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modified 6 years ago

Over-Voltage Protection

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08:02:16

This is a simple Over-Voltage Protection circuit that locks out at around 20.4V. The working is simple. There is a voltage divider at the input which is used to set the lockout voltage. When the input voltage is high enough, the NPN transistor turns on, which inturn turns the PNP transistor on. The PNP transistor pulls the gate of the PMOS high, thus turning it and the load (the lamp) off. There is a small "transition" region between the on and off states (which is bad. The fet gets hot there). I shall try to make it sharper.

Edit: I breadboard-ed the circuit and the lockout is quite sharp.

published 6 years ago

6 years ago

Nice. where uou mention about the point of transition is not gona happen, as when fet get warm, Rds changes, or some ither parameters change, so its not gina stay in that state even if you wanted it to. Only on sim that can happen.. I would use this circuit, nice sharp cut off. I need it to latch off as this is a fliker type, whuch is fine cause it still limits the o/p voltage rising above the limit.

6 years ago

Hmm it's good that it won't stay in that transition region

6 years ago

Maybe to make sharper, need a little submitting...

6 years ago

Submitting? Whats that? I tried this on the breadboard earlier today and it never went into that "transition" region, like you said. It was either hard on or hard off.

6 years ago

Schmitting, a little positive f/b

6 years ago

Actually, it kind of has that Schmitt effect. When I breadboard-ed it, I set a lockout voltage of 10V. The circuit locked out at that voltage, but reset at around 9.85V.

6 years ago

There is a bit even in simulation, if you look carefully,, .

6 years ago

You can avoid this unwanted soft transistion region with some positive feedback. This will cause a hysteresis and the mosfet will always be perfectly on or off. Put 200kOhm from out to the point where you conpare the overvoltage input. Check this http://everycircuit.com/circuit/5640420173021184

6 years ago

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6 years ago

with a rectangle wave shape as parameter you cant test the characteristics of such a circuit. You just overlook the problem but you do not solve it!

6 years ago

original without hysteresris http://everycircuit.com/circuit/4679160757485568 update with hysteresis http://everycircuit.com/circuit/5640420173021184 this is totaly independed how you test it with a triangle ot rectangle, however a rectangle is probably not the wave shape to test the characteristics of such a circuit

6 years ago

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6 years ago

@2ctiby, you clarifies you have absolut no idea why a triangle wave shape is used to demonstrate the characteristics of this circuit.

6 years ago

@interest. Chk this, if relevant, ok, if not relevant, informative,,, i found it interesting........http://sites.music.columbia.edu/cmc/MusicAndComputers/chapter3/03_03.php...................

6 years ago

Btw... I have to agree with @hurz,,, cause he is correct, again.! With a square wave all info would go missing,,, its non linear, etc...etc...

6 years ago

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6 years ago

We missed nothing, the only one who misses the point is @2ctiby as always. Its idiotic to recommend a rectangular source to hide the problem. Just idiotic.

6 years ago

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6 years ago

and again, @2ctiby you are talking nonsense, listen carfully what @PrathikP has said and what he sees as problem. Its a problem, and you cant swipe it away with ling lasting drivels. Dont recommend if you do not know, better listen!

6 years ago

Would i be right in saying thst the step (square), is itself a false hysteresis, . So by using the step you are actually adding poitive feed back , the result given thus is an illusive one.... . !

6 years ago

Would i be right in saying thst the step (square), is itself a false hysteresis, . So by using the step you are actually adding poitive feed back , the result given thus is an illusive one.... . ! I think that's what @hurz is saying,, or is it me who is helusinating!

6 years ago

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6 years ago

The funny thing is, this circuit needs a hysteresis! This is not a option and cant be overlooked by messy methode. Its a must! Without, you are in danger to drive the power mosefet in a linear mode and destroy it. To avoid an operation between saturation and ohmic for a static long situation it needs a feedback and the resulting hysteresis. Another resason is the stability against oscillation! But a rectangular source or any long lasting drivel about "SHARP" switching is @2cent bullshit and caused by his zero knowledge and zero practical background. @2ctiby, listen to recommendations from @ParthikP and dont give recommendations you are not in the position todo this. By far not.

6 years ago

@2ctiby I know that there is "no major problem with gate switching". I just read all of your comments and none of them make sense!

