Gate Driver Emission Switching Transistor for OLED Current Leakage
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Solution Overview
Problem
In organic light emitting diode (OLED) display devices, current leakage and unintended current paths can occur when power is applied, leading to measurement errors and screen flickers due to the interaction between the driving transistor and the OLED, affecting image quality and device performance.
Innovation Solution
The implementation of a gate driver and OLED display device configuration that includes a driving transistor, an emission switching transistor, and a timing controller to maintain the emission switching transistor in an off state until the internal pixel terminal is stabilized, preventing the driving transistor from affecting the OLED during power application and impedance measurement, and using a level shifter and scan drivers to control current flow and voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the driving transistor is connected to the organic light emitting diode to supply operating current, then the OLED can be driven to emit light, but current leakage and unintended current paths occur when power is applied, causing measurement errors and screen flickers
Solution Approach 1:
An emission switching transistor is introduced as an intermediary component between the driving transistor and the OLED. This switching transistor acts as a mediator that controls the timing of current flow to the OLED, preventing current leakage during power application and impedance measurement while enabling normal operation during display periods
Solution Approach 2:
The emission switching transistor is turned off during power application and impedance measurement phases before the OLED is ready to receive current. This preliminary action of blocking the current path in advance prevents unintended current flow and measurement errors, and only after the internal pixel terminal is stabilized does the switching transistor turn on to allow normal operation
2Measurement precision
If impedance measurement is performed on the organic light emitting diode to compensate for threshold voltage, then threshold voltage compensation can be achieved, but current leakage in regions other than the sensing path causes measurement errors
Solution Approach 1:
The emission switching transistor serves as a precise mediator that isolates the OLED from the driving transistor during impedance measurement. This ensures that current flows only through the intended sensing path and not through other regions, eliminating measurement errors caused by leakage
Solution Approach 2:
The emission switching transistor is kept in the off state during impedance measurement to preemptively prevent current leakage in non-sensing regions. This preliminary blocking action counteracts the potential harmful effect of current diversion before it can occur, ensuring accurate measurement
3Productivity
If power is applied to the organic light emitting diode display device, then the device can operate and display images, but unintended current paths form causing screen flickers and image quality issues
Solution Approach 1:
The emission switching transistor is activated in advance to block current flow during the power application phase before the OLED is stabilized. This preliminary protective action prevents the formation of unintended current paths that would cause screen flickers, and only after stabilization does normal display operation begin
Solution Approach 2:
The emission switching transistor acts as a protective intermediary that separates the power application phase from the display operation phase. During power application, it blocks current to prevent harmful effects, and during display operation, it enables controlled current flow for normal image display
Data Source
AI summary
A gate driver, an organic light emitting diode display device and a method of driving the same, which are capable of preventing a driving transistor from affecting a light emitting diode when power is applied and when impedance is measured, are discussed. The organic light emitting diode display device can include a driving transistor connected to one end of an organic light emitting diode to supply operating current to the organic light emitting diode, an emission switching transistor switched according to an emission control signal to control flow of current supplied from the driving transistor to the organic light emitting diode, and a timing controller configured to perform control to maintain the emission switching transistor in an off state such that the driving transistor does not affect the organic light emitting diode until an internal terminal of a pixel of a display panel is stabilized when power is applied.