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What if my load is a battery? Will PMOSFET also protect me from plugging the charger to the battery the wrong way? Or will the voltage from battery keep PMOSFET open and everything will go in flames?
@@CaptainDangeax Aparently when the load can provide its own voltage, one mosfet is not enuough. You need at least two and two resistors to avoid blowing fuses or something more valuable. www.analog.com/media/en/technical-documentation/application-notes/AN-171_AN-1568.pdf
@@niceshotapps1233 My point is why would you use such a protection on a battery charger ? Of course it's perfectly fit for any electronic appliance with external power supply, but for a battery charger, I don't see the point as I already wrote
2023, 11 years on and this still helps a lot of us. Just dropping this comment to wish you well, and hope that you're living your best live. Warm regards from Manila, PH
Ok, I’m here. Sorry for the 4 year delay but please understand there’s a major backlog for TH-cam commenters requesting awards. With that being said... Hear Ye Hear Ye! We gather here today to recognize Afrotechmods for his stellar video tutorials that have gone above and beyond in helping others. His no bullshit approach combined with clear and concise dialogue alone was far more than his competition could come up with yet even that wasn’t enough for Afrotechmods. In a game changing manner, Afrotechmods set the bar higher than Willie Nelson at Snoop Doggs pool party by making a video without a single fucking digression, a feat many TH-cam viewers believed to be impossible. We Salute you, Afrotechmods!
Props to you for making electronics understandable to the rookie. Years ago, I took an electronics class at the college. First off, I didn't understand jack about what was really going on.... with a few exceptions. But I knew how to calculate stuff, and if I built the schematic right, it worked. Thus I got an A. Boy did I fool them. Later in life I'm exploring electronics again, and I'm pleased that there's lots of good videos that explain this stuff in a less technical fashion... so a rookie can get it.
or use a diode on the + and - backwards so that it will short circuit ur power supply if connected backwards for dirt cheap and effective reverse polarity protection :)
Yours is a much better video for newbies like me, than the other popular channels which actually just zoom past the descriptions. Your formula and circuit descriptions were very lucid. Thank u..
This was interesting, I was a bit surprised that there was no mention of using a bridge rectifier. Basically, it forward both wires to the positive with the one that's actually positive and both wires to the negative with the one that's actually being the negative being the only one that goes through. The original NES console used a transformer to drop from household current down to 9v of AC and then used a rectifier inside ether unit to ensure proper polarity. The result is that you can plug in any 9v power source that fits the barrel jack and it just works. It doesn't matter what polarity or whether it's DC or AC.
In the past, mosfets and co. was black magic for me. When I saw your tutorial videos, I understood it + the datasheets of mosfets make sense now. I really appreciate your time spending such good clips and hope to see more of them.
This has made everything so clear, I have been trying to figure out p-channel mosfets for months now in a circuit simulator circuit simulator and getting really confused as to why things were not working the way I thought they would, and that's all because it doesn't show the ''parasitic diode'' in the mosfet.
Very intuitive explanation. You make excellent videos!! Please make more! One of the channels on TH-cam that does make sense and is very educational down to the point you want. Lots of good examples and case scenarios.
Am I glad I stumbled on this tutorial! What a great trick. I never thought about that one. Furthermore, one could do the same with an N type MOSFET by just connecting the drain on the minus side of the power source.
sony10 , yes , I agree that at first glance, the circuit appear quite weird. But when you look closely pay attention to the polarity of a P channel Gate compare to Source. Keep in mind that a MOSFET is a variable resistor ( at least when utilized at low voltage ) . This means that , when ON, (short) , you can feed current both polarities, it still will act as a short circuit. This is why it appear weird when you look at a circuit that show a P channel connected as if it was a N channel. In this circuit the PMOS is utilized in reverse polarity. It need to be this way because of the internal inevitable substrate intrinsic diode that would be turned ON if you were to use an N channel and made a mistake of reversing polarity. You don't want any current circulating if in reverse battery connection. Hence, wether using a P or NMOS you want the internal diode in the direction of the current flow. Most circuits utilize a MOSFET configuration with current being blocked by the internal diode. In this circuit you want it configured such that when the battery polarity is correct the current would flow through the internal diode (if the gate was not energized) because in case of reverse battery polarity ( an undesirable error ) you certainly do not want any current flowing. So, you Then have to connect the PMOS in reverse, which is totally allowed according a MOSFET specification sheet. Once the battery is connected properly the internal diode will bring the Source to a higher potential then the Gate ( even if the Drain is of higher potential, it's not prohibited) you now have a Gate that could be connected to a voltage potential lower than the Source ( a condition to turn ON the PMOS) . Once the Gate is put to a lower potential it turns ON the PMOS and the voltage lost in the internal diode becomes almost zero because you now have a PMOS turned ON ( a short circuit ). Hope that make any sense to you. At least, that is how I see it.
sony10 , the short version. A MOSFET can be utilized both polarities. As long as the Gate is at lower voltage then the Source you have a ON (short) MOSFET , which is what you want here in this circuit. D higher voltage than S is totally allowed if you do not exceed the forward internal diode maximum current mentioned in the specification sheet of your device.
