Driving Circuit Low Grayscale Control via Transistor Conduction Overlap
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Solution Overview
Problem
The existing driving circuits for LED light-emitting devices face difficulties in displaying low grayscales due to the minimum conduction time requirement of transistors, making it challenging to achieve accurate low grayscale displays.
Innovation Solution
A driving circuit design that incorporates a grayscale controlling module with two transistors, where the conduction time of one transistor partially overlaps with the other, allowing for a light-emitting duration shorter than the minimum conduction time of either transistor, controlled by phase-differentiated controlling signals to manage the light-emitting duration effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the driving circuit uses a single transistor to control the light-emitting device, then the circuit structure is simple, but the minimum light-emitting duration is limited by the transistor's minimum conduction time, making it difficult to display low grayscales
Solution Approach 1:
The patent divides the single transistor control function into two separate transistors (first transistor and second transistor) that work in sequence. The first transistor controls the initial conduction phase, and the second transistor controls the subsequent conduction phase. This segmentation allows the light-emitting device to be controlled for durations shorter than the minimum conduction time of a single transistor, enabling low grayscale display while maintaining relatively simple circuit structure.
2Reliability
If the light-emitting duration is extended to meet the minimum conduction time of the transistor, then the transistor can operate reliably, but the ability to display low grayscales is lost
Solution Approach 1:
The patent uses periodic control signals with different phases to drive the first and second transistors. The first transistor is controlled by a first control signal, and the second transistor is controlled by a second control signal that is phase-shifted relative to the first. This periodic action with phase difference allows the circuit to achieve reliable transistor operation while enabling precise control of the light-emitting duration for accurate grayscale display.
3Measurement precision
If the conduction time of the transistor is reduced to achieve low grayscale display, then the grayscale precision is improved, but the transistor may not have sufficient time to fully conduct, affecting reliability
Solution Approach 1:
The patent applies preliminary action by having the first transistor conduct before the second transistor. The first transistor is turned on in advance to prepare the current path, and then the second transistor is turned on to complete the conduction. This preliminary action ensures that the transistor has sufficient time to fully conduct and establish stable current flow, while still achieving the overall short light-emitting duration needed for low grayscale display.
Data Source
AI summary
A driving circuit and a display panel are provided. The driving circuit includes a light-emitting device, a light-emitting controlling module, and a grayscale controlling module. The grayscale controlling module includes a first transistor and a second transistor. A conduction time of the first transistor partially overlaps the conduction time of the second transistor to realize that a light-emitting duration of the light-emitting device is less than a minimum conduction time of the first transistor or the minimum conduction time of the second transistor.