LED Backlight Circuit Low-Potential Switch Control

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing LED backlight driving circuits face high hardware and control costs in direct drive mode and suffer from 'ghosting' and limited brightness control in row-column scanning mode, which restricts individual LED string brightness adjustment and display quality.

Innovation Solution

An LED backlight driving circuit using low-potential-end switch control, where multiple LED strings share a constant current module and a channel switching control module adjusts the duty cycle of each string based on required brightness, eliminating the need for row scanning at the high-potential-end and allowing independent brightness control of each string.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If direct drive mode is used with independent constant current source for each LED string, then individual brightness control of each LED string is achieved, but hardware cost and control complexity increase significantly

Engineering Contradiction:

ImproveIndividual brightness controlVSAvoidHardware cost

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Multiple LED strings share a common constant current source module, merging what were previously separate independent current sources. This reduces the number of current source modules needed while still enabling individual brightness control through the low-potential-end switch control mechanism

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

Instead of controlling LED strings from the high-potential-end (anode) as in conventional approaches, the patent controls them from the low-potential-end (cathode). This inversion allows multiple strings to share a common current source while maintaining individual control capability through duty cycle adjustment of the low-potential-end switches

Inventive Principle:

Principle #13The other way round (Inversion)

2Device complexity

If row-column scanning drive mode is used to simplify circuit structure, then hardware cost is reduced, but individual LED string brightness adjustment becomes impossible and ghosting phenomenon occurs

Engineering Contradiction:

ImproveCircuit structureVSAvoidIndividual brightness control

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent inverts the conventional scanning approach by controlling LED strings from the low-potential-end rather than the high-potential-end. This allows duty cycle control to be applied effectively while sharing a common current source, achieving both circuit simplification and individual brightness control

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent implements dynamic duty cycle control for each LED string's low-potential-end switch, allowing the on-time ratio to be adjusted independently for each string. This dynamic control enables individual brightness adjustment while maintaining the simplified shared current source architecture

Inventive Principle:

Principle #15Dynamics

3Device complexity

If row-column scanning mode shares constant current source among multiple LED strings, then hardware cost is reduced, but brightness upper limit is constrained by shared duty cycle

Engineering Contradiction:

ImproveHardware costVSAvoidBrightness level

Core Design Contradiction:

Device complexityVSIllumination intensity

Solution Approach 1:

The patent applies dynamic duty cycle control to each individually controllable LED string driven from the low-potential-end. This allows strings that need higher brightness to operate at higher duty cycles while sharing the common current source, overcoming the uniform brightness limitation of conventional scanning modes

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the control parameter from uniform duty cycle allocation in row-column scanning to individualized duty cycle allocation based on low-potential-end switch control. This parameter change enables different brightness levels for different LED strings while maintaining hardware simplicity

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12154521B1Method for driving LED backlight driving circuit based on low-potential-end switch control

Publication Date: 2024.11.26 X SIGNAL INTEGRATED CO LTD

AI summary

An LED backlight driving circuit based on low-potential-end switch control and a backlight driving method are provided. The LED backlight driving circuit includes a plurality of LED strings, a channel control switch device, a constant current module, a channel switching control module, a signal control unit, and an SPI interface unit. Each of the LED strings has a high-potential-end directly connected to an LED driving voltage VLED and a low-potential-end connected to one channel control switch device and one constant current module, and a plurality of channel control switch devices in each group of LED strings are connected to one channel switching control module; and the channel switching control module is used to control the on-state duty cycle of the LED strings in the group.