@mediaguardian Above -2V, (i.e. -1V, 0V, +2V etc.) the mosfet is in cutoff mode ("off"). Between -2V and -4V (specified min and max) the behaviour could easily vary from batch to batch and you could end up in the linear region where the Rds is several ohms to several kilohms. Then -4V or less (-5V, -6V etc) you enter saturation mode ("on") with lower resistance as you approach -25V. So in a switching application the designer knows to stay well beyond the -2...-4V range
Professional Solution: 1)Use of data-sheet parameters to support design. 2)Didactic video that explains clear and detailed. 3)focus only in topic. Great Tutorial.
Very nice introduction to reverse battery protection technics. You also could have mentioned the use of NMOS (and its associated charge-pump circuit) if you are in the case of very high drain current (NMOS tends to have better Rdson characteristics than PMOS). But this method requires more complex circuitry of course ...
Excellent explanation! There could be just one minor improvement - the contradiction proves the transistor cannot *stay* ON but it does *not* prove it wouldn't start to conduct from the initial state when it is still OFF. In other words, without proving the process of conducting could never *start* we cannot be sure if there aren't oscillations. Because, *if* in the initial moment the transistor was starting to conduct, we proved only it will turn OFF once after it *already* was turned ON. If the tranistor would then (when it is OFF) be able to start conducting (again) the process would repeat again and again. I am aware these conditional sentences are not grammatically 100% correct but I hope it could be understood what I wanted to say.
If the battery is connected in reverse as in 3:21 then the Drain of PFET is below ground, then the Source pin doesn't have much chance of ever going above ground so PFET should never turn on.
Good stuff. I've seen a few of your videos like this one. You don't overload them with information the average hobbyist doesn't need, but you don't leave it so vague that a part timer might still get it wrong.
Handy to know tip! In certain cases where you're not bothered about power efficiency, just use a bridge rectifier then you can connect your power leads which ever way you like and it'll always work!
Thanks for the video. But when choosing the right MOSFET for some application, I think that the choice must also take in consideration the maximum current allowed through the transistor.
Honestly, the only thing I really understood was at the very very end when u said "You are now hereby granted with powers of reverse voltage protection!" 😬👍
Please, please make more vids! I have learnt more from you than any other. You have ultimate teachers talent. Use it to fulfill child's dream of better world.
I can't for the life of me figure out how I only now discovered your channel... TH-cam recommendations are lacking! I've been watching EEVBlog and W2AEW for years, but only found your channel recently.
1. schematic called "ideal diode". 2. n-mosfet better then p-mosfet (cuz Ron is smaller). it have simmetrical schematic but inserted to ground wire . 3. nice video :) best regards
Use a charge pump on the gate. Really simple to implement because its not drawing any current. You can buy a small IC that provides the voltage you need. To protect the charge pump IC you can just implement pMOS or a simple diode on its VCC terminal. Since it draws current in the uA range, the losses are negligible. The losses in implementing the charge pump to have a high side nMOS is usually much lower than using a pMOS
@@ericcartmann true but look at the datasheet again, it's spec'd at 0.026 ohms @ ~24 amps/10 volts, ( heat sunk to 25 deg C of course ) in any case at 2.0 amps it's much much less. personally i prefer Geranium diodes over Si... lower Voltage drop . . . & i have a ton of those laying around in metal cases.
@@robozstarrr8930 The problem with those metal cases is they are made of zinc, and zinc whiskers. Most of them have already shorted themselves out and they are no longer manufactured.
Be _very_ careful about that on a complex system (with multiple boards, for example) because you may short the "Protected" Ground with the real ground over multiple boards and fry them all T.T
If you think of protective fet as of part of the battery, it doesn't make any difference, is it pfet at positive battery terminal, or a nfet at negative one. In other words, just assume your ground and positive rail after fet, and never think of reaching battery's terminals, and you are good. So I would think of using nfet at bottom always, they often go under 10 mOhm of rds on. Also, nfet is very convenient when you want to control its gate with a MCU for soft on-off feature.
in a book i am reading, we just got from diodes to transistors and semitransistors and so i am glad to see this video from you. you can be a very great teacher for me to learn from
Thank you. You explained this really well! I like how you don't gloss over any of the important details and how you work up from a simple solution to a more complex one and explain all the hows and whys. Really excellent video!!
I know this works, but one thing is bugging me: if you are using a PMOS, the normal current flow should be from source to drain, and not the other way around. This should be OK if you had the symmetrical component (like JFET), but this is not the case. Can you explain this a bit?
Milan Lukic In fact, for PMOS, if Vds>0.7 or so, it just turn on and act as a diode (no matter what the voltage is on the Gate). you can get this info. from it's symbol...
Milan Lukic MOSFETs generally work on the fact that a channel is created between drain and source when the gate charge attracts charges into the channel, reversing its behavior. When a channel is created, it doesn't matter which way the electrons flow in it.
