PWM Pixel Circuit With Global Sweep Threshold Compensation
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Solution Overview
Problem
Conventional pixel circuits driven by pulse width modulation and performing internal threshold voltage compensation require a large number of transistors and capacitors, making them unsuitable for ultra-high-resolution display applications.
Innovation Solution
A pixel circuit design with a reduced number of transistors and capacitors, utilizing P-type and N-type transistors, and employing global signals for synchronization, enabling efficient internal threshold voltage compensation and low power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pixel circuits with internal threshold voltage compensation are used, then threshold voltage compensation is achieved, but the number of transistors and capacitors increases making ultra-high-resolution display inapplicable
Solution Approach 1:
The patent merges the emission control function from a separate emission driver into the pixel circuit itself. The first transistor in the pixel circuit directly responds to the emission signal to control the light emitting element, eliminating the need for dedicated emission control transistors in a separate driver circuit. This integration reduces the overall transistor count while maintaining threshold voltage compensation functionality.
Solution Approach 2:
The first transistor in the pixel circuit serves multiple functions: it acts as the emission control switch responsive to the emission signal, and simultaneously participates in the threshold voltage compensation mechanism through its connection to the capacitor. This multi-functionality reduces the total number of components needed while achieving both emission control and threshold compensation.
2Measurement precision
If more transistors and capacitors are used for internal compensation, then compensation precision is improved, but integration density decreases
Solution Approach 1:
The emission control function is merged into the pixel circuit's existing transistor structure. The first transistor handles both emission control and threshold compensation operations, allowing precise compensation to be achieved without adding extra components that would reduce integration density.
Solution Approach 2:
The first transistor performs dual functions as both the emission control switch and the compensation transistor. This multi-functional design maintains compensation precision while optimizing integration density by avoiding redundant components.
3Ease of operation
If conventional emission control with separate driver is used, then control functionality is complete, but device complexity and power consumption increase
Solution Approach 1:
The emission control function is extracted from the separate emission driver circuit and integrated directly into the pixel circuit. The first transistor in the pixel circuit now directly responds to the emission signal, eliminating the need for dedicated emission control transistors in the external driver, thus reducing overall device complexity.
Solution Approach 2:
The emission control functionality is merged into the pixel circuit's internal transistor structure. The first transistor serves as the emission switch, combining what were previously separate functions (emission control and pixel operation) into a single integrated unit, reducing driver circuit complexity.
4Speed
If P-type transistors are used for emission control, then mobility is improved, but power consumption increases
Solution Approach 1:
The patent employs dynamic control of the first transistor using the emission signal. The transistor is activated only during the emission period rather than continuously, which optimizes the balance between utilizing P-type transistor mobility benefits and minimizing power consumption by reducing the duration of high-current operation.
Data Source
AI summary
A pixel circuit includes a first transistor, a second transistor for applying a data voltage to the first transistor, a third transistor for diode-connecting the first transistor, a fourth transistor for applying a first power voltage to a first electrode of the first transistor, a fifth transistor for connecting a second electrode of the first transistor and a fourth node, a sixth transistor for applying an initialization voltage, a seventh transistor, an eighth transistor for applying the data voltage to a fifth node in response to a second scan signal, a tenth transistor for applying a second power voltage to the fifth node, a twelfth transistor for applying the initialization voltage to the fourth node and a light emitting element. A sweep signal is applied to a control electrode of the first transistor, and the sweep signal is a global signal which has same timing across at least two pixel-rows.