Multi-Channel Lighting Control for Stable Color Point Dimming

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Solution Overview

Problem

Existing multi-channel lighting systems face challenges in achieving accurate color point control and brightness level control due to inherent disadvantages of PWM dimming, such as flickering and the need for current correction, especially when using amplitude modulation ICs, which do not account for non-linear flux versus current relationships and color shifts with different drive currents.

Innovation Solution

A method that iteratively adjusts color point information based on current drive levels and temperature estimates to determine optimal current drive levels for each lighting channel, compensating for non-linear flux and color shifts, allowing for both analog and digital dimming control to maintain a consistent color point across varying brightness levels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If PWM dimming is used for brightness control, then dimming control is achieved, but flickering occurs at low PWM frequencies

Engineering Contradiction:

Improvebrightness controlVSAvoidflickering

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The patent uses periodic PWM dimming signals to control LED brightness, where the duty cycle of the periodic signal determines the average light output. By operating at sufficiently high frequencies, the periodic on-off cycling achieves dimming control while avoiding visible flickering effects.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent changes the PWM frequency parameter to a sufficiently high value where the on-off cycling becomes imperceptible to the human eye, thereby eliminating the harmful flickering effect while maintaining the brightness control functionality.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If PWM dimming with fixed current is used, then LED behavior is predictable, but color point control becomes difficult when using amplitude modulation ICs

Engineering Contradiction:

ImproveLED behavior predictabilityVSAvoidcolor point control accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent segments the brightness control into two independent parts: PWM dimming for overall brightness control with fixed current, and separate amplitude modulation channels for individual LED channel intensity control. This segmentation allows PWM to handle brightness while amplitude modulation handles color point control.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces amplitude modulation as an intermediary mechanism that operates on top of the fixed current PWM system. The amplitude modulation ICs control the effective current through each LED channel, enabling color point adjustment without disrupting the predictable fixed-current behavior provided by PWM.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If current correction is applied for color point variations, then color point accuracy improves, but system complexity increases

Engineering Contradiction:

Improvecolor point accuracyVSAvoidsystem complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies preliminary current correction by pre-calculating and storing the relationship between current levels and color point shifts in lookup tables during the design phase. During operation, the system simply retrieves pre-computed correction values based on the desired brightness level, avoiding complex real-time calculations and reducing system complexity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback by continuously monitoring the actual color point output and comparing it with the target color point. The system then adjusts the amplitude modulation parameters to compensate for any deviations, maintaining accurate color point control while adapting to variations in LED characteristics and aging effects.

Inventive Principle:

Principle #23Feedback

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables precise control of color point and brightness levels by iteratively adjusting current drive levels, ensuring consistent color point performance regardless of brightness changes, and improving dimming resolution through combined amplitude modulation and PWM dimming strategies.

Implementation Method 1

a plurality of lighting channels with light sources having different color points

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Implementation Method 2

there is an increasing focus in the integrated circuit, IC, industry on ICs with amplitude modulation dimming capabilities

Methodology Applied

Scientific EffectAmplitude modulation:

Implementation Method 3

PWM dimming is very attractive since the LED behavior can be well predicted

Methodology Applied

Scientific EffectPulse width modulation:

Data Source

PatentUS12538398B2Control of a lighting system for color point and flux level control

Publication Date: 2026.01.27 SIGNIFY HOLDING BV

AI summary

A method is provided for controlling a multi-channel lighting system in which (nominal) color point information in respect of the light sources is adjusted both in dependence on a temperature estimate and on the current drive levels needed. The method thus compensates separately for the light source temperature and the effect that the calculated current drive levels have on the color point and flux. An iterative loop finds the current drive levels to achieve a desired color point and flux.