Milan, you’re right. The Drain-Source should be swaped. MOSFET has a internal diode that points from source to drain in N channel devices and drain to source in P channel devices. Therefore in a PMOS current flows from Source to drain not the other way around.
Thank you for this video. I have watched numerous videos all talking about reverse polarity and showing you a generic circuit. But very few bother to comment on how to choose your parts. Again, thank you.
This one is really good for me as I have just finished making my 0v to 27 v regulated discreet power supply with variable current . The lecture is very clear and precise.Very good video
I have the best and simpliest solution to this( without any wasted energy) Get yourself a some round connector, that you cant plug in reversed ! It's drunk proof, dumb proof...... :D
That's funny. That is until I started to really thinking about it, it's not such a bad idea after all. If we made the whole world with drunk proof electricity then no more Boo Boo's with all of that going on No More, No More, as the Raven said, LOL.
Think of a little guy inside with a voltmeter and a rheostat. The voltmeter measures the voltage between the gate and source. As that voltage increases, he turns the resistance down on the rheostat. It's the same as the model for a BJT, except that the little guy there has an ammeter instead of a voltmeter.
@CoolDudeClem I implied several times in the video that if Vgs is 0V the FET would be off. It needs -4V or less to turn on. The circuit at the end of the video with the zener diode will clamp a large gate voltage down to the zener voltage.
@Afrotechmods that is exactly what I saw in the sim, and would expect. Thanks for the videos. Your time and effort making these videos are greatly appreciated. Thank you.
@colt4547 You absolutely can. But the downside is that you introduce a few milliohms of resistance on your ground rail, which may or may not be a problem depending on what you are doing.
I love coming to your channel and videos to "wrap up" my understanding of various topics. I'm newbie and just getting back into using p-channel mosfets. I had an ok understanding of how to read the p-channel data sheet to choose the correct transistor for my app however after listening to this it makes complete sense - I wish all my teachers were like you "back in the day" (or at least I wish they had youtube when I was in college lol) - thank you!
@LiKBeAsT I've thought about doing such a video. There are just too many things to make videos on... Anyways when we are not talking about ground meaning the earth's ground, ground can be anywhere you want in the circuit. It is a reference point. You can choose the ground node to be anywhere you want and do your design & analysis based around that. However, using certain nodes makes things easier than others. Most of the time it's easiest if GND = battery's -ve terminal.
@LiKBeAsT "So when it's not ... choose which ever one we want (without being too supid:P) ?" Yes. The mistake you are making with the battery is that you are viewing the + terminal as an absolute value of +12V. Voltage is always relative, between two points. The batt's + terminals is 12 volts higher than the batt's -ve terminal. So if we declare GND to be at the batt's + terminal, the -ve terminal has to be at 12 volts less than that.
THANK YOU. CLEAR. EXACTLY WHAT WE WERE TALKING ABOUT AT BREAKFAST; AND YOU'VE ALREADY DONE IT !!! I WAS USING THIS IN SOLAR PANEL DESIGN ELIMINATING DIODE LOSS. LOOKING AT N CHANNEL FOR LOWER RDSS. NICE TUTORIAL, THANKS AGAIN.
love ur sense of humor. great vid too! I love to blow things up. ran 5v through a 3v led, lens cap got hot, exploded sending the cap through the ceiling tile AUSOME!!!!!!
In p-channel.. load is always connected to source.. when gate is pulled down to ground, the current flows from source and passes through the drain into the load. Mosfet is bi directional. Your video is trying to tell the opposite way if I am not wrong. Your explanation is pretty good. @ 2:39 if the mosfet is ON , then body diode turns OFF. @ 2:39 both are conducting which is a big flaw.. Body diode is ON when the FET is OFF... I am just trying to explain it. Your videos are awesome...
Hello @Afrotechmods! At minute 3:00 in the video you subtracted 11 Volts off of 0 Volts. Could you please explain why you did it in this order and not the other way around (11V - 0V = 11V)?
That's just how you calculate the voltage between two points. The formula is at the bottom of the screen. More generally, V12 = V1 - V2. And this is of course always referenced to whatever the ground/common node in the circuit is.
Awesome explanation, we do this at work but many an engineer just take it as tribal knowledge, it is refreshing to have the principal explained as the teacher would explain it to the pupil.
There is also a way to connect a diode in parallel with the load, but this will damage the power supply. The method shown is a well-thought-out practical circuit.
Thank you very much, someone FINALLY!!! did a video on this. I've been looking for this particular answer for a week or two by now. First one was the SINE WAVE-MADE PURE was my first & of coarse the second one fell right into order with what I needed. I subscribed so hopefully I'll get any new ones on these subjects. Thanks again, Tom.
To complete the analysis, you can show that the power lost by the 100Kῼ and diode is far less than the 1.7W across a forward-biased diode; power dissipated by 10V across a 100Kῼ = 0.4 mW? That's around a 3 decade improvement! Excellent by any standard.But at that voltage, the 100Kῼ only allows 200uAmps through the Zener. That might not constitute a high enough keep-alive current for the diode to work. At any rate, that was nicely done. Thanks for the crystal clear sequence of analysis.
