Display Inverter Circuit for Stable OLED Pixel Luminance
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Solution Overview
Problem
In active matrix organic EL displays, variations in threshold voltage and mobility across pixels lead to non-uniform luminance due to increased power consumption and peak voltage variations in existing inverter circuits, affecting threshold and mobility corrections.
Innovation Solution
The proposed inverter circuit includes five transistors and two capacity elements, with specific transistor configurations and control signals to manage voltage transitions and reduce power consumption by eliminating simultaneous on-states of certain transistors, thereby stabilizing output voltage and reducing luminance variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional inverter circuit with two transistors is used, then the circuit complexity is low, but power consumption increases and output voltage peak variations occur
Solution Approach 1:
The inverter circuit is segmented into five transistors (Tr1-Tr5) with distinct functional roles: Tr1 and Tr3 control gate voltages, Tr2 controls output voltage, Tr4 controls capacity element connection to gate, and Tr5 controls capacity element connection to voltage line. This segmentation allows independent optimization of each transistor's operation to eliminate simultaneous conduction and reduce power consumption.
Solution Approach 2:
The circuit employs dynamic control of transistor switching states through capacity elements (C1, C2) that store and release charge to sequentially activate transistors. The capacity elements create time-delayed switching sequences that ensure Tr1-Tr5 never conduct simultaneously, dynamically adapting the conduction path based on operational phase.
2Device complexity
If a conventional inverter circuit is used, then the circuit configuration is simple, but output voltage peak variations affect threshold and mobility corrections
Solution Approach 1:
The circuit incorporates capacity elements C1 and C2 that provide voltage feedback to the gates of Tr2, Tr4, and Tr5. These capacity elements store voltage information and release it in a controlled sequence, creating a feedback mechanism that stabilizes the output voltage peak by preventing premature or simultaneous transistor activation that would cause voltage variations.
3Loss of energy
If transistors are controlled to eliminate simultaneous on-states, then power consumption is reduced, but circuit complexity increases
Solution Approach 1:
Capacity elements C1 and C2 act as intermediary components between the transistors, mediating the switching sequences to prevent simultaneous conduction. These capacity elements store electrical charge and release it in a controlled manner, serving as buffers that coordinate the timing of transistor activation without requiring complex control logic.
Data Source
AI summary
An inverter circuit includes: a first transistor and a second transistor; a first switch and a second switch; and a first capacity element, in which the first and second transistors are connected in series between a first voltage line and a second voltage line, the first and second switches are connected in series between a supply voltage line and a gate of the second transistor, and are alternately turned on and off so as not to be turned on simultaneously, an end of the first capacity element is connected between the first switch and the second switch, and off-state of the first transistor allows a predetermined fixed voltage to be supplied from the supply voltage line to the gate of the second transistor through the first switch, the end of the first capacity element and the second switch.