Designing Power MOSFET Circuits - Circuit Tips and Tricks
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- Опубліковано 28 тра 2024
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Designing Power MOSFET Circuits - Circuit Tips and Tricks
MOSFET circuit design and selection is a commonly requested topic for me to cover. There are a lot of uses for MOSFETs, as a result, they have become more commonplace than standard BJT or NPN transistors, especially in high-power applications. I will cover information and equations needed to design useful circuits without getting "down in the weeds" with complicated derivations
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Problem! It's great that you're making videos like this, but I think the power calculation is a bit off. if you're going to deliberately slow the on-off and off-on transitions, then those transition times are durations when the MOSFET will have to conduct significant current while exhibiting significant resistance. This can easily dominate the heat output.
Yes, you're right. I had to limit what went in the video, and was focusing mainly on high-power low switching speeds drives. But yes, I wish I would have at least mentioned the losses during switching.
@@MicroTypeEngineering Thanks for replying. I'll just add that I think what happens during turn-on/turn-off is especially crucial to mention, because an unaware designer could be lulled into over-optimism by the astoundingly low on resistance that some of these devices have. That low resistance does indeed mean that your sample device can carry very high current, especially given suitable heatsink. But factor in frequent switching, and the numbers blow up, perhaps surprisingly for some.
I'm glad you two brought this up. Thank you for the video, MTE!
So should we reduce the gate resistance to speed up the on-off transitions?
@@dwalden74 Right, you would reduce the gate resistance according to the calculations that MTE did in the last 5 minutes of the video. That's assuming the gate driver chip can handle the current pulse and isn't the limiting factor. But first, you would first want to assess how much heat is dissipated during those transitions to see how fast you need the transitions to be. If you are switching infrequently, then slow transitions are not much of a concern. But if you're switching frequently, then they can easily dominate the heat output. To assess the heat output per transition, conceptually you would need the gate waveform (VGS vs t), then the corresponding RDS (drain-source resistance) vs VGS, so you arrive at an RDS vs t. That's pretty tedious, so instead model it in Spice (for example). The Spice sim can directly plot the power dissipated per transition (just VDS x IDS). And run a range of parameter values, as VGS vs RDS is not a tightly controlled parameter.
Just the first 5 minutes, and I can totally say THIS is the way to explain things. Clear, simple, direct, practical examples. I've seen tons of videos about the same topic, and none of them were useful at all.
Man, you deserve credit. Thank you for the vid.
This is incredible, thanks so much! I especially love how you explain WHY you do certain things. A lot of videos say "oh just do this, put this resistor here" then they move on. But you explain WHY certain things go there. I love it cause it helps me learn!
Glad it was helpful!
Agreed - the "why" is so often missing. This has been a marvellous video.
I've never seen a video that holds all the information needed in less than half an hour! Right into the point like an arrow! Well done.
Thanks, glad you enjoyed!
Perfectly practical introduction into using a mosfet with MCUs.
Glad you liked it!
"Theres not a whole lot of in between" - I have observed this on many topics. It is the curse of the internet. So much information, so little relevant information.
Wow.. you make things so much easier to understand. You dont assume we know anything at all and its great. Everything you say if it isnt obvious, you breifly explain what you meant in laymans terms. Thank you!
A concise, to the point explanation in a language the 'mortal' being can understand without the 'gobbledygook' and 'dreaded' calculus. Great stuff, keep it up!
I have a degree in EE, but I never had such a clear explanation from any of my professors back in school. Well done!
@@jamescollier3 The circuit in this video is using the mosfet at it's most simplest function, as switch. So normally you would wire your "load" (led, motor, etc) in series with the switch (mosfet). Mosfets are popular as switches since they dissipate very little power compared to transistor switches.
The video you linked to is using the mosfet as an (analogue) amplifier. Without going into the many different amplifier configurations (some which have the speaker in series with the mosfet) the results, conditions, and calculations are different.
I never thought about that gate inrush current before! And here I was with just a 10K pull down for my Arduino.
This has been the most helpful video on MOSFET's I've seen yet. Thank you!
Wow, thanks!
I completely agree. Too many videos rely on music, obnoxious antics, weird visual effects, and the like. A simple factual presentation that covers the crucial aspects with explanations is an increasingly rare thing, and definitely appreciated.
Yeah I agree this was extremely helpful
Thank you for teaching that so well. This is the first bit of info I've come across that actually helps me make an informed decision on which mosfet to get. Thank you for taking the time to make this video.
Now that was an excellent explanation! This is probably one of the clearest and and most thoroughly explained videos about any electronics topics that I have ever seen (and there are quite a few great ones out there). Very well done. Thank you!
Wow, thanks!
WOW. Great job...I learnt without frowning and scrunching up my face. The information just went straight in. I will be watching ALL of your videos. Thank you.
Excellent overview! Thank you for doing this.
Extremely well explained thanks, I still have a long way to go but with tutorials like this half the battle is won
This showed up in recommended channels....how did it know I was working on a large smps for a power amp with blown MOSFETS at that moment. It was a design I did and surely the UA-cam masterminds were trying to tell me something. Very well explained and the production values of your videos are welcome indeed. Thank you. Why only 6k subs? It is 6k +1 now.
