Pixel Circuit Layout for PWM Compensation With Fewer Transistors

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Solution Overview

Problem

Conventional pixel circuits for ultra-high resolution displays, driven in pulse width modulation with internal threshold voltage compensation, require 19 or more transistors and 3 or more capacitors, limiting their integration and suffering from afterimage, response time, and luminance characteristics degradation due to P-type driving transistors.

Innovation Solution

A pixel circuit design with fewer transistors, including 10 transistors and 2 capacitors, utilizing N-type and P-type transistors, and employing internal threshold voltage compensation, enabling high integration and improved performance in ultra-high resolution displays.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional pixel circuit design with P-type driving transistor is used, then pulse width modulation and internal threshold voltage compensation can be achieved, but transistor count increases to 19 or more and afterimage characteristic deteriorates

Engineering Contradiction:

Improveafterimage characteristicVSAvoidtransistor count

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent inverts the transistor type used for the driving transistor from P-type to N-type. This inversion resolves the contradiction by improving afterimage characteristic and response time while reducing the total transistor count to 10, eliminating the need for additional transistors that would be required in conventional P-type designs.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the fundamental parameter of transistor type (from P-type to N-type) to achieve superior performance characteristics. This parameter change enables the circuit to maintain pulse width modulation and internal threshold voltage compensation functionality while using fewer transistors and improving display characteristics.

Inventive Principle:

Principle #35Parameter changes

2Speed

If conventional pixel circuit with P-type driving transistor is used, then internal compensation of threshold voltage can be operated, but response time characteristic when changing from black image to white image deteriorates

Engineering Contradiction:

Improveresponse time characteristicVSAvoidtransistor count

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

By inverting the driving transistor from P-type to N-type, the patent achieves faster response time characteristics when transitioning from black to white images. The N-type transistor provides improved electron mobility and faster switching speed, reducing the response time without requiring additional transistors.

Inventive Principle:

Principle #13The other way round (Inversion)

3Temperature

If conventional pixel circuit with P-type driving transistor is used, then pulse width modulation can be implemented, but luminance changing rate characteristic according to temperature deteriorates

Engineering Contradiction:

Improveluminance changing rate characteristicVSAvoidtransistor count

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The patent inverts the driving transistor type to N-type, which provides better temperature stability and luminance changing rate characteristics. The N-type transistor's lower on-resistance and higher mobility result in more stable luminance output across temperature variations while maintaining the pulse width modulation function with fewer transistors.

Inventive Principle:

Principle #13The other way round (Inversion)

4Ease of manufacture

If pixel circuit includes 19 or more transistors and 3 or more capacitors, then pulse width modulation and internal compensation can be achieved, but integration limitation occurs

Engineering Contradiction:

ImproveintegrationVSAvoidtransistor count

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The patent merges multiple functions into a unified circuit design with only 10 transistors and 2 capacitors. By integrating the driving transistor, constant current generation, and pulse width modulation functions into a compact structure, the patent achieves high integration suitable for ultra-high resolution displays without requiring the 19+ transistors and 3+ capacitors of conventional designs.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS20250372026A1Pixel circuit and electronic apparatus including the same

Publication Date: 2025.12.04 SAMSUNG DISPLAY CO LTD

AI summary

A pixel circuit includes a first transistor, a second transistor, a third transistor, a seventh transistor, a ninth transistor and a light emitting element. The first transistor includes 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. The second transistor is connected to the first node and the second node. The third transistor is configured to apply a data voltage to the first transistor. The seventh transistor is connected to a fourth node and configured to apply a driving current to the light emitting element. The ninth transistor is configured to apply a constant-current voltage to the fourth node. The light emitting element is configured to emit a light based on the data voltage and the constant-current voltage. The first transistor is an N-type transistor. The seventh transistor is a P-type transistor.