LED Backlight Pixel Circuit Sharing to Reduce FALD Complexity
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Solution Overview
Problem
The increasing use of full array local dimming (FALD) in display panels requires a large number of LED elements and pixel circuits, leading to increased manufacturing complexity, cost, and reduced efficiency.
Innovation Solution
A display device with a light-emitting diode (LED) backlight unit (BLU) that separates pixel circuits and pixel driving circuits, utilizing a current mirror structure and additional circuits like current boosting and de-ghost circuits to control output current and luminance, reducing the number of circuits needed for driving the display panel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If full array local dimming (FALD) is implemented with a large number of LED elements, then contrast performance is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines multiple pixel circuits to drive a single LED element, creating a shared driving architecture. Specifically, multiple pixel circuits (e.g., 4x4=16 circuits) share one LED element, reducing the total number of LED elements required while maintaining the local dimming functionality and contrast performance.
Solution Approach 2:
The patent makes LED elements serve multiple functions by having them be driven by multiple different pixel circuits. A single LED element can be controlled by multiple pixel circuits depending on the display content requirements, increasing system versatility while reducing component count.
2Measurement precision
If the number of pixel circuits is increased to drive more LED elements, then luminance control precision is improved, but manufacturing cost and complexity increase
Solution Approach 1:
The patent merges multiple pixel circuits to control a single LED element, maintaining precise luminance control through the collaborative operation of multiple circuits while reducing the overall component count and manufacturing complexity.
Solution Approach 2:
The patent uses current mirror structures to replicate and transfer control signals between pixel circuits. The current mirror circuit copies the output current from one pixel circuit to control another LED element, ensuring consistent luminance control precision across multiple shared elements without requiring independent control circuits for each.
3Device complexity
If multiple pixel circuits share a single LED element, then device complexity is reduced, but control difficulty increases
Solution Approach 1:
The current mirror structure automatically copies control signals between pixel circuits, eliminating the need for complex manual coordination. The mirror circuit replicates the control voltage or current, ensuring synchronized operation of multiple circuits sharing an LED element without increasing operational difficulty.
Solution Approach 2:
The pixel circuits automatically coordinate their operation through the shared LED element and current mirror structures. The system self-regulates by having each pixel circuit independently control its share of LED elements, with the physical circuit architecture ensuring proper signal distribution and timing without external intervention.
Data Source
AI summary
A display device may include: a light-emitting diode (LED) backlight unit (BLU), a pixel driving circuit configured to generate a scan signal and an image signal, a pixel circuit configured to generate an output current based on the scan signal and the image signal, and transmit the output current to the LED BLU, the pixel circuit including, a first transistor connected between an input pin and a node, the input pin configured to receive the image signal, the first transistor including a gate terminal configured to receive the scan signal, a second transistor connected between the node and a ground terminal, the second transistor including a gate terminal connected to the node, a third transistor connected between the node and a gate node, a fourth transistor configured to generate the output current according to a voltage of the gate node, and a capacitor connected to the gate node.