OLED Pixel Circuit for Low-Frequency 3D Display Driving
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Solution Overview
Problem
Existing organic light emitting displays face challenges in efficiently driving pixels at low frequencies, particularly for 3D imaging, which increases power consumption and reduces stability, and the degradation of organic light emitting diodes affects luminance.
Innovation Solution
The proposed solution involves a pixel circuit with specific transistor and capacitor configurations that allow for concurrent charging and emission of data signals, initializing the driving transistor in an on-bias state and using photodiodes to compensate for diode degradation, enabling low-frequency operation while maintaining image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If organic light emitting displays are driven at low frequency for 3D imaging, then power consumption is reduced and lifespan is extended, but display stability deteriorates and image quality decreases
Solution Approach 1:
The pixel circuit performs preliminary actions by initializing the driving transistor in an on-bias state before data signal input, and by concurrently charging the capacitor and emitting light during the emission period. This preliminary preparation ensures stable display performance even at low driving frequencies, preventing instability without requiring high-frequency operation
Solution Approach 2:
The invention maintains continuous useful action by having the capacitor charged and the organic light emitting diode emit light concurrently during the emission period. This continuous operation during emission ensures stable luminance output at low driving frequencies, preventing display instability while reducing power consumption compared to high-frequency operation
2Duration of action of stationary object
If organic light emitting diodes operate over time, then luminance output maintains initial brightness, but degradation occurs and luminance decreases
Solution Approach 1:
The pixel circuit incorporates feedback mechanisms through the driving transistor and capacitor configuration that automatically compensate for organic light emitting diode degradation. The circuit monitors and adjusts the voltage applied to the diode over time, maintaining consistent luminance output despite aging effects, thereby extending effective lifespan without sacrificing brightness
Solution Approach 2:
The invention utilizes parameter changes by dynamically adjusting the voltage applied to the organic light emitting diode through the driving transistor. As the diode degrades, the circuit modifies operational parameters to compensate, maintaining luminance consistency over extended periods and effectively extending the display's usable lifespan
3Speed
If pixel circuits are configured for concurrent charging and emission, then low-frequency operation is enabled, but circuit complexity increases
Solution Approach 1:
The pixel circuit merges the charging function and light emission function into a single concurrent operation during the emission period. By combining these two functions that traditionally occur at different times, the circuit enables low-frequency operation without requiring separate time slots, thus reducing the need for complex timing control mechanisms
Solution Approach 2:
The driving transistor and capacitor serve multiple functions simultaneously: the capacitor charges during emission rather than during a separate non-emission period, and the driving transistor controls both the charging process and the light emission. This multi-functionality reduces circuit complexity by eliminating the need for separate dedicated components for each function
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 approach allows for the implementation of 3D images at a lower driving frequency, reducing power consumption and extending the lifespan of organic light emitting diodes by compensating for degradation, thus improving display stability and cost-effectiveness.
Implementation Method 1
An organic light emitting display displays images using organic light emitting diodes that emit light through recombination of electrons and holes
Implementation Method 2
using photodiodes to compensate for diode degradation
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A pixel (142) includes an organic light emitting diode (OLED), a first driver (146) and a second driver (148). The second driver (148) controls an amount of current supplied from a first power source (ELVDD) to the organic light emitting diode (OLED), corresponding to a previous data signal. The first driver (146) stores a current data signal supplied from a data line (Dm) and supplies the previous data signal to the second driver (148). In the pixel (142), the second driver (148) includes a sixth transistor (M6) coupled between an initialization power source (Vinit) and a first node (N1) coupled to a gate electrode of a first transistor (M1), the sixth transistor (M6) being configured to turn on when a first control signal is supplied to a first control line (CI1); and a seventh transistor (M7) coupled between the first power source (ELVDD) and a second node (N2) commonly coupled to the first and second drivers (146, 148), the seventh transistor (M7) being configured to turn on when the first control signal is supplied.