6 years ago

i recommend a hysteresis with a feedback resistor, check this @2cent http://everycircuit.com/circuit/5640420173021184

6 years ago

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6 years ago

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6 years ago

No I independently decided that your comments are nonsense

6 years ago

😛

6 years ago

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6 years ago

@2ctiby, if you have a psu. With say 5 v. O/p, and the ivervoltage of say 6. , if you use a nanual switch, so that the supply voltage can be switched between 5 to 6 volts, the psu. Everytime would go to overvoltsge,. It would never lick at 5.5 volts. Cause of switch action and 2 dtste voltage levels...... Now if you trird to use a pot. To wind the voltage up really slow,,, to find the spot of Metastsbilit, you will find it. SPECIALLY if there is no +ve feed back (ie. No hysterisis)..... You tried to show that gate delay is not causing problems,,,,, so what!? You still need hysterisis... And your methid does not show or test for that..... Yes IF, there wss no hysterisis,, and IF gate delay was a problem,, THEN, dolving the gate delay problem., would not add hysteresis. And the fet. could still be damaged with or without gste delay..... Plus. The squsrr wave you used is impossible, , with zero rise and fall times.. ... check the first 2 or 3 messages......

6 years ago

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6 years ago

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6 years ago

@2ctiby, thanks for telling us what we should and shouldn't do, .,

6 years ago

Oh I'm the one who doesn't understand how the mosfet works! Aren't you the one who forgot about the existance on a saturation region? Aren't you the one who used a square wave input?

6 years ago

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6 years ago

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6 years ago

And thats done with a sawtooth, a fast zero impedance, zeri rise and fall time square wave, might produce the same result, but will not hold any useful info. Specially on sim,. And irl. Not possible anyway....you kerp going on a tangents @cityby.

6 years ago

@2cent are you talking to yourself? Back to the problem, open is this breadboard behaviour, @PrathikP, what you observed with your beardboard stable behaviour is also because of feedback im pretty sure, check this http://everycircuit.com/circuit/5468368782753792

6 years ago

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6 years ago

Interesting @hurz

6 years ago

Oh and @2ctiby, you're the one who's struggling!

6 years ago

Build the circuit for yourself and you'll see the hysteresis. If you're willing to see it, that is.

6 years ago

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6 years ago

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6 years ago

@PrathikP, even there is no hysteresis it does not me it does not function. It does work with and without hysteresis. But only with hysteresis it will work forever, while Mr @2cent still dont understand what a hysteresis is for, let him cry like a baby, thats what he is always doing in this case. First he recommend bullshit, rectangular source to solve a problem, hysteresis is optional, now when i tell you its the only solution he changed his mind and its nonsense, really @2cent you are sick. Dont recommend if you do not know. Learn, whitout hysteresis this circuit can not work forever safely. You are a looser in the past and you will be forever a looser messy @2cent

6 years ago

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6 years ago

Oh @2cent, really, all around you are unknown assholes, just you are the one who knows. Kiani, PrathikP and me have no idea what they do. Even the author of this circuit is an idiot, and you attack him. You are really sick. Stop that, the asshole is you, just you.

6 years ago

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6 years ago

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6 years ago

Hysterisis can not be measured with bulbs,, its a bit more complicated than that 2ctiby.... Hysterisis is essential for over protections,, even if you use s bjt... And the only way for hysterisis is +ve f/b,,,,,

6 years ago

Think anout this,,, a psu. Is equipt with UNDER VOLTAGE protection, eg.. A 5v supply has an under voltsge of 4 volts... Now how would you ever start up the psu. As you switch on its going to go to undervoltage,, csuse it ll see 4 volts before 5, at dtart up..., {nothing to do eith gate delay or calculus) ,, lol.

6 years ago

he still dont get what we called "soft transition". @2cent, this is the linear operating point nobody want, just you see no problem. Input voltages which makes the mosfet in between ohmic and saturation, is that soooo complicated for you to understand. You just jumped over this linear operating point with a rectangular source, ridiculous. The solution, is still a feedback, buildin with an extra resistor or by a weak PSU which little drops in voltage when loaded. All you called "nonsense" Really shut the fuck up!

