Monolithic FET Short-Circuit Protection for Solid-State Lighting

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Solution Overview

Problem

Existing solid-state lighting structures (SSLSs) like LEDs and lasers face failures due to high defect concentrations and high current densities, leading to short-circuit paths that cause power supply or driver failures, and current protection methods such as fuses and ESD protection are inadequate in preventing sequential damage and excessive current spikes.

Innovation Solution

Integration of a field-effect transistor (FET) monolithically connected in series with the SSLS, which provides ultrafast switching from a linear to a saturation regime to prevent short-circuit failures, and a thin-film fuse element connected in series with the FET to ensure rapid disconnection of the SSLS upon short-circuit occurrence, eliminating parasitic elements and preventing system damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a fuse is used for short-circuit protection, then the defective device can be disconnected, but the protection process is slow and sequential damage still occurs

Engineering Contradiction:

Improveshort-circuit protection effectivenessVSAvoidprotection response time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The FET is monolithically integrated with the SSLS on the same semiconductor substrate, merging the protection device with the protected device. This integration eliminates parasitic inductances and capacitances between separate components, enabling ultrafast response times that prevent sequential damage while maintaining reliable short-circuit protection.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The FET is pre-configured in a high-impedance state during normal operation, ready to switch immediately upon detecting abnormal conditions. This preliminary positioning allows the protection mechanism to activate instantly when a short-circuit occurs, rather than requiring time for detection and activation sequences.

Inventive Principle:

Principle #10Preliminary action

2Object-affected harmful factors

If ESD protection elements are connected in parallel with SSLS, then voltage spikes can be protected, but short-circuit type failures cannot be prevented

Engineering Contradiction:

Improvevoltage spike protectionVSAvoidshort-circuit protection

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

Instead of connecting protection elements in parallel with the SSLS as in conventional ESD protection, the FET is connected in series with the SSLS. This inverted configuration allows the FET to control current flow through the SSLS by switching between low- and high-impedance states, effectively preventing short-circuit failures while still providing voltage spike protection.

Inventive Principle:

Principle #13The other way round (Inversion)

3Loss of energy

If the FET resistance in linear regime is reduced to minimize degradation, then the SSLS operates better, but the protection capability may be compromised

Engineering Contradiction:

Improveoperational degradationVSAvoidprotection capability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The FET dynamically switches between two operational states: a low-impedance state during normal operation that minimizes degradation and energy loss, and a high-impedance state during protection mode that limits current and prevents damage. This dynamic adaptability allows the system to optimize for different operational requirements.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The FET's impedance parameter is changed based on operational conditions. During normal operation, the FET maintains low resistance to minimize power loss and degradation. Upon detecting a short-circuit, the FET switches to high resistance mode, fundamentally changing the electrical parameters to activate protection while maintaining both operational efficiency and protection capability.

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

The combination of an integrated FET and a thin-film fuse element provides rapid and reliable protection against short-circuit failures, ensuring the SSLS operating current remains below the FET saturation current, preventing system failures and minimizing damage from excessive current.

Implementation Method 1

a field-effect transistor (FET) monolithically connected in series with the SSLS... the FET can be configured to have a saturation current in a saturation regime... the FET will have only a minor degradation of the SSLS under normal operating conditions

Methodology Applied

Scientific EffectField-effect transistor switching:

Implementation Method 2

a thin-film fuse element connected in series with the FET to ensure rapid disconnection of the SSLS upon short-circuit occurrence

Methodology Applied

Scientific EffectFuse melting: Melting

Data Source

PatentUS10002862B2Solid-state lighting structure with integrated short-circuit protection

Publication Date: 2018.06.19 SENSOR ELECTRONIC TECHNOLOGY INC

AI summary

A solid-state light source (SSLS) with an integrated short-circuit protection approach is described. A device can include a SSLS having an n-type semiconductor layer, a p-type semiconductor layer and a light generating structure formed there between. A field-effect transistor (FET) can be monolithically connected in series with the SSLS. The FET can have a saturation current that is greater than the normal operating current of the SSLS and less than a predetermined protection current threshold specified to protect the SSLS and the FET.