Pixel Circuit Offset Voltage Compensation for High-Temperature Brightness
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Solution Overview
Problem
The efficiency of light-emitting diodes in display panels decreases with increasing temperature, leading to a reduction in brightness.
Innovation Solution
A pixel circuit that includes a driving transistor, a light-emitting circuit, and a controlling circuit, which generates an offset voltage to adjust the driving current based on the temperature of the light-emitting element, compensating for brightness changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the light-emitting diode operates at high temperature, then the operating time is extended, but the light-emitting efficiency decreases and brightness is lowered
Solution Approach 1:
The patent changes the voltage parameter dynamically by introducing an offset voltage that varies with temperature. The controlling circuit adjusts the first voltage at the first node based on temperature-dependent offset voltages, thereby modifying the driving current characteristics to compensate for temperature-induced efficiency changes and maintain brightness stability over extended operating periods
Solution Approach 2:
The patent implements a feedback mechanism where the controlling circuit monitors the offset voltage generated by the light-emitting circuit and uses this information to adjust the first voltage at the first node. This feedback loop enables the system to adaptively compensate for temperature effects on light-emitting efficiency, maintaining consistent brightness throughout the operating cycle
2Device complexity
If a conventional driving circuit is used without temperature compensation, then the device complexity is low, but the brightness consistency deteriorates at varying temperatures
Solution Approach 1:
The controlling circuit performs multiple functions: it generates the first voltage for the driving transistor, adjusts this voltage based on offset voltage feedback, and compensates for temperature effects on the light-emitting element. By integrating these functions into a single circuit block, the patent achieves brightness consistency without proportionally increasing overall device complexity
Solution Approach 2:
The offset voltage acts as an intermediary signal that carries temperature information from the light-emitting circuit to the controlling circuit. This intermediary enables the controlling circuit to indirectly sense temperature effects and adjust the driving voltage accordingly, maintaining brightness consistency through a relatively simple mediation mechanism rather than direct temperature sensing
Data Source
AI summary
A pixel circuit and a display panel are provided. The pixel circuit includes a driving transistor, a light-emitting circuit, and a controlling circuit. The light-emitting circuit is coupled between the driving transistor and a light-emitting element. The controlling circuit is coupled to the light-emitting circuit and is coupled to the driving transistor at a first node. The controlling circuit sets a first voltage at the first node based on reference voltages according to controlling signals. During a light-emitting period, the light-emitting circuit generates an offset voltage on a first terminal of the light-emitting element according to a light-emitting signal, such that the controlling circuit sets the first voltage based on the offset voltage according to the controlling signals. Further, the driving transistor generates a driving current to the light-emitting element according to the first voltage, so that brightness of the light-emitting element at a high temperature is compensated.