Voltage Clamp with Thermal Cutoff for Persistent Overvoltage

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Solution Overview

Problem

Inductively coupled circuits are vulnerable to third-party magnetic fields causing overvoltage conditions, which existing protection circuits may not effectively address, especially when a power source is unavailable.

Innovation Solution

A protection circuit comprising a voltage clamp thermally coupled to a thermal cutoff, which dissipates heat to create an open circuit when an overvoltage condition persists, protecting the circuit without requiring a power source or microprocessor control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a TVS is used to suppress overvoltage conditions, then overvoltage protection is provided, but the TVS may break down and damage the circuit if the overvoltage condition persists too long

Engineering Contradiction:

Improveovervoltage protectionVSAvoidduration of overvoltage tolerance

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

A thermal cutoff device is introduced as an intermediary between the TVS and the circuit. The thermal cutoff acts as a mediator that responds to thermal energy from the TVS during persistent overvoltage conditions, opening the circuit to protect against TVS breakdown while allowing normal TVS operation during transient conditions.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces electrical protection mechanisms (TVS alone) with a thermal-mechanical system. The thermal cutoff device converts thermal energy from the TVS into a mechanical action (opening the circuit), providing protection against persistent overvoltage conditions that electrical alone cannot handle.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If protection circuits like fuses, circuit breakers, temperature sensors and current limiters are used, then circuit protection is provided, but these components require an appropriate power source for operation which may not be available in inductively coupled environments

Engineering Contradiction:

Improvecircuit protectionVSAvoidpower source requirement

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The protection circuit is designed to be self-powered through thermal energy harvesting. The TVS generates thermal energy during overvoltage suppression, and this thermal energy is directly used to power the thermal cutoff device, eliminating the need for an external power source while maintaining continuous protection capability.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent changes the operating parameter from electrical power to thermal energy. By using thermal cutoff instead of electrically-powered protection devices, the system operates in a different energy domain that is self-sufficient in inductively coupled environments where electrical power may be unavailable.

Inventive Principle:

Principle #35Parameter changes

3Loss of energy

If a voltage clamp dissipates energy to a heatsink, then transient energy is dissipated, but this does not provide protection against persistent overvoltage conditions

Engineering Contradiction:

Improvetransient energy dissipationVSAvoidpersistent overvoltage protection

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent converts the harmful thermal energy that would normally be wasted in a heatsink into a useful protective signal. The thermal energy from the voltage clamp is redirected to activate the thermal cutoff device, transforming a waste product into a protective mechanism that safeguards against persistent overvoltage conditions.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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

Effectively protects inductively powered remote devices and other electrical circuits from persistent overvoltage conditions by creating an open circuit before the voltage clamp malfunctions, even when current is low, and can be used in combination with other protection circuitry for enhanced fault protection.

Implementation Method 1

the voltage clamp dissipates a sufficient amount of heat to activate the thermal cutoff creating an open circuit

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

Once a threshold temperature is reached in the thermal cutoff an open circuit is created

Methodology Applied

Scientific EffectMelting: Melting

Data Source

PatentUS8259428B2Input protection circuit

Publication Date: 2012.09.04 PHILIPS IP VENTURES BV

AI summary

A voltage clamp protection circuit to protect against overvoltage conditions where there is insufficient current to blow a fuse. The voltage clamp protection circuit includes a voltage clamp and a thermal cutoff. The voltage clamp clamps any overvoltage to a clamping voltage. If an overvoltage condition persists for too long the voltage clamp dissipates a sufficient amount of heat to activate the thermal cutoff creating an open circuit that protects the rest of the circuit. The voltage clamp protection circuit may be used in combination with a variety of other protection circuits to provide increased protection.