LED Driver Current-Sense Network for Resistor Fault Detection

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Solution Overview

Problem

Existing LED drivers with current feedback systems face challenges in detecting individual component failures, particularly in the current sense resistor, which can lead to uncontrolled high currents and potential safety hazards.

Innovation Solution

The proposed LED driver incorporates a resistor arrangement with two parallel current sensing branches, each comprising at least two series resistors, and a fault detection unit that processes the voltages at the sensing nodes to detect component failures, allowing the driver to enter a safe mode.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a single current sense resistor is used to sense the current flowing through the LED arrangement, then the device complexity is low and manufacturing is simple, but the reliability is poor because a short-circuited resistor causes loss of control and uncontrolled high currents

Engineering Contradiction:

Improvedetection of component failureVSAvoidresistor arrangement structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The current sense circuit is segmented into two parallel branches, each containing series resistors. This segmentation allows independent monitoring of each branch, enabling detection of component failures in one branch while the other branch continues to provide sensing capability, thus improving reliability without excessive complexity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The fault detection unit continuously monitors the voltages at the sensing nodes of both branches and provides feedback about component status. This feedback mechanism enables real-time detection of short-circuited or open-circuited resistors, allowing the system to maintain reliability through active monitoring

Inventive Principle:

Principle #23Feedback

2Reliability

If two low-side current sense circuits are added to detect faulty sense resistors, then the reliability improves through detection capability, but the loss of energy increases because the LED current flows through both sense resistor combinations

Engineering Contradiction:

Improvedetection of component failureVSAvoidpower losses

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The sensing function is segmented into two parallel branches that share the current sensing load. Each branch contains series resistors that together provide the necessary sensing capability, distributing the energy loss across parallel paths rather than forcing current through sequential sensing stages, thereby reducing total power loss while maintaining detection reliability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The two parallel current sensing branches are merged into a single resistor arrangement that provides both sensing and fault detection functions. By combining the branches in parallel rather than series, the circuit achieves component failure detection while minimizing energy loss through the parallel configuration that reduces the effective resistance seen by the LED current

Inventive Principle:

Principle #5Merging (Combining)

3Ease of manufacture

If multiple small resistors are connected in series or parallel for current sensing, then the ease of manufacture improves and cheap components can be used, but the reliability decreases because individual resistor failures go undetected

Engineering Contradiction:

Improveuse of cheap componentsVSAvoiddetection of component failure

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The resistor network is segmented into distinct series resistor groups within parallel branches, with identifiable sensing nodes at the connections. This segmentation maintains the manufacturing advantage of using multiple small, inexpensive resistors while creating structured monitoring points that enable reliable fault detection through voltage comparison at the sensing nodes

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The fault detection mechanism replaces complex mechanical or invasive testing methods with electrical voltage measurement and comparison at the sensing nodes. This substitution allows automatic detection of resistor failures through simple voltage sensing and processing, maintaining ease of manufacture while significantly improving reliability through electronic monitoring

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 effectively detects component failures without increasing power losses, ensuring safe operation by preventing excessive current delivery and potential hazards such as fire.

Implementation Method 1

a resistor arrangement for sensing the current delivered and providing a feedback signal to the driver unit, wherein the feedback signal comprises a voltage across the resistor arrangement

Methodology Applied

Scientific EffectOhm's Law: Ohm's Law

Data Source

PatentUS12336072B2LED driver and lighting system using the same

Publication Date: 2025.06.17 SIGNIFY HOLDING BV

AI summary

A LED driver having a current sensing resistor arrangement with two parallel current sensing branches, each comprising at least two series resistors connected at a respective sensing node, is provided. The voltages at the two sensing nodes are processed to detect a component failure. The normal current control is based on the voltage across the overall resistor arrangement.