SMPS Inductor for LED Color Consistency

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The existing lighting systems with multiple LED strings in parallel experience color shifts due to voltage imbalances, leading to undesirable current changes and light output variations when driven by a single DC/DC converter, causing color spread and inefficiencies in control.

Innovation Solution

Incorporating a parallel inductor between the output of the switched mode power supply and the LED loads, which acts as a real current source, reducing capacitive behavior and minimizing current steps caused by voltage changes, allowing for independent control of LED strings and reducing color shifts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If multiple LED strings are connected in parallel with different forward voltages to a single DC/DC converter, then cost is reduced and design flexibility is improved, but color spread and light output instability occur due to voltage imbalances and current steps

Engineering Contradiction:

ImprovecostVSAvoidcolor consistency

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

An additional inductor is introduced as an intermediary element between the DC/DC converter output and the parallel LED strings. This inductor acts as a current buffer that decouples the voltage imbalances between different LED strings, preventing direct voltage conflicts and current steps while maintaining cost-effective single converter architecture

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the electrical parameters at the converter output by adding inductance, transforming the output characteristics from voltage-dominated to current-stabilized. This parameter change allows the system to accommodate LED strings with different forward voltages without causing color spread

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If a large buffer capacitor is used at the DC/DC converter output to stabilize voltage, then voltage stability is improved, but color shift increases due to energy transfer between capacitors and LED strings with different voltages

Engineering Contradiction:

Improvevoltage stabilityVSAvoidcolor point stability

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The additional inductor serves as a mediator between the buffer capacitor and the LED strings, controlling the energy transfer process. It prevents direct capacitive coupling between the buffer capacitor and LED strings with different forward voltages, thereby eliminating the harmful energy transfer that causes color shifts

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention substitutes the purely capacitive energy storage system with an inductive-capacitive combination. The inductor provides current continuity and controls energy release, replacing the direct capacitive discharge mechanism that causes voltage steps and color shifts

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of operation

If switches are opened or closed to control LED strings, then light output control is achieved, but voltage steps are created across the output capacitor causing current steps and negative impact on light output

Engineering Contradiction:

Improvelight controlVSAvoidvoltage steps and current steps

Core Design Contradiction:

Ease of operationVSObject-generated harmful factors

Solution Approach 1:

The additional inductor provides beforehand cushioning by storing energy in its magnetic field before switch transitions occur. This cushioning effect smooths out the voltage steps that would otherwise be created by sudden switch operations, preventing harmful current steps in the LED strings

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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

This solution stabilizes current flow, reduces color shifts, and enables efficient control of LED strings, allowing for flexible and optimized light output with reduced ripple and improved color consistency, even with unequal string voltages.

Implementation Method 1

a further inductor coupled between one of the output pins and the input of the load

Methodology Applied

Scientific EffectInductance: Inductor

Implementation Method 2

a switched mode power supply comprising: a switching element; an inductor; a diode; a set of output pins for coupling to the load; and a capacitor coupled across the set of output pins

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentEP4000352B1Improved balance control for 2-channel cct dimming

Publication Date: 2023.09.06 SIGNIFY HOLDING BV

Figure 1
Figure 2A
Figure 2B

AI summary

The invention relates to a lighting system comprising a load comprising a parallel configuration of a first LED load having a first forward voltage, and a first switch coupled in series with the first LED load; and a second LED load, having a second forward voltage being different than the first forward voltage; a switched mode power supply comprising a switching element; an inductor; a diode; a set of output pins for coupling to the load; and a capacitor coupled across the set of output pins; wherein the switched mode power supply is arranged to provide a voltage across the set of output pins, wherein the lighting system comprises a further inductor coupled between the one of the output pins and the load.