The circuit changes the electric potential parameter at the node between the driving transistor and light emitting element. By adjusting this potential parameter, the charging speed of the light emitting element is controlled, enabling faster response times. The threshold correction unit simultaneously adjusts voltage parameters to compensate for transistor variations, achieving reduced charging time with acceptable circuit complexity.
3Productivity
If fast driving is implemented without threshold correction, then the driving speed increases, but the image quality deteriorates due to voltage variations
Solution Approach 1:
The threshold correction transistor creates a feedback mechanism that compensates for threshold voltage variations in the driving transistor. By sensing and correcting these variations in real-time, the circuit maintains consistent current control through the light emitting element, ensuring uniform image quality across all pixels even when operating at high driving speeds.
Solution Approach 2:
The threshold correction transistor acts as an intermediary between the signal line and the driving transistor. It mediates the voltage signal by compensating for threshold variations before the signal reaches the driving transistor, ensuring that the driving transistor receives a corrected voltage that accounts for its specific threshold characteristics, thereby maintaining image quality while enabling fast response.
Data Source
AI summary
A light emitting device includes a light emitting element, a driving transistor configured to control driving of the light emitting element, a threshold correction unit configured to perform compensation for a voltage corresponding to a threshold of the driving transistor, and an electric potential setting unit configured to set an electric potential of a node between the driving transistor and the light emitting element, wherein the electric potential setting unit sets a first electric potential and a second electric potential different from the first electric potential, at the node.