LED Driver Current Balancing via Capacitive Intermediary

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Solution Overview

Problem

Existing LED drivers face challenges in minimizing heating loss, power waste, and current balancing among LED strings, particularly due to characteristic deviations in LED elements, which increase manufacturing costs and reduce efficiency.

Innovation Solution

The proposed LED driver employs a dividing AC driving method with current balancing capacitors and rectifying diodes to ensure equal current distribution across LED strings, reducing resistance-induced heating losses and allowing for precise current control through bipolar transistors and switching converters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If dissipative active elements are added to compensate for voltage drops in LED strings, then current control precision is improved, but heating loss increases

Engineering Contradiction:

Improvecurrent control precisionVSAvoidheating loss

Core Design Contradiction:

Manufacturing precisionVSLoss of energy

Solution Approach 1:

The patent introduces a current balancing capacitor as an intermediary element connected in parallel with each LED string. This capacitor compensates for voltage drops and current imbalances without requiring dissipative active elements, thereby achieving precise current control while minimizing heating loss. The capacitor acts as a non-dissipative compensating element that stores and releases energy to maintain current balance across multiple LED strings.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If dissipative active elements are used for voltage drop compensation, then current balancing among LED strings is improved, but power transmission efficiency deteriorates

Engineering Contradiction:

Improvecurrent balancingVSAvoidpower transmission efficiency

Core Design Contradiction:

Manufacturing precisionVSUse of energy by moving object

Solution Approach 1:

The current balancing capacitor serves as a non-dissipative intermediary that enables current balancing without the power losses associated with resistive elements. By storing electrical energy during periods of low current demand and releasing it during periods of high current demand, the capacitor maintains current balance while preserving power transmission efficiency.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the compensation mechanism from resistive (dissipative) to capacitive (non-dissipative). This parameter change in the type of compensating element fundamentally alters the energy loss characteristics, allowing for effective current balancing without the power transmission efficiency penalties imposed by dissipative active elements.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If multiple LED strings with different forward voltage drops are connected in parallel, then system versatility is improved, but current sharing among strings deteriorates

Engineering Contradiction:

Improvesystem versatilityVSAvoidcurrent sharing

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent segments the parallel LED string system into individually compensated units by connecting a current balancing capacitor in parallel with each LED string. This segmentation allows each string to be independently compensated for its specific forward voltage drop characteristics, enabling diverse LED types and configurations to be combined while maintaining precise current sharing across all strings.

Inventive Principle:

Principle #1Segmentation

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 configuration effectively restricts heating losses, reduces power waste, and achieves current balancing among LED strings, thereby lowering manufacturing costs and enhancing efficiency while maintaining brightness consistency.

Implementation Method 1

at least one or more balancing capacitors positioned on a current path of each LED string for equalizing a current distribution among the LED strings

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

at least one or more rectifying diodes for forming a unidirectional current path via the balancing capacitor to the LED string

Methodology Applied

Scientific EffectRectification: Diode

Implementation Method 3

allowing for precise current control through bipolar transistors and switching converters

Methodology Applied

Scientific EffectTransistor current control:

Data Source

PatentEP2436239B1LED driver

Publication Date: 2014.08.20 LG INNOTEK CO LTD

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AI summary

An LED driver is comprising: at least two LED strings; a rectifier rectifying an alternating current (AC) voltage for supply to the LED strings; at least two balancing capacitors positioned at a current path of each LED string for carrying out a current balancing of the LED strings; at least two path control elements for controlling the current path of each LED string; and a controller controlling the path control elements.