CMOS Adjustable Overvoltage ESD Protection Circuit for LED Arrays

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Solution Overview

Problem

Current LED protection devices are inadequate for providing fast ESD and surge protection, especially when LEDs are connected in series, as they fail to bypass a failed LED effectively and generate excessive heat due to slow turn-on times, limiting their application in fast-switching scenarios like PWM modules.

Innovation Solution

A CMOS-based protection circuit incorporating a plurality of diodes in series, a MOS transistor, and a silicon controlled rectifier (SCR) with adjustable breakdown voltage, allowing for fast current bypass and reduced heat generation when an LED fails, ensuring continued operation of other LEDs in the series.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If Zener diodes are used for LED protection, then ESD and surge protection is provided, but the turn-on time is slow and excessive heat is generated when bypassing failed LEDs

Engineering Contradiction:

ImproveESD and surge protection capabilityVSAvoidturn-on time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent combines a Zener diode with a MOSFET and SCR to create a hybrid protection circuit. The Zener diode provides voltage breakdown protection while the MOSFET provides fast switching capability and the SCR provides low-resistance bypass path, resolving the contradiction between protection reliability and response speed.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The MOSFET acts as an intermediary component that bridges the Zener diode and SCR. When the Zener diode detects overvoltage, it triggers the MOSFET which then activates the SCR to provide the low-resistance bypass path, enabling fast response while maintaining protection capability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If Zener diodes are used in series LED configurations, then overvoltage protection is provided, but excessive heat is generated due to voltage drop and driving current

Engineering Contradiction:

Improveovervoltage protectionVSAvoidheat generation

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The SCR acts as an intermediary that provides a low-resistance bypass path once activated. When overvoltage occurs, the Zener diode triggers the MOSFET which activates the SCR, allowing current to bypass the failed LED with minimal voltage drop and heat generation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The circuit changes the resistance parameter dynamically - the SCR provides high resistance during normal operation and switches to low resistance during bypass mode, reducing heat generation (P=I²R) when protecting failed LEDs in series configurations.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If discrete protection devices are used, then ESD and surge protection is provided, but the slow turn-on time limits application in fast-switching scenarios like PWM modules

Engineering Contradiction:

ImproveESD and surge protectionVSAvoidapplicability to fast-switching applications

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent merges a Zener diode (for protection detection) with a MOSFET (for fast switching) and SCR (for low-resistance bypass) to create a hybrid protection circuit that achieves both reliable protection and fast response time suitable for PWM and other fast-switching LED applications.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent replaces traditional discrete protection devices with a CMOS-based integrated circuit that uses electronic switching (MOSFET) and semiconductor physics (SCR) to achieve microsecond-level response times, substituting slower mechanical or discrete component-based protection systems.

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

The solution provides effective ESD and surge protection with fast turn-on times, preventing damage from overvoltage and allowing other LEDs in a series to function by bypassing a failed LED, while minimizing heat generation and power loss.

Implementation Method 1

a silicon controlled rectifier (SCR) with an anode connected to the input, a base connected to the drain of the transistor, and a cathode connected to the output

Methodology Applied

Scientific EffectSilicon Controlled Rectifier (SCR) switching:

Implementation Method 2

a transistor with a gate connected to a junction between the first resistor and the plurality of diodes and a source connected to the output

Methodology Applied

Scientific EffectMOS transistor operation:

Implementation Method 3

Current LED protection devices may be Zener diodes and other discrete solutions. Usually a Zener diode protects one LED.

Methodology Applied

Scientific EffectZener breakdown:

Data Source

PatentUS9451669B2CMOS adjustable over voltage ESD and surge protection for LED application

Publication Date: 2016.09.20 NEXPERIA BV

AI summary

Various embodiments relate to a light emitting diode protection circuit, including: a plurality of diodes connected in series; an input connected to a first diode of the plurality of diodes; an output; a first resistor connected between the plurality of diodes and the output; a transistor with a gate connected to a junction between the first resistor and the plurality of diodes and a source connected to the output; a second resistor connected between the input and drain of the transistor; and a silicon controlled rectifier (SCR) with an anode connected to the input, a base connected to the drain of the transistor, and a cathode connected to the output.