Oxide Semiconductor Driving Transistor for Low-Frequency Display Flicker
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Solution Overview
Problem
Light emitting display apparatuses experience flickering due to changes in threshold voltages and hysteresis characteristics of driving transistors, leading to variations in luminance during refresh and anode reset periods, especially when driven at low frequencies to reduce power consumption.
Innovation Solution
The use of an oxide semiconductor for the driving transistor in the pixel driving circuit, combined with a specific timing scheme where the switching transistor is turned on only during the refresh period and the driving transistor is formed of an oxide semiconductor, ensuring consistent luminance by maintaining data voltage during both periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the light emitting display apparatus is driven at low frequencies to reduce power consumption, then power consumption is reduced, but threshold voltages of driving transistors and hysteresis characteristics change causing luminance variation and flicker
Solution Approach 1:
The patent changes the material parameter of the driving transistor from conventional semiconductor to oxide semiconductor, which fundamentally alters the electrical characteristics to achieve stable threshold voltage and minimal hysteresis across different driving frequencies, thereby maintaining luminance consistency while enabling low-power operation
Solution Approach 2:
The patent employs oxide semiconductor material with specific compositional characteristics (such as In-Ga-Zn-O system) to create a driving transistor that combines the benefits of low leakage current with stable electrical characteristics, resolving the contradiction between power consumption and luminance consistency
2Use of energy by moving object
If data voltages are supplied only during refresh period to reduce power consumption, then power consumption is reduced, but the light emitting device cannot be properly controlled during anode reset period causing abnormal operation
Solution Approach 1:
The oxide semiconductor driving transistor maintains its electrical characteristics and stored charge stability during the anode reset period without requiring additional voltage supply, enabling the circuit to self-maintain proper operation states and allowing the switching transistor to remain off for power savings
Data Source
AI summary
A light emitting display apparatus includes a pixel including a pixel driving circuit and a light emitting device, and a gate driver supplying gate signals to the pixel driving circuit. The pixel driving circuit includes a switching transistor, a driving transistor, and a first light emitting transistor. The first light emitting transistor is connected between an anode of the light emitting device and a first node, the driving transistor controls the size of the current supplied to the light emitting device through the first node and the first light emitting transistor, and the switching transistor controls the supply of a data voltage to the light emitting device through the first node. During the use of the light emitting display apparatus, one second is divided into a refresh period and an anode reset period, and the switching transistor is turned on only during the refresh period.