Very well explained. You keep it practical. Nice job!
Perhaps the best instructional video for mosfets really clear thank you
Thoroughly enjoyed the crystal clear explanation!
Just saw the comment below on hooking Mosfets up in parallel. Circuit would consist of two,three, or more Mosfets with all Gates joined, all Drains joined, and all Sources joined, apparently for driving really HUGE loads that one Mosfet could not handle. One UA-cam video regarding this is called "Issues on Connecting MOSFETs in Parallel" and addresses some of the problems. It seems that the electric vehicles would have to have multiple banks of Mosfets just to propel the vehicles down the road. Would like to hear your thoughts on this. Thanks again. Great videos.
I don't have any direct experience with FETs in parallel, but typically the reason people shy away from parallel components is that they won't react the same way to the current across them. In some use-cases (fuses), parallel components are OK, since the resistances even out due to heat. But FETs can have their resistances decrease with heat, causing a runaway condition. (I know Vgs decreases with heat, not sure about Rds off the top of my head.)
Clear, concise, pragmatic. Love it mate. I learned a lot thanks to you. :)
I've watched this multiple times, and it has helped so much! They explain components and pcb design tips really well! Thanks so much!
You're very welcome!
I am a huge fan of your design tips
So I needed to refresh myself with a single concise tut on MOSFET's and I found it. Bravo.
i would love to see more educational and practical videos like this from you
I know virtually nothing about any of this, but I watch a lot of tear down channels as I find it very interesting. This video made so many things that those gloss over so clear... such as why there are little circuits with resisters going around the "real" circuits, etc. THANKS!
I really appreciate you taking the time to thoroughly explain Mosfets and how they work in conjuction with the MOSFET Drivers. As a controls engineer I can say this was very well explained and simple to undertsand. Trying to research everything i need so I can design a BLDC controller for a special project I have jumped into to keep my self busy.
Thanks Brother.
Awesome. Wish I had watched this a few years ago, I'm sure it'll be useful to anyone getting into electronics.
Easily, by far, the best guide to real-world use of MOSFETs on UA-cam. Not a home run - a grand slam. It absolutely accomplished the goals stated at the start: genuinely useful, while steering clear of the weeds that others let their viewers/students get lost in. Definitely sets the new high-water mark for the MTE channel. Looking forward to whatever comes next! Thanks much.
Wow, I appreciate the comment :) Yeah, I don't know how I can follow this one up haha!
This is really a handy way to do rough calculations around a power MOSFET. I personally calculate with half of the gate current to get more realistic switching times. Under more critical timing conditions I also consider the internal gate resistance, which is typically in the order of 1 to 10 Ohm. So in some cases you don't need an additional gate resistor or you have to avoid it to fulfill your switching requirements.
The video I’ve been hunting for too long. Thank you, earned a sub!
I've been doin this a while, but sir, this was clearly and concisely explained. Kudos. Subbed.
this is a wonderful explanation! the simple videos you mentioned make it seem so easy to drive but the other videos make it so complicated. you managed to find whats important and relayed that info in a clear and concise way.
I am designing a 9v battery to usb charger and i wanted to add undervolting protection. i found a very low power comparator that has an internal reference that makes it easy. the problem is my buck converter doesn’t have an enable pin. so i have to use something to turn the circuit on and off. i didn’t want to waste power driving a bjt but mosfets seem so complicated. now i understand what to do.
Nice content, thank you! Love the format, simple and calm explanation - that really changes from those crazy super-fast videos out there on UA-cam ;)
Cheers
Simon
Great explanation on driving MOSFETs. Thanks !
Great video! Your explanation was so clear. Nice work!
Instant subscribe. Huge help, thank you!
you are the only one that
had actual values for the resistors big help thank you
Thanks! Just the right amount of detail.
Excellent. You commented on increasing the gate resistor. The thing to watch is that by doing this, you increase the charge time and the amount of time the divine is in linear mode. During this time it is dissipating much more power. If the gate resistor is too high, it will increase the delta T.
This is an absolutely superb presentation. This mechanical engineer is now in with a fighting chance of building a simple dc switch which demands effectively zero gate current once energised. Thank you for improving my education with no pain.
Hats off for well structured and crystal clear explanation.
I love the way you speak and explain things. Thank you
Super happy I found this channel! Will binge every vid soon I think
Welcome aboard! Enjoy :)
This video was amazing! Just what i was looking for
very well explained. thank you!
Most in-depth mosfet circuit explanation on UA-cam . Great job. Thanks
You are welcome!
Very beautiful explanation sustained by a clear and slow speed language! Thank you!
Glad you liked it
Great explanation. Thank you for your time.
Very useful video on MOSFET. Thank you for covering the datasheet parameters and their meaning. Thoroughly enjoyed it. Thank you.
Glad it was helpful!
This is literally what I needed. Thank you!
This man is gold, great work.
This was awesome. Thank you for creating this video.
Great video, thorough and clear! Thanks!!
