Multi-Channel LED Driver Overheating Protection Circuit

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Solution Overview

Problem

Multi-channel LED arrays face challenges in power consumption and overheating due to variations in bias voltages across LED strings, making it difficult to operate efficiently without increasing manufacturing costs or requiring complex sorting processes.

Innovation Solution

The implementation of switching transistors with error amplifiers and overheating protection circuits that control current flow through LED strings, using resistive elements and switches to manage current and prevent overheating by diverting excess current through a shunt path when high voltage levels are detected.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a single multi-channel LED driver is used to drive multiple LED strings, then manufacturing cost is reduced, but overheating occurs in FETs due to voltage variations across LED strings

Engineering Contradiction:

Improvemanufacturing costVSAvoidoverheating

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

A shunt transistor is introduced as an intermediary component connected in parallel with the FET. This shunt transistor acts as a mediator to divert excess current away from the FET when voltage exceeds a threshold, preventing overheating while allowing the use of a single multi-channel LED driver. The shunt transistor includes a resistor and switch that create an alternative current path, effectively protecting the FET from thermal damage due to voltage variations across different LED strings.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If individual LED drivers are used for each channel to prevent overheating, then overheating is avoided, but manufacturing cost increases

Engineering Contradiction:

ImproveoverheatingVSAvoidmanufacturing cost

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The shunt transistor circuit is designed as a universal protection mechanism that can be applied to any channel within a multi-channel LED driver. Rather than requiring separate dedicated drivers for each channel, the same shunt protection topology can be implemented across all channels of a single multi-channel driver, providing universal overheating protection while maintaining cost-effectiveness through component sharing and circuit reuse.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If LEDs with different forward bias voltages are used in LED strings, then manufacturing flexibility is improved, but power consumption increases due to higher drain voltages in FETs

Engineering Contradiction:

Improvemanufacturing flexibilityVSAvoidpower consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by stationary object

Solution Approach 1:

The circuit dynamically changes the effective resistance parameter by activating the shunt transistor when voltage exceeds a threshold. This parameter change allows the circuit to adapt to different LED forward bias voltages - when voltage is within normal range, the FET operates normally; when voltage increases due to LED variations, the shunt transistor activates to reduce the voltage across the FET, thereby controlling power consumption despite manufacturing flexibility in LED selection.

Inventive Principle:

Principle #35Parameter changes

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 manages current flow and prevents overheating in LED drivers, ensuring stable operation and reducing power consumption across LED strings with varying bias voltages, thereby enhancing the efficiency and reliability of multi-channel LED drivers.

Implementation Method 1

when high voltage levels are detected

Methodology Applied

Scientific EffectVoltage detection:

Implementation Method 2

switching transistors with error amplifiers and overheating protection circuits that control current flow through LED strings

Methodology Applied

Scientific EffectElectrical resistance control: Electrical Resistance

Implementation Method 3

error amplifiers connected to the switching transistors, each of the error amplifiers being configured to control current flowing through the LED string to have a target magnitude

Methodology Applied

Scientific EffectVoltage comparison:

Implementation Method 4

diverting excess current through a shunt path when high voltage levels are detected

Methodology Applied

Scientific EffectCurrent shunting: Shunt

Data Source

PatentUS9961742B2Multi-channel LED driver with overheating protection capabilities

Publication Date: 2018.05.01 MAGNACHIP SEMICON LTD

AI summary

An apparatus to drive a multi-channel light emitting diode (LED) array includes switching transistors connected to LED strings of the multi-channel LED array, error amplifiers connected to the switching transistors, each of the error amplifiers being configured to control current flowing through the LED string to have a target magnitude, and overheating protection circuits connected to the switching transistors, each of the overheating protection circuits being configured to regulate current flowing through a respective switching transistor to have a magnitude less than or equal to the target magnitude.