This limits Zener current. Máximun R value is calculated using Iz (reverse current when Vz is reached, typically a very small value). In this circuit: R = (30 - 10) / Iz As R= 100k, Iz must be 0.2mA In my opinion, you can use this 0.2mA value without fear of making a mistake, but you can take 1mA just to be sure
Your videos are awesome. I was watching a few of them trying to connect the dots for a simple reverse voltage protection circuit that doesn't have a big forward drop (I'm splitting the output from a computer power supply to try and power a few ultra-low-power boards from one). Then I saw this, which makes those leaps for me. AWESOME. Also, if you think there's any huge red flags I should watch out for in my project, please say something. :) Otherwise, keep making videos for the rest of time.
Great video! I literally just ordered some assembled PCBs with diode protection just this morning before watching this. should have implemented the mosfets instead doh! thanks for the great explanation
@DracoXul You could do that, but then you get double the voltage drop and therefore twice the heat in all situations. Personally I think it's better to have something that just doesn't work when you plug things in backwards, then you can just flip the battery around. 99% of the time you are going to plug it in the right way around anyway.
Excellent. Just what I need. I'd heard of doing this but didn't know which FET to use or how to connect it. I previously used a reverse connected diode, by accident I connected the battery in reverse one day, sure it passed a lot of current, blew the fuse and saved my circuit but it blew the end off the diode. Another diode needed. This sounds ideal.
You can do the same thing by using N-channel mosfet, and it will be more efficient. But you have to connect the mosfet to the low side. If you don't have problem with placing some circuit element between the circuit ground and outside ground, I suggest using N-channel mosfet.
@@robotboy3525 N-channel uses electrons as charge carrier, while P-channel uses holes. If you go to any semiconductor part seller (e.g.; Digikey, Farnell, Mouser, etc) and enter the same mosfet parameters (Rdson, Vdsmax, package type, Ciss, ect) as filter, you will see that a similar N-channel mosfet is very cheaper than the equivalent P-channel one.
Holes vs Carriers ??? So by using electrons as carriers how does that make it more efficient?? Also when you say cheaper, are you referring to the pricing ?? Based what I learned from an electrical engineer, n-channel is much faster since it paves the path to ground but it is the most dangerous. Pretty much all reverse voltage polarity integrated circuits on the market uses p-channel. Thus I think this would be the case because safety comes first.
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thank you for this very usefull video. I know what to do with all those useless mosfets I got on dead PC motherboards
What if my load is a battery? Will PMOSFET also protect me from plugging the charger to the battery the wrong way? Or will the voltage from battery keep PMOSFET open and everything will go in flames?
@@niceshotapps1233 The charger already provides a diode bridge rectifier and a fuse. Plug it the wrong way a the fuse will simply blow
@@CaptainDangeax Aparently when the load can provide its own voltage, one mosfet is not enuough. You need at least two and two resistors to avoid blowing fuses or something more valuable. www.analog.com/media/en/technical-documentation/application-notes/AN-171_AN-1568.pdf
@@niceshotapps1233 My point is why would you use such a protection on a battery charger ? Of course it's perfectly fit for any electronic appliance with external power supply, but for a battery charger, I don't see the point as I already wrote
2023, 11 years on and this still helps a lot of us. Just dropping this comment to wish you well, and hope that you're living your best live. Warm regards from Manila, PH
Same here, only 2024.
This series is excellent. Easily the best electronics tutorials on TH-cam that I've run across. Someone please give this man an award.
Ok, I’m here. Sorry for the 4 year delay but please understand there’s a major backlog for TH-cam commenters requesting awards. With that being said...
Hear Ye Hear Ye! We gather here today to recognize Afrotechmods for his stellar video tutorials that have gone above and beyond in helping others. His no bullshit approach combined with clear and concise dialogue alone was far more than his competition could come up with yet even that wasn’t enough for Afrotechmods. In a game changing manner, Afrotechmods set the bar higher than Willie Nelson at Snoop Doggs pool party by making a video without a single fucking digression, a feat many TH-cam viewers believed to be impossible. We Salute you, Afrotechmods!
True
Why dont YOU give him an award?? Allways the others should do it...
Here's the award : 🏅🏆
Props to you for making electronics understandable to the rookie. Years ago, I took an electronics class at the college. First off, I didn't understand jack about what was really going on.... with a few exceptions. But I knew how to calculate stuff, and if I built the schematic right, it worked. Thus I got an A. Boy did I fool them. Later in life I'm exploring electronics again, and I'm pleased that there's lots of good videos that explain this stuff in a less technical fashion... so a rookie can get it.
Just wanted to say you make the best tutorials !!!!!!
+George Kot Thanks!
Agreed!
or use a diode on the + and - backwards so that it will short circuit ur power supply if connected backwards for dirt cheap and effective reverse polarity protection :)
If your 'power supply' is a non protected lithium polymer battery, that's not going to be pretty
With a proper rated fuse or polyfuse this could work
Yours is a much better video for newbies like me, than the other popular channels which actually just zoom past the descriptions. Your formula and circuit descriptions were very lucid. Thank u..
