Pixel Driving Circuit Hysteresis Compensation Switch
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Solution Overview
Problem
Organic light emitting diode (OLED) display panels face issues due to the hysteresis effect of driving transistors, which affects the transfer characteristics of gate voltage during voltage transitions, leading to flicker and fluctuation in image display.
Innovation Solution
A pixel driving circuit is designed with a storage capacitor, a driving transistor, a switch transistor, and a reset transistor. The switch transistor controls the connection or disconnection between the gate electrode of the driving transistor and the storage capacitor, specifically disconnecting during the reset phase and connecting during the data write phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gate electrode of the driving transistor is continuously connected to the storage capacitor, then the driving current can be maintained, but the hysteresis effect causes flicker and grayscale fluctuation
Solution Approach 1:
The switch transistor is turned on in advance during the data write phase to connect the gate electrode to the storage capacitor, ensuring the gate voltage is properly stored before the light emission phase begins. This preliminary connection allows the gate voltage to be established correctly, preventing hysteresis-induced fluctuations during the actual light emission period.
Solution Approach 2:
The switch transistor is periodically switched between on and off states according to different operation phases. It is turned on during the data write phase to connect the gate to the capacitor, and turned off during the light emission phase to disconnect them. This periodic switching eliminates the hysteresis effect by preventing continuous connection while maintaining driving current stability through proper timing.
2Object-affected harmful factors
If the switch transistor is added to control connection/disconnection, then the hysteresis effect is reduced, but the device complexity increases
Solution Approach 1:
The switch transistor is integrated into the existing pixel driving circuit and serves multiple functions: controlling the connection between the gate electrode and storage capacitor, enabling data writing, and eliminating hysteresis effects. By making this single component multi-functional, the circuit complexity is minimized while achieving the desired hysteresis reduction.
Solution Approach 2:
The switch transistor's control terminal is connected to the same scan line that controls other transistors in the pixel circuit, merging the control signals. This integration allows the switch transistor to be controlled by existing signal lines without requiring additional control circuits, thereby reducing overall device complexity while still achieving hysteresis reduction.
Data Source
AI summary
A pixel driving circuit is provided. The pixel driving circuit includes a storage capacitor having a first capacitor electrode and a second capacitor electrode; a driving transistor configured to generate a driving current; a switch configured to control connection or disconnection between a gate electrode of the driving transistor and the first capacitor electrode; and a reset transistor having a first electrode connected to an initialization signal line, a second electrode connected to the first capacitor electrode. The switch includes a transistor comprising a first electrode connected to the first capacitor electrode, a second electrode connected to a gate electrode of the driving transistor, and a gate electrode connected to a scan line. The reset transistor is an n-type transistor. The driving transistor and the transistor of the switch are p-type transistors.