MOSFET Solid-State Switch With Pre-Check Short-Circuit Detection

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Solution Overview

Problem

Current switching technologies, such as relays and triacs, face limitations when used in high voltage/power circuits with lower voltage/power control signals, including significant heat dissipation, arcing, limited switching cycles, lack of short circuit protection, and inefficiencies in thermostat applications, which lead to electromagnetic noise, increased costs, and reduced reliability.

Innovation Solution

A microprocessor-controlled solid-state switch utilizing MOSFET power switching devices that includes a booster circuit, filter circuit, and a microprocessor to detect short circuits before entering a sustained conductive state, minimizing power dissipation and preventing damage from short circuits through controlled switching.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If relays are used for switching high voltage/power circuits, then the switching function is achieved, but significant heat dissipation occurs adding thermal offset to temperature sensitive controls

Engineering Contradiction:

Improveswitching capabilityVSAvoidheat dissipation

Core Design Contradiction:

PowerVSTemperature

Solution Approach 1:

The patent replaces mechanical relay systems with solid-state MOSFET switching devices. The MOSFETs switch electronically without mechanical moving parts, eliminating contact resistance and arcing while maintaining high voltage switching capability. This substitution dramatically reduces power dissipation and heat generation in thermostat control applications.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Power

If relays are used for switching, then the switching function is achieved, but arcing occurs causing electromagnetic noise and radio frequency interference

Engineering Contradiction:

Improveswitching functionVSAvoidelectromagnetic noise

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

The patent replaces mechanical relay contacts with solid-state MOSFET switches that close electronically without creating arcs. The MOSFETs provide clean electronic switching that eliminates electromagnetic noise and radio frequency interference generated by contact arcing, while maintaining the ability to switch high voltage loads.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Power

If relays are used for switching, then the switching function is achieved, but contact surfaces wear out degrading their ability to form proper contact

Engineering Contradiction:

Improveswitching functionVSAvoidcontact durability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent replaces mechanical relay contacts with solid-state MOSFET devices that have no moving parts or contact surfaces to wear. The MOSFETs provide reliable electronic switching with no degradation over time, eliminating the contact wear problem inherent in mechanical relay systems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Power

If relays are used for switching, then the switching function is achieved, but the number of switching operations is limited to 100K-1M cycles

Engineering Contradiction:

Improveswitching functionVSAvoidswitching lifetime

Core Design Contradiction:

PowerVSDuration of action of stationary object

Solution Approach 1:

The patent replaces mechanical relay switches with solid-state MOSFET devices that have no mechanical wear components. The MOSFETs can perform switching operations indefinitely without degradation, providing essentially unlimited switching lifetime compared to the 100K-1M cycle limit of mechanical relays.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

5Power

If triacs are used for switching, then AC load switching is achieved, but significant power dissipation occurs due to 1-2V voltage drop

Engineering Contradiction:

ImproveAC switching capabilityVSAvoidpower dissipation

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The patent changes the switching device parameters by using MOSFETs with very low on-resistance compared to triac voltage drops. The MOSFETs maintain low voltage drop across a wide range of current levels, significantly reducing power dissipation while maintaining AC load switching capability.

Inventive Principle:

Principle #35Parameter changes

6Power

If relays are used for switching, then the switching function is achieved, but secondary parts such as voltage suppressors are needed adding to cost and space requirements

Engineering Contradiction:

Improveswitching functionVSAvoidcircuit components

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

The patent replaces mechanical relay switching with solid-state MOSFET devices that inherently eliminate voltage spikes and arcing. This substitution removes the need for secondary protective components such as voltage suppressors and snubbers, simplifying the circuit and reducing both component count and PCB space requirements.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS7737762B2Solid-state switch

Publication Date: 2010.06.15 ENERGATE

AI summary

A solid state switch that employs a controller driven input and MOSFET power switching devices is disclosed. The controller can test for a short-circuit on the load side of the MOSFET power switching devices before putting the switch in a sustained conductive state.