This was interesting, I was a bit surprised that there was no mention of using a bridge rectifier. Basically, it forward both wires to the positive with the one that's actually positive and both wires to the negative with the one that's actually being the negative being the only one that goes through. The original NES console used a transformer to drop from household current down to 9v of AC and then used a rectifier inside ether unit to ensure proper polarity. The result is that you can plug in any 9v power source that fits the barrel jack and it just works. It doesn't matter what polarity or whether it's DC or AC.
In the past, mosfets and co. was black magic for me. When I saw your tutorial videos, I understood it + the datasheets of mosfets make sense now.
I really appreciate your time spending such good clips and hope to see more of them.
I've been doing electronics for 50 odd years and how that simple trick evaded me I'll never know. Well presented.
lol
This has made everything so clear, I have been trying to figure out p-channel mosfets for months now in a circuit simulator circuit simulator and getting really confused as to why things were not working the way I thought they would, and that's all because it doesn't show the ''parasitic diode'' in the mosfet.
Very intuitive explanation. You make excellent videos!! Please make more! One of the channels on TH-cam that does make sense and is very educational down to the point you want. Lots of good examples and case scenarios.
I am impressed by the clarity in your English and pronunciation.
Am I glad I stumbled on this tutorial! What a great trick. I never thought about that one. Furthermore, one could do the same with an N type MOSFET by just connecting the drain on the minus side of the power source.
Hey man. The circuit in this video. Why does D and S revesed?
Usually, PMosfet, S to + and D to load!!! This is crazy
Plz help 😣
sony10 , yes , I agree that at first glance, the circuit appear quite weird. But when you look closely pay attention to the polarity of a P channel Gate compare to Source. Keep in mind that a MOSFET is a variable resistor ( at least when utilized at low voltage ) . This means that , when ON, (short) , you can feed current both polarities, it still will act as a short circuit. This is why it appear weird when you look at a circuit that show a P channel connected as if it was a N channel. In this circuit the PMOS is utilized in reverse polarity. It need to be this way because of the internal inevitable substrate intrinsic diode that would be turned ON if you were to use an N channel and made a mistake of reversing polarity. You don't want any current circulating if in reverse battery connection. Hence, wether using a P or NMOS you want the internal diode in the direction of the current flow. Most circuits utilize a MOSFET configuration with current being blocked by the internal diode. In this circuit you want it configured such that when the battery polarity is correct the current would flow through the internal diode (if the gate was not energized) because in case of reverse battery polarity ( an undesirable error ) you certainly do not want any current flowing. So, you Then have to connect the PMOS in reverse, which is totally allowed according a MOSFET specification sheet. Once the battery is connected properly the internal diode will bring the Source to a higher potential then the Gate ( even if the Drain is of higher potential, it's not prohibited) you now have a Gate that could be connected to a voltage potential lower than the Source ( a condition to turn ON the PMOS) . Once the Gate is put to a lower potential it turns ON the PMOS and the voltage lost in the internal diode becomes almost zero because you now have a PMOS turned ON ( a short circuit ). Hope that make any sense to you. At least, that is how I see it.
sony10 , the short version. A MOSFET can be utilized both polarities. As long as the Gate is at lower voltage then the Source you have a ON (short) MOSFET , which is what you want here in this circuit. D higher voltage than S is totally allowed if you do not exceed the forward internal diode maximum current mentioned in the specification sheet of your device.
@@jimviau327 tks alot
And tks again!!!
Im thinking.... This one is crazy
@@jimviau327 now I can die in peace ✌️
Great video, no god-awful background music (which is always too loud), or sound effects. Thanks Afrotech, you do good work.
Yeah Bob you're right for once somebody mentioned something about the crappy generic music that people put on these electronic videos..thanks :)
@mediaguardian Above -2V, (i.e. -1V, 0V, +2V etc.) the mosfet is in cutoff mode ("off"). Between -2V and -4V (specified min and max) the behaviour could easily vary from batch to batch and you could end up in the linear region where the Rds is several ohms to several kilohms. Then -4V or less (-5V, -6V etc) you enter saturation mode ("on") with lower resistance as you approach -25V. So in a switching application the designer knows to stay well beyond the -2...-4V range
Professional Solution: 1)Use of data-sheet parameters to support design. 2)Didactic video that explains clear and detailed. 3)focus only in topic. Great Tutorial.
Just as your other videos, a clear and concise explanation of an electronics concept. Thank you.
You're born to be a teacher! The explanation is easy to follow
Very nice introduction to reverse battery protection technics. You also could have mentioned the use of NMOS (and its associated charge-pump circuit) if you are in the case of very high drain current (NMOS tends to have better Rdson characteristics than PMOS). But this method requires more complex circuitry of course ...
If your battery is isolated from 0V a N MOSFET on the negative works just as well😊
The world needs tons of people like you Sir....!
very well detailed explained...!
Thanks..!
