Pixel Circuit Auxiliary Transistor Leakage Compensation
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Solution Overview
Problem
Organic light emitting display devices face issues with maintaining desired luminance due to leakage currents generated when the second driving power supply is set low or when the devices are driven at low frequencies, leading to inconsistent voltage during a single frame.
Innovation Solution
Incorporating a pixel design with an organic light emitting diode, a first transistor, a storage capacitor, a second transistor, and an auxiliary transistor, where the second and auxiliary transistors have an overlapping turn-on period, and the auxiliary transistor is turned off before the second transistor, minimizing leakage currents through the use of oxide semiconductor and polysilicon semiconductor transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If the second driving power supply is set to be low or the device is driven at low frequency, then power consumption is reduced, but leakage current is generated from the gate electrode of the driving transistor causing voltage to not be maintained
Solution Approach 1:
The pixel circuit is divided into multiple transistor components (first transistor, second transistor, auxiliary transistor) with distinct functions. The auxiliary transistor specifically addresses leakage current issues while the first transistor controls current flow, allowing the system to maintain reliability at low power settings through specialized sub-components rather than a single general-purpose transistor.
Solution Approach 2:
The auxiliary transistor acts as an intermediary element between the data line and the driving transistor gate. It controls the charging and discharging of the storage capacitor to compensate for leakage currents, serving as a mediator that maintains voltage stability without requiring higher power supply levels or driving frequencies.
2Device complexity
If a single transistor is used to control current flow, then device complexity is reduced, but leakage current cannot be minimized affecting image quality
Solution Approach 1:
The single transistor control function is segmented into multiple specialized transistors: the first transistor for primary current control, the second transistor for data signal transmission, and the auxiliary transistor for leakage compensation. This segmentation allows each component to be optimized for its specific function, minimizing overall leakage current while maintaining manageable complexity through clear functional division.
Solution Approach 2:
Different transistor types are used in different locations within the pixel circuit based on local requirements. The auxiliary transistor is specifically positioned to address leakage current issues at the gate electrode, while other transistors handle data transmission and current control. This local optimization allows targeted solutions for leakage without redesigning the entire 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
This configuration ensures stable voltage at the gate electrode of the driving transistor, preventing image quality deterioration and allowing for the display of images with desired luminance by minimizing leakage currents.
Implementation Method 1
displays an image by using an organic light emitting diode that emits light by recombining an electron with a hole
Implementation Method 2
a storage capacitor connected between the first node and the first driving power supply
Data Source
AI summary
The present disclosure relates to a pixel displaying an image. A pixel includes an organic light emitting diode, a first transistor controlling an amount of current flowing from a first driving power supply to a second driving power supply via the organic light emitting diode in response to a voltage of a first node; a storage capacitor connected between the first node and the first driving power supply; a second transistor connected between a data line and the first node and turned on when a scan signal is supplied to a first scan line, and an auxiliary transistor connected between the second transistor and the data line and turned on when a scan signal is supplied to a second scan line. The second transistor and the auxiliary transistor have an overlapping turn-on period, and the second transistor is turned off before the auxiliary transistor is turned off.