OLED Driving Circuit Source Potential Reset for Precise Light Emission Timing
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Solution Overview
Problem
Existing light emitting apparatuses, such as those using OLED devices, face challenges in accurately setting the time length for light emission, which affects the gradation of pixels recognized by observers, due to difficulties in precisely determining the source potential of the driving transistor and the current flowing through it.
Innovation Solution
A light emitting apparatus with a pixel circuit and drive circuit that includes a driving transistor, capacitive element, and switching devices, where the drive circuit sets the source potential to a reset value independently of the transistor's properties, allowing precise control of the light emission time and luminance by varying the data potential with a specific time change rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the source potential of the driving transistor is determined by compensation action reflecting transistor properties, then the driving current can be set independent of transistor properties, but the source potential value cannot be accurately grasped, making it difficult to precisely set the light emission time
Solution Approach 1:
The patent applies preliminary action by setting the source potential to a predetermined reset potential value before the light emission period begins. This reset potential is established in advance through a reset operation that sets the source potential to a known reference value, independent of transistor properties. By preparing the source potential in advance at a known value, the system can precisely control the light emission time without needing to accurately measure or know the actual source potential during operation.
2Manufacturing precision
If the time length from starting point until OLED starts emitting light cannot be precisely set, then the light emission duration cannot be accurately controlled, but increasing measurement precision requires complex circuitry to accurately determine source potential
Solution Approach 1:
The patent extracts the source potential control function from the complex measurement and control system. Instead of using complex circuitry to measure and determine the actual source potential value, the invention separates the source potential setting function by directly setting it to a predetermined reset potential value through a simple reset operation. This extraction simplifies the circuit by removing the need for complex measurement and determination mechanisms while maintaining precise timing control.
3Adaptability or versatility
If the source potential is set to reflect transistor properties through compensation, then mobility compensation is achieved, but the actual source potential value remains unknown and difficult to control for precise timing
Solution Approach 1:
The patent applies preliminary action by establishing the source potential at a predetermined reset potential value before the light emission period. This reset operation is performed in advance to set the source potential to a known reference value that is independent of transistor properties. By preparing the source potential in advance at a known value, the system achieves both adaptability to transistor variations and precise knowledge of the source potential value for accurate timing control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables highly precise setting of the time length for light emission and the corresponding luminance, allowing for accurate gradation of pixels recognized by observers, ensuring uniform and desired light emission across the display.
Implementation Method 1
a capacitive element arranged between a gate and a source of the driving transistor
Implementation Method 2
light emitting device such as an organic light emitting diode (hereinafter, referred to as "OLED") device including those called an organic EL (electroluminescent) device
Data Source
AI summary
A light emitting apparatus includes a pixel circuit, and a drive circuit which drives the pixel circuit. The pixel circuit has a light emitting device, a driving transistor connected in series to the light emitting device, a capacitive element arranged between a gate and a source of the driving transistor, a first switching device arranged between the gate of the driving transistor and a signal line corresponding to the pixel circuit, and a second switching device arranged between the source of the driving transistor and a reset line.