Excellent explanation! There could be just one minor improvement - the contradiction proves the transistor cannot *stay* ON but it does *not* prove it wouldn't start to conduct from the initial state when it is still OFF. In other words, without proving the process of conducting could never *start* we cannot be sure if there aren't oscillations. Because, *if* in the initial moment the transistor was starting to conduct, we proved only it will turn OFF once after it *already* was turned ON. If the tranistor would then (when it is OFF) be able to start conducting (again) the process would repeat again and again. I am aware these conditional sentences are not grammatically 100% correct but I hope it could be understood what I wanted to say.
If the battery is connected in reverse as in 3:21 then the Drain of PFET is below ground, then the Source pin doesn't have much chance of ever going above ground so PFET should never turn on.
Good stuff. I've seen a few of your videos like this one. You don't overload them with information the average hobbyist doesn't need, but you don't leave it so vague that a part timer might still get it wrong.
Wow. It is something awesome and cool. Great work uploaded.
Handy to know tip! In certain cases where you're not bothered about power efficiency, just use a bridge rectifier then you can connect your power leads which ever way you like and it'll always work!
Please continue to make videos!
This channel is a Carrier and by extension life saver,tons of credit to you Boss.
Thanks for the video. But when choosing the right MOSFET for some application, I think that the choice must also take in consideration the maximum current allowed through the transistor.
You are simply an AWSOME teacher. Fantastic work! Thank You.
Honestly, the only thing I really understood was at the very very end when u said "You are now hereby granted with powers of reverse voltage protection!" 😬👍
Please, please make more vids! I have learnt more from you than any other. You have ultimate teachers talent. Use it to fulfill child's dream of better world.
Thanks man, I always learn something watching your vids
I can't for the life of me figure out how I only now discovered your channel... TH-cam recommendations are lacking! I've been watching EEVBlog and W2AEW for years, but only found your channel recently.
amazing tutorial. thank you very much for the fine explanation. thoroughly clear
I'm just starting to study electronics and these are some of the most fun vids on YT.
1. schematic called "ideal diode".
2. n-mosfet better then p-mosfet (cuz Ron is smaller). it have simmetrical schematic but inserted to ground wire .
3. nice video :) best regards
+nRADRUS 2. True, but we want a common ground, if somehow possible.
lg, couka
Use a charge pump on the gate. Really simple to implement because its not drawing any current. You can buy a small IC that provides the voltage you need.
To protect the charge pump IC you can just implement pMOS or a simple diode on its VCC terminal. Since it draws current in the uA range, the losses are negligible.
The losses in implementing the charge pump to have a high side nMOS is usually much lower than using a pMOS
@@ericcartmann true but look at the datasheet again, it's spec'd at 0.026 ohms @ ~24 amps/10 volts, ( heat sunk to 25 deg C of course ) in any case at 2.0 amps it's much much less. personally i prefer Geranium diodes over Si... lower Voltage drop . . . & i have a ton of those laying around in metal cases.
@@robozstarrr8930 The problem with those metal cases is they are made of zinc, and zinc whiskers. Most of them have already shorted themselves out and they are no longer manufactured.
Be _very_ careful about that on a complex system (with multiple boards, for example) because you may short the "Protected" Ground with the real ground over multiple boards and fry them all T.T
Afrotechmods come back, I miss how informative and easy to follow your videos are for learning. :(
Great video. It's much easier/cheaper to find low Rds on n-channel mosfet than p-channel. Once you get to
If you think of protective fet as of part of the battery, it doesn't make any difference, is it pfet at positive battery terminal, or a nfet at negative one. In other words, just assume your ground and positive rail after fet, and never think of reaching battery's terminals, and you are good.
So I would think of using nfet at bottom always, they often go under 10 mOhm of rds on. Also, nfet is very convenient when you want to control its gate with a MCU for soft on-off feature.
in a book i am reading, we just got from diodes to transistors and semitransistors and so i am glad to see this video from you. you can be a very great teacher for me to learn from
"...and you can be as drunk and irresponsible as you want." 😂
Thank you. You explained this really well! I like how you don't gloss over any of the important details and how you work up from a simple solution to a more complex one and explain all the hows and whys. Really excellent video!!
I know this works, but one thing is bugging me: if you are using a PMOS, the normal current flow should be from source to drain, and not the other way around. This should be OK if you had the symmetrical component (like JFET), but this is not the case. Can you explain this a bit?
Milan Lukic In fact, for PMOS, if Vds>0.7 or so, it just turn on and act as a diode (no matter what the voltage is on the Gate).
you can get this info. from it's symbol...
Milan Lukic MOSFETs generally work on the fact that a channel is created between drain and source when the gate charge attracts charges into the channel, reversing its behavior. When a channel is created, it doesn't matter which way the electrons flow in it.
Milan, you’re right. The Drain-Source should be swaped. MOSFET has a internal diode that points from source to drain in N channel devices and drain to source in P channel devices. Therefore in a PMOS current flows from Source to drain not the other way around.
