Over-Voltage Protection Circuit Using MOSFET and Capacitor

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Solution Overview

Problem

Existing over-voltage protection circuits in electronics often require bulky and costly Zener-diodes and resistors, which occupy valuable space and dissipate power, making them undesirable for applications requiring low power consumption and compact designs.

Innovation Solution

An electronic circuit that includes a switching unit, a capacitive component, and a comparing unit to control voltage switching, eliminating the need for Zener-diodes by using a capacitive component to supply voltage when the switching unit is off and preventing over-voltage exposure by switching off when the voltage exceeds a threshold.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If Zener-diodes and resistors are used for over-voltage protection, then the load is protected against over-voltage, but the circuit occupies valuable space and dissipates power

Engineering Contradiction:

Improveover-voltage protectionVSAvoidcircuit board space

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent changes the operating parameters of the MOSFET by using it in a linear region rather than as a simple switch, and employs a capacitor to create a time-delay effect. This allows the protection circuit to respond to over-voltage conditions while avoiding the need for large power-dissipating resistors and space-consuming Zener-diodes, thus reducing circuit board space while maintaining protection reliability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the mechanical/passive protection mechanism of Zener-diodes and resistors with an active electronic control system using a MOSFET and capacitor. This substitution enables more efficient space utilization and reduced power dissipation while achieving the same over-voltage protection function

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If Zener-diodes and resistors are used for over-voltage protection, then the load is protected against over-voltage, but the circuit becomes costly in terms of purchase price

Engineering Contradiction:

Improveover-voltage protectionVSAvoidcircuit cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

By changing the protection mechanism from passive Zener-diode/clamp-based protection to active MOSFET-based protection with capacitive timing, the circuit achieves equivalent or superior protection with lower-cost components, reducing the overall bill of materials cost while maintaining manufacturing simplicity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses a capacitor that can be relatively small and inexpensive compared to high-power Zener-diodes and resistors, while the MOSFET provides durable, reusable protection. This combination reduces component costs while maintaining long-term reliability

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If Zener-diodes and resistors are used for over-voltage protection, then the load is protected against over-voltage, but power is dissipated over the resistor

Engineering Contradiction:

Improveover-voltage protectionVSAvoidpower dissipation

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent changes the protection approach from continuous power dissipation through resistors to intermittent energy storage and release through a capacitor, combined with active MOSFET control. This reduces steady-state power loss while maintaining protection capability, directly addressing the energy efficiency concern

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The capacitor creates a periodic charge-discharge cycle that provides protection only when needed, rather than continuously dissipating power. The MOSFET switches based on voltage conditions, enabling protection action only during over-voltage events, thus minimizing energy loss

Inventive Principle:

Principle #19Periodic action

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 reduces the size and cost of the circuit, while ensuring continuous operation and low power consumption by eliminating the need for Zener-diodes and minimizing power dissipation, thus providing effective over-voltage protection without the drawbacks of traditional circuits.

Implementation Method 1

a capacitive component, connected to the output port and arranged to receive the voltage when the switching unit is switched on and to feed voltage to the output port when the switching unit is switched off

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS9893510B2Electronic circuit for protecting a load against over-voltage

Publication Date: 2018.02.13 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

An electronic circuit for protecting a load against over-voltage is disclosed. The electronic circuit comprises an input port for receiving a voltage and an output port for feeding the voltage to the load. The electronic circuit further comprises a switching unit arranged to switch on and off the voltage from the input port. Moreover, the electronic circuit comprises a capacitive component arranged to receive the voltage when the switching unit is switched on and is otherwise arranged to feed voltage to the output port. Furthermore, the electronic circuit comprises a comparing unit configured to control the switching unit to be switched off when a value at the output port exceeds a first threshold; and to control the switching unit to be switched on when the value is below a second threshold.