Clear and refreshing pertinent rational thinking process
Excellent pragmatic presentation. Especially important discussion of gate resistors seldom addressed by many videos.
Great video with excellent explanation. Learnt more from this video than the 20 previous ones combined, subscribed!
Awesome, thank you!
Wow - this is fantastic. So well presented and really useful even for those of us who have been using mosfets for years. New sub for sure :)
Super well explained. Thanks.
Thank you for this tutorial on Mosfets. Posting a further video on IGBTs would be helpful especially because according to my experience IGBTs are more difficult to work with.
This was really helpful, thank you very much!
Thanks for this, it's exactly the level of detail I needed, and from your explanation I can appreciate when and why there are cases where far more detailed selection/calculations would be required. i suspect that for my purposes I'll probably never need more than these basic selection considerations and quick safe limit proximity checks.
Great explanation specially the parts where you refer to the tech data sheets.
Im so thankfull to have found your channel
Thanks for this Tutorial I am grateful for taking your precious time to make this video.
Thanks for the explanation, Now I understand working principal, the design parameters and calculations.
Thanks a lot friend keep up we are with you forever
Your contribution to this field is really unmatched.
I appreciate the words 😊
This video is enough for every MOSFET designer. I appreciate for your efforts. Please, make a video on intricate-accurate MOSFET calculations.
You're such a good teacher.
Excellent explanation and especially you give the reason for using the resistors in gate of mos transistors. Thanks for great and concise explanation.
Nice bit of theory
Liked and subbed ! 👌
Great explanation !! Thanks a lot.
I am glad I watch this video, it's amazing. For a complete explanation about the power losses, it would be better to include the switching losses. Thank you very much for such outstanding explanations.
Wow excellent explanation! Great job!
I learned so much about the mosfet. Thanks a lot for this video. Gtz from Amsterdam, The Netherlands.
Amazing how many EE's don't know how to decode any component's specs. I worked with a lot of just-out-of-college EE's that would read a component's spec and think they could drive parts beyond their real specs using one or two maximum specs as their only guide while forgetting that everything has to be observed. Just because a part can handle 10 amps and 100 watts, doesn't mean you can drive it to that 10 amps at any voltage. And watching them burn up circuits (and their bench tops) was actually funny... Thumbs Up!
Excellent video mate, keep them comming, very well explained. Subscribed!
Thanks for the sub!
This is the last MOSFET video I'll ever search for. I just wish I'd have found it 6 months ago. I've been spinning my wheels. You're smart engineer and have a gift for demystifying the black magic that all too often bars people entry from realizing their applications.
No BS, no stretching, no clickbait titles, no grandstanding or egocentric self promotion.
You got yourself another subscriber.
Woah, thanks for the kind words! Though, I am working on a part 2 of sorts, so you might need to add another MOSFET video to your list! ;)
Finally and finally i got what I searched for a very Long time
wonderfully explained. you should have more subs
Thank you very much. very clear and instructive video!
Bravo monsieur. Keep the good work going. Your prononciation is clear and sufficiently slow so people like me (?) can understand and follow you. I taught at the university level in Canada and I would of liked to have your ease and pedagogic talent of communication during those years.
Amazing! Many thanks.
As always; excellent.
Awesome! I feel like I actually understand basic MOSFETs now!
Me Too!!
Short and sweet explanation, but me (as someone without any experience with MOSFET) has two small remarks ?
At 02:50 :
"... the gate to source voltage, once you get below 2.1 Volt, the resistance from the drain to source decreases exponential."
I think should be:
"... the gate to source voltage, once you get above 2.1 Volt, the resistance from the drain to source decreases exponential."
And this:
" 'Silent' PWMspeed control at an ultrasonic frequency of 20 kHz".
Ultrasonics may start theoretically at 20 kHz, but humans and dogs and other creatures are surely able to hear these frequencies, although it is not part of the bandwidth of our ears. But when the power is high enough we are bothered by it, sometimes without us able to pinpoint the source. So making these designs at least at 30 or 40 kHz is (in my eyes) a must.
Very good instructive video. Information I've been searching for in trying to improve my circuits. Thanks much for making this.
Great to hear!
Thank you so much for such a great explanation, I never had this clear idea before. really useful. 💯
Very well explained. Ist time getting to know what a datasheet mean..
One other consideration with regard to the gate resistor is the situation where the MOSFET fails, typically shorted. In that scenario you have a pretty good chance of applying Vdd to the microcontroller pin that's driving the circuit, with usually unpleasant results.
I am glad to meet you. Seriously. Excellent work. Very useful to me. Thank you very much.
Thanks for the kind words!
I m working as electronic engineer . This video was very informative .Thanks .Expects more videos
Congratulations from Brazil..
This is perfect thank you so much!!!
You're welcome! Glad you enjoyed it
Awesome!!! great explanation, please make a vide for advanced calculations also.
Greetings from the UK.
This was a most interesting and informative video thank you.
I will now be subscribing to your channel
Awesome, thank you!
You did exactly what you said, this is super helpful. Thank you.
You're so welcome!
Excellent information and presentation. Thank you.
Glad you enjoyed it!