ElectroBOOM Medhi! You are one of my heroes
@@SakarPudasaini10 you are a godsend
Thank you for this video. I have watched numerous videos all talking about reverse polarity and showing you a generic circuit. But very few bother to comment on how to choose your parts.
Again, thank you.
Thanks for the great video, now I can make a more efficient killing machine. :-)
It's Dec 2024, and this video is still helpful even though I know the circuit but helps to clear confusion when working with complex circuits.
"lol, typo" ha nice ^^
Still there
Thanks for taking the extra time and effort to make your videos concise and succinct.
Great I am a master at this...now I just have to learn electricity in physics...lolz
This one is really good for me as I have just finished making my 0v to 27 v regulated discreet power supply with variable current . The lecture is very clear and precise.Very good video
Maxx Smaxx the zip
I have the best and simpliest solution to this( without any wasted energy) Get yourself a some round connector, that you cant plug in reversed ! It's drunk proof, dumb proof...... :D
That's funny. That is until I started to really thinking about it, it's not such a bad idea after all. If we made the whole world with drunk proof electricity then no more Boo Boo's with all of that going on No More, No More, as the Raven said, LOL.
Poka yoke, always best indeed. Thought a protection can't do any harm...
Until the drunk installs the batteries backwards.
what a gift to sell knowledge to others ! - world needs such teachers
Mosfets are soo strange
Think of a little guy inside with a voltmeter and a rheostat. The voltmeter measures the voltage between the gate and source. As that voltage increases, he turns the resistance down on the rheostat. It's the same as the model for a BJT, except that the little guy there has an ammeter instead of a voltmeter.
@CoolDudeClem I implied several times in the video that if Vgs is 0V the FET would be off. It needs -4V or less to turn on. The circuit at the end of the video with the zener diode will clamp a large gate voltage down to the zener voltage.
One of the best videos that I have seen about electronics in a while
Thanks
I use this trick for all my portable projects. Excellent protection from the effects of alcohol.
@Afrotechmods that is exactly what I saw in the sim, and would expect. Thanks for the videos. Your time and effort making these videos are greatly appreciated. Thank you.
@colt4547 You absolutely can. But the downside is that you introduce a few milliohms of resistance on your ground rail, which may or may not be a problem depending on what you are doing.
Very nice explanation. I teach electronics at a local community college, and I will definitely suggest your TH-cam channel to my students.
Great video! I like how you were descriptive as possible, while creating an interesting video.
ONE of the BEST videos .Crisp and Clean.. Well done
I love coming to your channel and videos to "wrap up" my understanding of various topics. I'm newbie and just getting back into using p-channel mosfets. I had an ok understanding of how to read the p-channel data sheet to choose the correct transistor for my app however after listening to this it makes complete sense - I wish all my teachers were like you "back in the day" (or at least I wish they had youtube when I was in college lol) - thank you!
@LiKBeAsT I've thought about doing such a video. There are just too many things to make videos on... Anyways when we are not talking about ground meaning the earth's ground, ground can be anywhere you want in the circuit. It is a reference point. You can choose the ground node to be anywhere you want and do your design & analysis based around that. However, using certain nodes makes things easier than others. Most of the time it's easiest if GND = battery's -ve terminal.
Finally the physical explanation I was looking for. Many Thanks🙏
Excellent solution, I was wondering about the wasted power of just using a diode. Thanks for a great answer at the right time
You do such a great job with the presentation: comprehensive and thorough.
Excellent in all aspects. You have more than earned my admiration, and subscription.
@LiKBeAsT "So when it's not ... choose which ever one we want (without being too supid:P) ?" Yes.
The mistake you are making with the battery is that you are viewing the + terminal as an absolute value of +12V. Voltage is always relative, between two points. The batt's + terminals is 12 volts higher than the batt's -ve terminal. So if we declare GND to be at the batt's + terminal, the -ve terminal has to be at 12 volts less than that.
I miss this guy
dazzling presentation. you're the electronics prof i never had. long line afrotechmods
Thanks for covering the P-MOSFET VGS part as well. I corrected my design at the last moment. Thanks again.
Afrotechmods, you are truly a master!
THANK YOU. CLEAR. EXACTLY WHAT WE WERE TALKING ABOUT AT BREAKFAST; AND YOU'VE ALREADY DONE IT !!!
I WAS USING THIS IN SOLAR PANEL DESIGN ELIMINATING DIODE LOSS.
LOOKING AT N CHANNEL FOR LOWER RDSS. NICE TUTORIAL, THANKS AGAIN.
love ur sense of humor. great vid too! I love to blow things up. ran 5v through a 3v led, lens cap got hot, exploded sending the cap through the ceiling tile AUSOME!!!!!!
In p-channel.. load is always connected to source.. when gate is pulled down to ground, the current flows from source and passes through the drain into the load. Mosfet is bi directional. Your video is trying to tell the opposite way if I am not wrong. Your explanation is pretty good. @ 2:39 if the mosfet is ON , then body diode turns OFF. @ 2:39 both are conducting which is a big flaw.. Body diode is ON when the FET is OFF... I am just trying to explain it. Your videos are awesome...