6 years ago

Umm 10-9.85V = 0.15V is noticable. Do the math. I don't have to blindly take someone's word for it.

6 years ago

I think @2ctiby's just see Fets, , while there is more,, the psu. Supplies expensive equipments and overvoltage protection is to protect the equioments, rather than the psu... Usually a fault in psu. Causes an overvoltage,,, and it might be the very FET failier that causes the protection to kick in.. The FET is sevrving, we arr not serving FETs.

6 years ago

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6 years ago

We can't ask over voltages to be transitions,, obervoltage is a fault condition,,, the best fault is the worse one.

6 years ago

In real life, therr isn't a sepsrate voltage siurce supplying the protecyion circuitary,, it is often the ssme output voltage supplying the voltage for the protection circuit too. Someyimes auxilary supply is used, really, csuse that then needs protection.

6 years ago

Chk this....https://www.analog.com/en/analog-dialogue/articles/curing-comparator-instability-with-hysteresis.html

6 years ago

Kiani, do you really think he can follow an external example if hes not willing to check all given links we have put here? Hes ignorant and do not want to see how this linear operating mosfet gets destroyed if it stays to long in this operating mode. His solution was to jump over this operating point, lol, but we know hes blind

6 years ago

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6 years ago

what is you moron do not understand by this demonstration? http://everycircuit.com/circuit/4782604541493248

6 years ago

"straight edge", you drivel so much nonsense, really look for another hobby you really dont have a talent for electronics. Your only talent is to messup everything. Put rectangular sources to blind all and yourself and avoid problems. You are a clown. Can you at least clarify this and just say it was nonsense to use a rectangular source! No you cant, hmmmm. So what is you still dont understand? We know what this circuit can do for us and we know how we can improve it to not reach linear stable modes we do not want! Formulate a question to the autor. The tipp you gave with the rectangular source we all forgot already. Go for it

6 years ago

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6 years ago

@2ctiby you ve got a blockage. Try having a cup of olive oil every day for say a week.

6 years ago

The world does not have a straight edge, , even a seemingly straight line is curved, causr earth is not flat.

6 years ago

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6 years ago

@2ctiby. Plz. Check this. http://everycircuit.com/circuit/4898615030710272

6 years ago

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6 years ago

,, i am gona make a puzzle post,, to try to make you (and anyone interested) understand this thing about saw tooth... ... Btw,, { insults!? I never }

6 years ago

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6 years ago

It is the original presentation, IDIOT. Do that for yourself and see finaly the issue, and dont jumpover with a rectangular source, LOL

6 years ago

2ctiby. Ok a V/V curve, the point is not spelling, or is it!? Who is turning nasty,, i understand everything you said ABOUT THE FET, . and thank you for the step test to show FET is in order on the knee point. . However this does not solve the problem, ,,, that only +ve f/b and hysterisis would solve... I tried to explain in the original link i posted.. With V/V curve... Everything you say is correct, . You have shown the FET oporates correctly, when the osu. Gets stuck at some overvoltage point, snd things get hot. Everything ok,, just we are stuck at some over the limit voltage indefinitely,, the fet will be fine.. Itd good yo know. But problem doesn't go away hysterisis is required.

6 years ago

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6 years ago

Btw i spent 1l2 hour preparing the post i ssid, but i used done characters, in the description thst the post just vanished ehen i did a save... Can i recovrr it in any way!? Foes anybidy know!? I think it's just lost.. And i am not gona do another one.

6 years ago

@2ctiby as you could see from the V/V curve there is a little hysterisis there.. Already,, adding a little more makes sure consistency,, thats whats done in normal practice in industry.

6 years ago

@2cent, the only one with a big "delay" is you, nobody is talking about DELAY, but you! You started with this DELAY NONSENSE and i told you stop talking nonsense.

6 years ago

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6 years ago

YOU used the word "delay" at first. Nobody else started this bullshit and nobody was thinking about a "delay". Do you understand "YOU"? And you also solved the problem with a rectangular source, how idiotic are you? Can you top that, what is you still dont understand and we have to explain you? You still look unhappy and try to find something which was never there. Sit down and think about what you want from us! We have nothing for you.

6 years ago

@prathk. chk. The modified irf4095., i ve readjusted and is spot on now.....thank fir bringing to my attention.

6 years ago

*irf4905

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