PWM Pixel Circuit With Threshold Compensation for High-Resolution Displays
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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 devices.
Innovation Solution
A pixel circuit design with a reduced number of transistors and capacitors, utilizing a first circuit block for emission control and a second circuit block for driving current generation, with specific transistor types and capacitors to enable internal threshold voltage compensation, suitable for ultra-high-resolution displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pixel circuit design with pulse width modulation and internal threshold voltage compensation is used, then threshold voltage compensation and PWM driving are achieved, but the number of transistors and capacitors increases to 19 or more, making integration difficult for ultra-high-resolution display devices
Solution Approach 1:
The patent combines multiple functions into a reduced transistor count by merging the emission control function and driving current generation function into an integrated circuit structure. The first circuit block generates emission control signals that directly modulate the light-emitting element, while the second circuit block generates driving current, eliminating the need for separate control circuits and reducing the total transistor and capacitor count while maintaining threshold voltage compensation capability
Solution Approach 2:
The circuit blocks are designed to perform multiple functions simultaneously. The first circuit block both controls emission timing and generates control signals for the light-emitting element, while the second circuit block both generates driving current and responds to emission control signals. This multi-functionality reduces the overall component count while maintaining PWM driving and threshold voltage compensation
2Device complexity
If a reduced number of transistors is used in the pixel circuit, then integration is improved for ultra-high-resolution displays, but the circuit complexity is reduced which may affect the ability to perform internal compensation and PWM driving
Solution Approach 1:
The pixel circuit performs internal compensation of threshold voltage automatically through its circuit configuration. The first circuit block with the first transistor and capacitor automatically compensates for threshold voltage variations without requiring external intervention or additional compensation circuits, enabling the reduced transistor design to maintain reliable threshold voltage compensation capability
3Device complexity
If the number of transistors is reduced to improve integration, then the pixel circuit can be applied to ultra-high-resolution display devices, but the hysteresis characteristics and emission efficiency may be compromised
Solution Approach 1:
The patent optimizes the parameters of the remaining transistors and capacitors to maintain hysteresis characteristics and emission efficiency. By carefully selecting transistor types (N-type and P-type), capacitor values, and voltage levels (first reference voltage, second reference voltage, pixel data voltage), the circuit achieves stable emission control and efficient light-emitting element operation with fewer transistors
Data Source
AI summary
A pixel circuit includes a first circuit block and a second circuit block. The first circuit block includes a first transistor including a control electrode connected to a first node, a first electrode connected to a second node and a second electrode connected to a third node, a second transistor which applies the pulse data voltage to a fourth node in response to a write gate signal, a third transistor which connects the third node and the fourth node in response to a compensation gate signal, a fourth transistor which applies a first reference voltage to the second node in response to a first emission signal, a fifth transistor which applies the sweep signal to the third node in response to a second emission signal and a first capacitor including a first electrode connected to the first node and a second electrode connected to the fourth node.