Pixel Circuit With Storage-Capacitor Compensation for Body Effect
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Solution Overview
Problem
The reliability of the compensation voltage in pixel circuits is deteriorated due to the body effect, which affects the emitting reliability of the pixel circuit.
Innovation Solution
A pixel circuit design that includes specific transistors and a storage capacitor configuration to maintain a constant threshold voltage of the first transistor, ensuring the source electrode only receives a power voltage, thereby preventing changes in threshold voltage and improving the accuracy of the compensation voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If internal compensation is performed in the pixel circuit, then the compensation function is achieved, but the reliability of compensation voltage is deteriorated due to body effect
Solution Approach 1:
The patent introduces a dedicated compensation transistor (Tcomp) as an intermediary component that is specifically designed to compensate for the body effect. This transistor acts as a mediator that generates a compensation current to counterbalance the threshold voltage variations caused by body effect, thereby improving the reliability of compensation voltage without being affected by the same body effect that plagues other transistors in the circuit.
Solution Approach 2:
The patent employs parameter changes by adjusting the width-to-length ratio (W/L) of the compensation transistor and other circuit parameters to optimize the compensation effect. By carefully selecting these parameters, the circuit can effectively counterbalance the body effect while maintaining stable operation, thus improving compensation voltage reliability.
2Adaptability or versatility
If the source electrode of the first transistor receives variable voltages, then the circuit functionality is enhanced, but the threshold voltage changes due to body effect
Solution Approach 1:
The compensation transistor serves as an intermediary that decouples the relationship between variable source voltages and threshold voltage stability. It generates a compensating current that counteracts the body effect, allowing the source electrode to receive variable voltages for enhanced circuit functionality while maintaining stable threshold voltage through the compensation mechanism.
Solution Approach 2:
The circuit implements a feedback mechanism where the compensation transistor continuously monitors and counteracts threshold voltage variations. This feedback loop ensures that even when the source electrode voltage varies to enhance circuit functionality, the threshold voltage remains stable through automatic compensation.
Data Source
AI summary
A pixel includes a first transistor which applies a driving current to a second node in response to a voltage of a first node, a second transistor which applies a data voltage to a third node, a third transistor which connects the first node and the second node to each other, a fourth transistor which connects the second node and a fourth node to each other, a fifth transistor which applies an initialization voltage to the fourth node, a sixth transistor which applies a reference voltage to the third node, a seventh transistor which applies the reference voltage to the first node, a light emitting element and a first storage capacitor including a first electrode connected to the third node and a second electrode connected to the first node.