Driving Circuit With Capacitive Switching for Fast Grayscale Control
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Solution Overview
Problem
Current display technologies face issues with long transition times of driving currents in pixel circuits, leading to waveform distortion at low grayscale conditions and increased power consumption due to additional transistors in the current path, affecting the efficiency of light-emitting elements.
Innovation Solution
A driving circuit design utilizing a two-stage path controlled by switching transistors and capacitors to reduce transition time through a fast rising mechanism, precisely controlling grayscale intensity and reducing the number of transistors in the current path, thereby minimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If more transistors are disposed on the current path to ensure the driving transistor operates in saturation region, then the operating reliability is improved, but the voltage between driving voltage terminals increases resulting in increased power consumption
Solution Approach 1:
The patent segments the transistor configuration into a driving transistor and separate switching transistors. The driving transistor is dedicated to controlling the light emitting element with proper saturation region operation, while switching transistors handle the grayscale control function. This segmentation allows each transistor to perform its optimal function without requiring excessive transistors in the current path, thus maintaining reliability while reducing voltage drop and power consumption.
Solution Approach 2:
The patent extracts the grayscale control function from the main current path by introducing separate switching transistors that control the driving transistor's gate voltage. This extraction allows the driving transistor to maintain saturation region operation for reliable light emission while the switching transistors independently manage grayscale dimming, preventing the need for additional transistors in the current path that would increase power consumption.
2Reliability
If the transition time of driving current is increased to ensure proper operation, then the operating reliability is improved, but waveform distortion occurs at low grayscale condition and light emitting element efficiency decreases
Solution Approach 1:
The patent applies preliminary action by using switching transistors to pre-establish the appropriate gate voltage for the driving transistor before the light emitting element needs to emit light. The switching transistors are controlled to charge or discharge the driving transistor's gate capacitor in advance, ensuring the driving transistor reaches the correct operating state quickly and accurately. This preliminary preparation enables fast transition times without waveform distortion while maintaining reliability.
Solution Approach 2:
The patent introduces dynamic control through switching transistors that can rapidly adjust the driving transistor's gate voltage based on the required grayscale level. This dynamic switching capability allows the driving current transition time to be optimized for each grayscale condition, achieving fast response for low grayscale levels while maintaining proper saturation region operation for reliability, thereby eliminating waveform distortion.
3Productivity
If the transition time of driving current is reduced to improve response speed, then productivity is improved, but waveform distortion occurs at low grayscale condition
Solution Approach 1:
The patent introduces switching transistors as intermediary devices between the control signals and the driving transistor. These switching transistors act as mediators that rapidly switch the driving transistor's gate voltage to achieve fast response times. By placing the switching transistors in parallel with the driving transistor's gate capacitor, the circuit can quickly charge or discharge the capacitor without affecting the driving transistor's saturation region operation, thus achieving fast response speed while preventing waveform distortion at low grayscale levels.
Data Source
AI summary
A driving circuit includes a driving transistor, first to second capacitors and first to third switching transistors. The driving transistor is configured to control a driving current provided to a light emitting element to emit light. The first capacitor includes a first terminal coupled to a gate terminal of the driving transistor. The first switching transistor coupled between a second terminal of the first capacitor and a driving voltage terminal. The second switching transistor includes a first terminal coupled to a gate terminal of the first switching transistor and a second terminal coupled to a first reference voltage terminal. The third switching transistor coupled between a gate terminal of the second switching transistor and a second reference voltage terminal. The second capacitor includes a first terminal coupled to a gate terminal of the third switching transistor and a second configured to receive a sweep signal.