IR-Independent Pre-Charge Circuit for Display Uniformity

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Solution Overview

Problem

As electronic display panels grow larger, pre-charging display pixels farther from the voltage source results in significant IR drop, leading to loss of uniformity due to varying voltage levels across the display. Additionally, the use of non-inverting buffers can cause IR error to accumulate on one voltage source, increasing peak panel current and power consumption.

Innovation Solution

The implementation of an analog buffer and sampling capacitor to provide an IR-independent pre-charge voltage, and the use of inverters to distribute IR drop evenly across positive and negative voltage sources, reducing static power consumption and peak panel current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If display pixels are pre-charged using conventional voltage sources, then the display pixels can be charged to threshold voltage level, but IR drop increases with distance from voltage source causing non-uniform voltage levels across the display

Engineering Contradiction:

Improvedisplay uniformityVSAvoiddisplay panel size

Core Design Contradiction:

Manufacturing precisionVSLength of moving object

Solution Approach 1:

The patent divides the display panel into multiple regions with separate pre-charge voltage sources positioned at different locations. Each region receives pre-charge voltage from a nearby source, minimizing the distance and resulting IR drop for all pixels in that region. This segmentation approach ensures uniform voltage levels across the entire display regardless of overall panel size.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces buffer circuits as intermediaries between the pre-charge voltage sources and the display pixels. These buffers compensate for IR drops by actively adjusting voltage levels, ensuring that even pixels far from the voltage sources receive the correct pre-charge voltage. The buffers act as mediators that eliminate the harmful effect of distance-related voltage loss.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If non-inverting buffers are used to transmit data, then data transmission is simplified, but IR error accumulates on one voltage source increasing peak panel current and power consumption

Engineering Contradiction:

Improvebuffer circuit complexityVSAvoidpower consumption

Core Design Contradiction:

Device complexityVSUse of energy by moving object

Solution Approach 1:

The patent employs inverting buffers instead of non-inverting buffers to transmit data signals. The inverting buffers swap the logic levels (0 becomes 1, 1 becomes 0), which causes the current flow direction to reverse during switching transitions. This inversion distributes the current demand across multiple voltage sources (VDD and VSS) rather than concentrating it on one source, thereby reducing peak panel current and power consumption while maintaining data transmission functionality.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS12340736B2Systems and methods for IR-independent pre-charge and inverter- based IR reduction

Publication Date: 2025.06.24 APPLE INC

AI summary

In an embodiment, an electronic display may include an electronic display panel that includes a plurality of display pixels configured to emit light; a first pre-charge voltage source; and a second pre-charge voltage source; and a microdriver that may include: a capacitor coupled at a first terminal to the first pre-charge voltage source and coupled at a second terminal to the second pre-charge voltage source; and a buffer. The buffer may include a positive input terminal coupled to the first pre-charge voltage source and the capacitor; an output terminal coupled to a plurality of driving circuits; and a negative input terminal coupled to the output terminal.