LED String Driving Control for Stable Brightness at Low Battery Voltage

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Solution Overview

Problem

LED lighting devices experience brightness reduction due to decreased battery voltage, causing the current controller to fail in maintaining consistent LED power.

Innovation Solution

An LED driving device that senses voltage through an LED string unit to select driving conditions and adjusts current flow so that the sum of power for some LEDs and all LEDs remains consistent, regardless of battery voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If battery voltage decreases due to external or internal environments, then power consumption is reduced, but LED brightness decreases because current controller fails to maintain current control

Engineering Contradiction:

Improvepower consumptionVSAvoidLED brightness

Core Design Contradiction:

Use of energy by moving objectVSIllumination intensity

Solution Approach 1:

The patent applies dynamics by making the LED string configuration adjustable between series and parallel connections based on battery voltage conditions. The controller dynamically switches between full-series connection (for low voltage/high efficiency) and partial-series connection (for high voltage/brightness), resolving the contradiction between power consumption and brightness maintenance.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the electrical connection parameter of LED strings from fixed series to variable series-parallel configuration. By changing the connection topology based on voltage thresholds, the system maintains optimal current control and brightness while adapting to varying battery voltage conditions.

Inventive Principle:

Principle #35Parameter changes

2Illumination intensity

If more LEDs are used to increase design complexity and brightness, then illumination intensity improves, but device complexity increases

Engineering Contradiction:

ImprovebrightnessVSAvoidnumber of LEDs

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

The patent segments the LED strings into multiple independent groups that can be selectively activated or deactivated. By dividing the LED array into controllable segments, the system can adjust brightness through selective activation rather than increasing total LED count, thereby reducing device complexity while maintaining illumination flexibility.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS20260107355A1LED driving device and LED lighting device comprising same

Publication Date: 2026.04.16 LX SEMICON CO LTD

AI summary

Provided are: an LED driving device for maintaining LED power regardless of battery voltage; and an LED lighting device including same, the LED driving device comprising: a selection unit, which senses voltage flowing into an LED string unit so as to select an LED driving condition of the LED string unit on the basis of the sensed voltage; and a current control driving unit for controlling an LED current such that some LEDs or all LEDs of the LED string unit are driven in correspondence to the LED driving condition of the selection unit, wherein the current control driving unit can adjust a current flowing into each LED so that the total LED power corresponding to the driving of the some LEDs and the total LED power corresponding to the driving of all of the LEDs are the same.