Pixel Cell Driving Circuit Stabilizes Storage Capacitor Voltage
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Solution Overview
Problem
The existing OLED display panels, particularly passive-matrix OLEDs, suffer from flicker due to electrical charge leakage in the storage capacitor, leading to unstable voltage and reduced display quality, which is not suitable for high-resolution and large-sized displays.
Innovation Solution
A pixel cell driving circuit is introduced that includes a third thin film transistor to charge the storage capacitor when the switch thin film transistor is turned off, using a charging signal provided through a dedicated charging line, synchronizing signals to maintain stable voltage and prevent flicker.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a switch thin film transistor is used to control the storage capacitor charging, then the pixel cell can be controlled to emit light within a controllable frame time, but electrical charge leakage occurs when the transistor is turned off, causing storage capacitor voltage to drop and resulting in display flicker
Solution Approach 1:
The patent applies preliminary action by proactively charging the storage capacitor through a dedicated charging transistor during the frame period when the switch transistor is off. Instead of waiting for voltage drop to occur and then correcting it, the system pre-charges the capacitor to compensate for anticipated leakage, ensuring voltage remains stable throughout the display frame cycle.
Solution Approach 2:
The patent implements feedback by using the known leakage characteristics of the switch transistor to determine the appropriate charging current and timing. The charging transistor is controlled based on the frame timing signal, creating a feedback loop where the system adjusts charging behavior to counteract the predictable voltage drop caused by leakage, thereby maintaining stable capacitor voltage.
2Ease of operation
If the switch thin film transistor is turned off to maintain pixel state, then light emission can be controlled, but leakage current causes voltage drop and display flicker
Solution Approach 1:
The patent extracts the harmful leakage current effect by separating the charging function from the switching function. Instead of relying solely on the switch transistor to maintain voltage, a dedicated charging transistor is introduced to specifically address the leakage issue. This extraction allows the switch transistor to focus on control while the charging transistor compensates for leakage independently.
Solution Approach 2:
The charging transistor acts as an intermediary element between the power supply and the storage capacitor. It mediates the voltage maintenance function by providing compensatory charging current that counteracts the leakage current from the switch transistor, thereby eliminating the harmful effect without interfering with the primary control function of the switch transistor.
3Use of energy by stationary object
If active-matrix driving circuit is implemented with TFT and storage capacitor, then OLED can emit light controllably with low power consumption, but additional components increase device complexity
Solution Approach 1:
The charging transistor is designed to work within the existing active-matrix pixel cell framework, sharing the same timing and control infrastructure. It operates during the same frame period and uses the same power supply connections, thereby providing additional voltage stabilization functionality without requiring completely separate control circuits or additional power management components.
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 effectively stabilizes the storage capacitor voltage, preventing flicker and enhancing display quality by ensuring continuous light emission in OLEDs, meeting the requirements for high-resolution and large-sized displays.
Implementation Method 1
the storage capacitor Cs is charged through the switch thin film transistor T1... the storage capacitor Cs leaks to the data line along the switch transistor T1 when the switch transistor T1 is at the turn-off state
Implementation Method 2
the drive thin film transistor T2 is turned on to drive the OLED to emit light... the switch thin film transistor T1 enters a turn-on state... voltage difference between the source s1 and the drain d1 of the switch thin film transistor T1 decrease to a small value
Implementation Method 3
the OLED display panel has the characteristics of simple preparation process, low cost, low power consumption, high lighting brightness... the drive thin film transistor T2 is turned on to drive the OLED to emit light
Data Source
AI summary
A pixel cell driving circuit driving an organic electric lighting component comprises a first, a second and a third thin film transistors and a storage capacitor. The first thin film transistor is turned on or turned off under a control of a first scanning signal. When the first thin film transistor is turned on, the storage capacitor is charged by a data signal. The second thin film transistor is turned on under an action of the storage capacitor and drives an OLED. The third thin film transistor is turned on under a control of the second scanning signal when the first thin film transistor is turned off, and the storage capacitor is charged by a charging signal. The pixel cell driving circuit may effectively avoid the flicker due to the electrical charge leakage of the storage capacitor. The disclosure further provides a pixel cell and a pixel cell driving method.