Overvoltage Protection Circuit Clamping Voltage 10V , Withstand Voltage 500V

[Amr Wael]

Hello ,
I would like to design a circuit for overvoltage protection. I want the circuit to limit the power input to 10V Maximum. The maximum input for the circuit could reach 500V. I read about varistors , MOVs and also efuses but I Can't find anything that meets my requirements because most solutions either have large clamping voltage (High voltage solutions) or their clamping voltage is perfect like efuses but they can't withstand high voltages like 500V , Any ideas that could meet my requirements ?
Thank you in advance.

 

[KlausST]

Hi,

You can´t have both: Input 500V and clamp voltage of 10V on a 2-lead-device like a MOV.

--> you need a series impedance that drops the voltage and limits the current. Usually a resistor.

So the MOV will never see the 500V but it sees a limited current. The resistor needs to withstand the pulse voltage, the current peak and the dissipated energy and power.

Klaus

 

[crutschow]

You are clamping the voltage so the problem is not the high voltage, it's the high current that it can generate, depending upon the impedance of the source of the transient.
That's why you may need to add an impedance to the source as KlausST mentioned.

 

[BradtheRad]

It could be practical to turn off the supply entirely when it rises above a certain voltage. A transistor or two can do this.

As supply gets above 10V, start the limiting function via resistive drop. Limit it to 10V.

When it rises to a point where resistive drop generates too much heat or wastes an unacceptable amount of watts, then turn off the transistor completely. It's a similar purpose as a fuse. There are transistors which can withstand 500V.

 

[crutschow]

How long can it stay at 500V?