Good demonstration. Nice clear voice that is easy to understand. Looking forward to more of your videos. You have a new subscriber.
Awesome tutorial, very clear and definitely not a waste of time, like many others out there! Thanks a million!
very good video. Everything explained was to the point. You must be the expert in Electronics. Thanks
Hello @Afrotechmods! At minute 3:00 in the video you subtracted 11 Volts off of 0 Volts. Could you please explain why you did it in this order and not the other way around (11V - 0V = 11V)?
That's just how you calculate the voltage between two points. The formula is at the bottom of the screen. More generally, V12 = V1 - V2. And this is of course always referenced to whatever the ground/common node in the circuit is.
Awesome explanation, we do this at work but many an engineer just take it as tribal knowledge, it is refreshing to have the principal explained as the teacher would explain it to the pupil.
The greatest tutorial I have ever seen!
There is also a way to connect a diode in parallel with the load, but this will damage the power supply.
The method shown is a well-thought-out practical circuit.
super hard to find information oh HOW to use a diode but this was very clear and helpful and I finally understand what it does
Man, I'm just seeing this wondering how to do this earlier today, and I already sent out my PCB design for manufacturing! Such timing.
Great video, came up on my page 9 years later!
Excellent video & description of MOSFET usage especially the Rds value
Very clever design and an excellent lecture on how it all works!
Brilliant videos.. practical, concise and clear... and love the bits of humour as well..
Clear, concise and very thorough, what a great
resource - no wonder you Teach! muchas gras.
roBot
Thank you very much, someone FINALLY!!! did a video on this. I've been looking for this particular answer for a week or two by now. First one was the SINE WAVE-MADE PURE was my first & of coarse the second one fell right into order with what I needed. I subscribed so hopefully I'll get any new ones on these subjects. Thanks again, Tom.
Keep on Afrotchmods you'r doing great.
To complete the analysis, you can show that the power lost by the 100Kῼ and diode is far less than the 1.7W across a forward-biased diode; power dissipated by 10V across a 100Kῼ = 0.4 mW? That's around a 3 decade improvement! Excellent by any standard.But at that voltage, the 100Kῼ only allows 200uAmps through the Zener. That might not constitute a high enough keep-alive current for the diode to work. At any rate, that was nicely done. Thanks for the crystal clear sequence of analysis.
Excellent, easy to understand, very well designed presentation!
This limits Zener current. Máximun R value is calculated using Iz (reverse current when Vz is reached, typically a very small value). In this circuit: R = (30 - 10) / Iz
As R= 100k, Iz must be 0.2mA
In my opinion, you can use this 0.2mA value without fear of making a mistake, but you can take 1mA just to be sure
Your videos are awesome. I was watching a few of them trying to connect the dots for a simple reverse voltage protection circuit that doesn't have a big forward drop (I'm splitting the output from a computer power supply to try and power a few ultra-low-power boards from one). Then I saw this, which makes those leaps for me. AWESOME. Also, if you think there's any huge red flags I should watch out for in my project, please say something. :) Otherwise, keep making videos for the rest of time.
Woooaahh!! If only this was the level of quality on solar forums!
Dude, you re great. Am new to your channel but never too late to be a subscriber. Great contents out there. Thumbs up to
Great video! I literally just ordered some assembled PCBs with diode protection just this morning before watching this. should have implemented the mosfets instead doh!
thanks for the great explanation
@DracoXul You could do that, but then you get double the voltage drop and therefore twice the heat in all situations. Personally I think it's better to have something that just doesn't work when you plug things in backwards, then you can just flip the battery around. 99% of the time you are going to plug it in the right way around anyway.
Excellent. Just what I need. I'd heard of doing this but didn't know which FET to use or how to connect it. I previously used a reverse connected diode, by accident I connected the battery in reverse one day, sure it passed a lot of current, blew the fuse and saved my circuit but it blew the end off the diode. Another diode needed.
This sounds ideal.
And I was sober at the time. It was moment of madness.
being an electronics newbee, i really enjoyed that, thanks.
You are a really good instructor!
You can do the same thing by using N-channel mosfet, and it will be more efficient. But you have to connect the mosfet to the low side. If you don't have problem with placing some circuit element between the circuit ground and outside ground, I suggest using N-channel mosfet.
AhmedHan,
How is N channel efficient ?? care to elaborate ?
@@robotboy3525 N-channel uses electrons as charge carrier, while P-channel uses holes.
If you go to any semiconductor part seller (e.g.; Digikey, Farnell, Mouser, etc) and enter the same mosfet parameters (Rdson, Vdsmax, package type, Ciss, ect) as filter, you will see that a similar N-channel mosfet is very cheaper than the equivalent P-channel one.
Holes vs Carriers ??? So by using electrons as carriers how does that make it more efficient?? Also when you say cheaper, are you referring to the pricing ??
Based what I learned from an electrical engineer, n-channel is much faster since it paves the path to ground but it is the most dangerous.
Pretty much all reverse voltage polarity integrated circuits on the market uses p-channel. Thus I think this would be the case because safety comes first.