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Overvoltage protection circuit or switch control circuit? Which one should I search for my project?

Overvoltage protection circuit or switch control circuit? Which one should I search for my project?

Overvoltage protection circuit or switch control circuit? Which one should I search for my project?

(OP)
Hello everyone,

I have designed a circuit that the input range is 8V to 100V and our input source varies according to spinning speed of a generator.

I am looking for a chip or a circuit that can simply control a switching MOSFET. When input is over 100V, the chip will shut down the MOSFET and no current will go through the main circuit. When input is below 100V, it turn on the switching MOSFET and the main circuit just operate normally.

Can anyone suggest me chips or circuits that I can use or suggest me some "keyword" so that I can narrow down my searching area.

I found some overvoltage protection circuit but they are not 100% what I need.

Hope someone can help me with it. Thank you very much.

RE: Overvoltage protection circuit or switch control circuit? Which one should I search for my project?

How much current shall it handle?
Is there any auxiliary power except the generator voltage?
Does the circuit have to open in microseconds, milliseconds - or a second or two?
What tolerance level do you need? Is 75 - 85 V good enough? Or do you need 79,5 - 80,5 V?

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Overvoltage protection circuit or switch control circuit? Which one should I search for my project?

You want to look-up "voltage comparator". Usually made up with an OP-AMP and some resistors.

You would set one of the comparator inputs up looking at a reference voltage, possibly VCC divided down to something. And, the unknown generator voltage goes to the other comparator input, divided down to the same voltage as the referenced input so the comparator can detect when the unknown has exceeded your preselected tripping (reference voltage).

Note that you want to also have some hysteresis involved with the comparator so understand how you add it with the resistors that are hung around the OP-AMP. You need the hysteresis so that as you get to your trip voltage the switch doesn't get tripped back and forth furiously (oscillates).

Keep in mind too that you want to see filtered generator voltage so noise doesn't trip your switch. Look up "low pass filter" too.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Overvoltage protection circuit or switch control circuit? Which one should I search for my project?

(OP)
Hello Skogsgurra,

1. Usually, the input current is less than 2A but I will say it need to at least handle 4A to 5A.
2. No, only the generator.
3. I think few microseconds should be fine.
4. Yes, I think 75-80V is good enough.

Thank you for help.

RE: Overvoltage protection circuit or switch control circuit? Which one should I search for my project?


Look up the data sheet for the Linear Tech LT4356. There are several variations of this part. Control up to 80V and part is rated for 100V. Datasheet has example circuits operating at 4 amps. Demo boards available at Digikey for around $50.

RE: Overvoltage protection circuit or switch control circuit? Which one should I search for my project?

And, don't miss my post since it came in while you were responding to Skogsgurra's post.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Overvoltage protection circuit or switch control circuit? Which one should I search for my project?

And don't miss Smoked's post! Are you sure about the microseconds response? The fastest active OVP response I have seen in practical use is around 70 us. And that nuisance tripped a lot too often.

What is it that you need to protect? If it is something that heats, then seconds will work. If it is something that just breaks down at >80 V, then I would use a passive protection. Perhaps combined with something that trips and disconnects after a few hundred milliseconds.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Overvoltage protection circuit or switch control circuit? Which one should I search for my project?

(OP)
Hello guys,

Thank you for your suggestions!!!

@itsmoked I'm trying to build one circuit base on your response. I am still a rookie but I will try my best! Thank you! I will try to update later.

@Skogsgurra Actually, I am not sure about it. I just want this circuit can shut down a switch MOSFET immediately so that when the input is over 100V, it won't damage our main circuit. Probably it need a faster response time.

@Comcokid I checked this one before but I need more than 100V application. I don't think LT4356 match my project. Thank you anyway~

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