Pixel Circuit Memory Voltage Selection for AC Displays
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Solution Overview
Problem
The existing AC-driven display devices with pixel memory circuits face challenges in achieving high-resolution displays due to the large circuitry required for periodically inverting the voltage polarity, which is necessary for efficient power consumption and image retention.
Innovation Solution
The implementation of a pixel circuit configuration that includes a voltage selection circuit with two transistors, a first selection transistor, and a second selection transistor, which alternately selects voltages from two power source lines to apply to a pixel electrode without being affected by the threshold voltage, allowing for AC-driven operation without rewriting data in the pixel memory circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a pixel memory circuit with voltage selection circuit is added to enable AC-driven operation, then power consumption is reduced and image retention is improved, but the circuit scale becomes large and high-resolution display is not achieved
Solution Approach 1:
The patent combines the voltage selection circuit functionality with the existing pixel memory circuit by sharing transistor components. The first and second selection transistors are integrated into the pixel circuit structure, allowing the circuit to perform both data storage and voltage selection functions without adding separate dedicated components, thereby reducing overall circuit scale while enabling AC-driven operation
Solution Approach 2:
The pixel memory circuit is designed to serve multiple functions: it stores display data in the latch circuit and simultaneously functions as a voltage selection circuit that applies appropriate voltages to the pixel electrode based on stored data. This multi-functionality eliminates the need for separate voltage selection circuitry, reducing circuit complexity while maintaining AC-driven capability
2Manufacturing precision
If two transmission gates with P-channel and N-channel transistors are used for voltage selection, then voltage selection accuracy is improved, but the circuit complexity increases and more transistors are required per pixel
Solution Approach 1:
The patent extracts and eliminates the threshold voltage effect from the voltage selection process by using a specific circuit configuration where the selection transistors are connected in a manner that prevents threshold voltage drops from affecting the applied voltage. This allows accurate voltage selection without requiring the traditional two-transistor transmission gate structure
Solution Approach 2:
Instead of using the conventional approach of two transmission gates with P-channel and N-channel transistors controlled in mutually inverted manner, the patent inverts the control strategy by using a single selection transistor controlled by a selection signal that directly enables or disables voltage application to the pixel electrode, simplifying the circuit while maintaining voltage selection accuracy
Data Source
AI summary
When binary pixel data is written to a pixel circuit, of an H-level (3V) and a L-level (0V), a voltage of the level indicating the binary pixel data is held at a first node, and a voltage of the inverted level thereof is held at a second node. The first and second nodes are connected to a third node via N-channel transistors, respectively, and first and second selection control signals are supplied to gate terminals of the transistors, respectively. Voltage levels of the first and second selection control signals are periodically switched between 5V indicating the H-level and 0V indicating the L-level in a mutually inverted manner. As a result, the voltage of the first node and the voltage of the second node are alternately selected and applied to a pixel electrode of a display element.