Electroluminescence Pixel Circuit With Clamped Level Shifting
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Solution Overview
Problem
Existing pixel circuits for electroluminescence displays require transistors with high withstand voltages to handle operation voltage drops above 3V, leading to increased circuit size and reduced space efficiency.
Innovation Solution
A pixel circuit design incorporating a level shift transistor, bias transistor, and display transistor, configured to limit operation voltage drops within a clamping level, allowing the use of transistors with lower withstand voltages, thereby reducing the circuit area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transistors with high withstand voltages are used to handle operation voltage drops above 3V, then the pixel circuit can maintain proper voltage levels, but the transistor size increases and circuit area expands
Solution Approach 1:
The pixel circuit is divided into multiple functional blocks: a first circuit block containing a level shift transistor and first storage capacitor for voltage level shifting, and a second circuit block containing a driving transistor and second storage capacitor for current control. This segmentation allows each transistor to be optimized for its specific voltage requirements rather than requiring all transistors to handle the full voltage range.
Solution Approach 2:
A level shift transistor is introduced as an intermediary component between the voltage supply and the light-emitting device. This level shift transistor specifically handles the voltage level shifting function, allowing the driving transistor to operate at lower voltage levels and thus reducing its size while maintaining proper voltage levels at the light-emitting device.
2Stability of the object's composition
If transistors with high withstand voltages are used, then voltage control stability is maintained, but the resolution per unit area decreases
Solution Approach 1:
The circuit is segmented into voltage control functions and current control functions. The first circuit block handles voltage stabilization through the level shift transistor and first storage capacitor, while the second circuit block handles precise current control through the driving transistor and second storage capacitor. This segmentation allows optimized sizing for each function.
Solution Approach 2:
The invention changes the operating voltage parameter of the driving transistor by introducing a level shift mechanism. The driving transistor operates at a lower voltage level than the light-emitting device voltage, allowing for smaller transistor dimensions while maintaining stable voltage control through the level shift transistor and storage capacitors.
3Ease of operation
If the pixel circuit is designed to handle high voltage drops, then proper current control is achieved, but the circuit occupies more space
Solution Approach 1:
The pixel circuit is segmented into two functional blocks: the first block handles voltage level shifting and stabilization, while the second block handles current control. This segmentation allows the current control transistor to be smaller since it only needs to handle the voltage differential within its block rather than the full voltage range.
Solution Approach 2:
The level shift transistor acts as an intermediary that converts high voltage signals to lower voltage levels suitable for the driving transistor. This mediation allows proper current control to be achieved with smaller transistors that operate at lower voltage levels.
Data Source
AI summary
A pixel circuit of an electroluminescence display, comprising a level shift transistor coupled between a corresponding light emitting device and a level shift terminal, configured to limit an operation voltage drop between a level shift terminal and a first voltage line based on an enabling light emitting signal, ensuring that the operation voltage drop does not exceed a clamping level; a bias transistor, configured to operate based on a bias signal to provide a luminance current; and a display transistor, connected in series with the bias transistor between the level shift terminal and the first voltage line, configured to operate based on a display signal to modulate the luminance current to a display current providing to the corresponding light emitting device; wherein the light emitting device is coupled between the level shift transistor and the second voltage line, and the first voltage line is different from the second voltage line.