Display Device Floating State Power Reduction
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Solution Overview
Problem
Conventional active matrix display devices have high off-state current, leading to signal leakage and increased power consumption, as signals need to be frequently rewritten for the same image, making it difficult to reduce power consumption.
Innovation Solution
A method for driving a display device that allows it to remain in an off state with a still image displayed by holding the voltage applied to the display element in a floating state, reducing power consumption and enabling the device to be put into a low-power, secure state with a desired image displayed, using a transistor with low off-state current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If power supply is stopped to reduce power consumption, then power consumption is reduced, but the displayed image may be lost or compromised
Solution Approach 1:
The capacitor is charged to the desired voltage level before power supply is stopped, so that the image can be maintained without further power supply. This preliminary charging action ensures that when power is cut off, the capacitor has sufficient energy stored to maintain the display state, thus reducing power consumption while preserving image reliability.
Solution Approach 2:
The capacitor copies or replicates the function of continuous power supply by storing electrical energy and releasing it to maintain the voltage across the display element. Instead of relying on continuous external power, the capacitor creates a local energy reservoir that mimics the effect of ongoing power supply, enabling the display to maintain its state without active power input.
2Speed
If transistor off-state current is high, then the transistor can switch quickly, but signal leaks and power consumption increases
Solution Approach 1:
The capacitor acts as an intermediary element between the transistor and the display element. It decouples the transistor's switching function from the voltage maintenance function. The transistor quickly switches to charge or discharge the capacitor, and the capacitor then maintains the voltage smoothly, preventing signal leakage while preserving fast switching capability.
Solution Approach 2:
The invention changes the operational parameters by introducing a capacitor with specific capacitance value that determines the discharge time constant. By selecting appropriate capacitance, the system achieves fast switching response while maintaining voltage for sufficient display duration, thus optimizing both speed and energy efficiency by adjusting the electrical parameters of the circuit.
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
The method significantly reduces power consumption and enhances security by allowing the display device to maintain an image without further power supply, while maintaining image quality and convenience.
Implementation Method 1
a transistor formed using a metal oxide for a channel formation region is used as a switching element connected to each pixel electrode
Data Source
AI summary
An object is to provide a convenient display device which consumes sufficiently small amount of power and a method for driving such a display device. The display device can be in an off state with a still image displayed in a still image display mode in which a pixel electrode and a common electrode which are for applying a voltage to the display element are brought into a floating state so that a voltage applied to the display element is held, and a still image is displayed without further supply of a potential. The display device is put to an off state with a desired image displayed in the still image display mode, whereby the display device can have a higher level of security and can be more convenient.