Continue to Site

Welcome to

Welcome to our site! is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

over voltage protection circuit

Not open for further replies.


Newbie level 1
Aug 18, 2009
Reaction score
Trophy points
Activity points
overvoltage protection circuit

I need help with a simple over voltage protection ciruit which would cause a 3A fuse to blow if the voltage exceeds 1.35-1.4V. Thaks for your help!

It wouldn't be absolutely precise but you could just use a transistor rated at >3A with a diode between its base and collector and a resistor of about 100K between its base and emitter. Basically, an amplified Zener.

The diode would drop approximately 0.65V and the transistor would need about 0.65V to turn it on.

Alternatively, you could use an SCR directly across your voltage with a diode in line with its gate.


overvoltage protection

Instead of thinking in terms of blowing of fuese, limiting current seems a convenient approach!

over voltage protection

You can use any comparator and a resistor as current sensor. You must add low pass filter between the current sensor and the comparator's input. LPF needs to decrease some disturbance. Output of the comparator can control MOSFET which do what you want: shorts circuit to blow the fuse or turn off the circuit.

protection circuit for relays

Instead you can use a relay to turn off the power (with reset switch if you want)


overvoltage protection circuits

Blowing fuse and switching of relay take finite time as compared to other electronic controls.

under and over voltage switch

ark5230 said:
Blowing fuse and switching of relay take finite time as compared to other electronic controls.
Which (time) is more longer than in electronic circuits. But for topicstarter it may by suitable.

fuse blows overvoltage

two feedback modes... overvoltage or overcurrent...
foldback current limiting can have a very fast response to current spikes, overvoltage sensing responds to fast voltage spikes.
Fuses = medium slow and relays are just the slowest switch around
These conditions are not synonymous and must be treated independently in each feedback loop.
An ideal power supply can deal with both. You'll need feedback loops for both or one or the other, depending on requirements of the system.
What about input voltage and current? Here are 2 more feedback paths you need to optimize & include in the whole feedback loop.
What you are proposing is a simple LIMIT feedback... the circuit shuts down if a given limit is exceeded.
I propose the possibility of control circuits that regulate power in all quadrants. Such is the current state of the art.

I need help on overcurren & overvoltage protection of dc motor

Added after 2 minutes:

I need help on simple over voltage protection ciruit

Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to