Transistor Gate Voltage Control for Display Current Stability
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Solution Overview
Problem
Existing display devices face issues with current flow to display elements during signal writing operations, leading to display defects and increased power consumption due to the need for large transistors to manage high current levels, and variations in current characteristics between signal writing and light emission operations.
Innovation Solution
A semiconductor device structure incorporating a transistor, switches, and a capacitor is used to control current flow by adjusting the gate-source voltage, preventing current from flowing to the load during signal writing and ensuring consistent current delivery during light emission, without varying power source line potentials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large current is supplied to the display element during signal writing operation, then the signal can be written quickly, but current flows to the display element causing display defects and increased power consumption
Solution Approach 1:
The patent applies dynamics by making the transistor operate in different regions (linear vs saturation) depending on the operation phase. During signal writing, the transistor is controlled to operate in the linear region allowing high current flow for fast writing. During light emission, it operates in the saturation region to provide stable current. This dynamic operation mode switching resolves the contradiction between fast writing and preventing harmful current flow.
Solution Approach 2:
The patent changes the operating parameters of the transistor by controlling the gate-source voltage to vary the drain-source voltage. By adjusting these voltage parameters, the transistor transitions between linear and saturation regions, enabling the system to achieve both fast signal writing and stable current control for light emission without display defects.
2Power
If a large transistor is used to manage high current levels, then sufficient current can be supplied to the display element, but the device size and power consumption increase
Solution Approach 1:
The patent uses dynamic operation of the transistor, switching between linear and saturation regions, to achieve high current capability without requiring an oversized transistor. The same transistor provides both high current during writing and stable current during emission by changing its operating region, reducing device size while maintaining power supply capability.
Solution Approach 2:
The transistor serves multiple functions: it acts as a current source during light emission and as a switch during signal writing. This multi-functionality allows a single transistor to handle both stable current supply and high-speed switching without requiring separate components, thereby reducing overall device complexity.
3Reliability
If the transistor operates in saturation region during signal writing, then stable current is maintained, but signal writing speed decreases
Solution Approach 1:
The patent dynamically switches the transistor operating region based on the operation phase. During signal writing, it operates in the linear region for fast response. During light emission, it transitions to the saturation region for stable current. This dynamic region switching resolves the contradiction between speed and stability.
4Manufacturing precision
If power source line potentials are varied per row, then current control is improved, but the circuit complexity and manufacturing difficulty increase
Solution Approach 1:
The patent extracts the current control function from the power source line potential variation and implements it within the pixel circuit itself through transistor operation mode control. Instead of varying potentials externally per row, the control is done locally by managing the transistor's operating region, simplifying the power source line configuration while maintaining precise current 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 solution prevents current flow to display elements during signal writing, reduces power consumption, and maintains consistent current values between signal writing and light emission operations, enhancing display performance and reducing defects.
Implementation Method 1
a capacitor, connected between the gate terminal and the first terminal of the transistor
Data Source
AI summary
In case the size of the transistor is enlarged, power consumption of the transistor is increased. Thus, the present invention provides a display device capable of preventing a current from flowing to a display element in signal writing operation without varying potentials of power source lines for supplying a current to the display element per row. In setting a gate-source voltage of a transistor by applying a predetermined current to the transistor, a potential of a gate terminal of the transistor is adjusted so as to prevent a current from flowing to a load connected to a source terminal of the transistor. Therefore, a potential of a wire connected to the gate terminal of the transistor is differentiated from a potential of a wire connected to a drain terminal of the transistor.