Kirchhoff's Law VS The VRM : Do DC-DC Buck Converters Break The Laws Of Physics? KVL KCL

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  • Опубликовано: 29 окт 2024

Комментарии • 54

  • @darrenbird2526
    @darrenbird2526 7 месяцев назад +7

    We are getting very spoilt lately! Lots of "Learn Electronics Repair" whilst I'm doing my electronics certificate! Love them! Thank you once more!

    • @tiggydorset9041
      @tiggydorset9041 7 месяцев назад +2

      I've just started an Electronics Diploma myself. This is all great stuff!

    • @MrSummitville
      @MrSummitville 7 месяцев назад

      @darrenbird - Except, 10 amps (steady) does *not* flow in the Upper MOSFET, when ON. Pure nonsense ...

    • @LearnElectronicsRepair
      @LearnElectronicsRepair  6 месяцев назад +2

      @@MrSummitville When did I ever say that 10A steady flows in the upper MOSFET? Timestamp in this video please.

    • @MrSummitville
      @MrSummitville 6 месяцев назад

      @@LearnElectronicsRepair if you are applying Kirchhof's Current Law then explain how you measured 10 amps, if it was not steady? The current through the coil is approx 120 amps, not 10 amps. You need to learn how Buck Converters work *before* making a video.

    • @LearnElectronicsRepair
      @LearnElectronicsRepair  6 месяцев назад +8

      @@MrSummitville I didn't measure it as this was a theoretical video not a practical one, but reality and previous experience tells me this is the case. Let's go through it again.
      The DC-DC converter is supplying a load, let's say a GPU as I mentioned that in the video.
      The GPU requires a supply of 1 Volt and it draws 120A as it dissipates 120W.
      The ATX PSU (as this is a GPU so that's what the PSU would be) supplies power to the DC-DC converter. If the load power (Wattage) is 120W then the supplied power must also be *120W (first law thermodynamics, energy can neither be created or destroyed) *ignoring efficiency losses as this was a theoretical discussion. I also know that in reality this would be a multiphase VRM and I did mention that in video but it is not important for this video.
      To supply 120W at 12V the PSU must supply 10A (10Ax12V=120W) Therefore if I put a current meter into the 12V lead to the GPU I will see a supply current of 10A. We also know this is true as the ATX can not supply 12V at 120A anyway.
      Due to the above facts, the node between the junction of the MOSFETs and the inductor APPEARS to have 10A going in to it and 120A going out of it which breaks Kirchhoff's Current Law. Just as an aside I dislike the use of the word 'node'here, it just makes KCL sound more obfuscated, why not call it a junction like everyone else calls the points where two or more components connect?
      This video was intended to explain how in fact KCL and First Law of Thermodaynamics are both being satisfied by demonstrating that this is a phased circuit which exists in two different states alternately, not concurrently. I then go on to show that each state does indeed obey Kirchhoff's Current Law. As I mentioned I'm open to constructive criticism, for example I don't delete comments that disagree with me. I'd be interested to hear your reply on this topic and why the above description is wrong, if it is. 🙂

  • @josuealexandericujac7083
    @josuealexandericujac7083 5 месяцев назад

    Your videos have been a game-changer for me as an engineering student diving into electronics. Initially struggling with a lack of theory from my professor, your content has provided clarity and ignited my interest in the subject. Thank you for your dedication to education and inspiration

  • @curtisroberts9137
    @curtisroberts9137 6 месяцев назад

    Amazing description and analysis. Made something complex quite easily understandable. Thank you for sharing.

  • @justmc62
    @justmc62 6 месяцев назад

    Thank you Richard for preparing these theory/instructional videos . I appreciate your getting down to the nitty gritty explanations . As a lifelong electrician and electronics hobbiest I find it tremendously helpful .

  • @HsMals3n
    @HsMals3n 6 месяцев назад

    Thanks man! Really boiled down, simplified and applicable!

  • @C5films
    @C5films 6 месяцев назад

    Richard, you're an absolute gem! Making my learning journey all the more enjoyable. If I make it your way I'll buy you an ice cream!

  • @johnfitzpatrick2469
    @johnfitzpatrick2469 7 месяцев назад +5

    Thank you for explaining Kerchoffs Law, it's origin and the Law : the sun of all the circuits will equal the supply voltage.
    Also the demo schematic of two phases within a circuit.
    🌏🇦🇺

    • @MrSummitville
      @MrSummitville 7 месяцев назад +1

      No, 10 amps (steady) does *not* flow in the Upper MOSFET, when ON. Pure nonsense.

    • @LearnElectronicsRepair
      @LearnElectronicsRepair  6 месяцев назад +6

      @@MrSummitville I don't recall every using the phrase '10A steady' could you please give the timestamp when I actually said that in the video before accusing me of saying it? I believe you are putting words in my mouth that didn't actually come out of it! 😶 I did say that this circuit operated at high frequency, into the hundreds of KHz and that the current flowing into the node from the PSU could for example be 10A and the current flowing out into the load could be 120A, which appears to break Kirchhoff's current law, and I stand by those statements. And by my explanation.

  • @miosz8531
    @miosz8531 5 месяцев назад

    Amazing, thanks for explain :)

  • @LocTranTan-r1w
    @LocTranTan-r1w 7 месяцев назад +2

    thank you very much

  • @Lightrunner.
    @Lightrunner. 7 месяцев назад

    Hi Richard 🤗🤗 here the answer.
    I must use Google translator.. sorry my english skills they aren't high enough .
    First law of thermodynamics The first law of thermodynamics describes the principle of conservation of energy and states that the quantity of energy is conserved in every process in a closed system. It is calculated using the following formula: ∆U = ∆Q+∆W The following applies: The change in the internal energy U of a closed system is equal to the sum of the change in heat Q and the change in work W.
    Conservation of energy Energy can neither be created nor destroyed. It can only be transformed from one form to another. Although the amount of energy in a closed system remains constant, the usable portion of the energy varies depending on the conversion. Since Einstein's theory of relativity, we have known that energy can be converted into matter and vice versa.

  • @GiC7
    @GiC7 7 месяцев назад

    Thanks, Richard, great lesson. So, a mosfet, I have to see as a switch 1 or 0, do they do other things too? Now I understand about the coil, that I'm seeing on all the boards and other devices. Now I'm understanding why capacitors are alway loaded . They are like a power-battery, how do we dischart a capacitor? So when I'm making a diagram for something, I have to start from externe load and work to the internal component, which is driving the external, because the board has a low voltage and the load is working on a higher voltage and Amp? I like the lesson, we are building it from scratches, yes.

  • @jonathanrose456
    @jonathanrose456 7 месяцев назад

    Best one yet 👏👏👏

  • @ElectronicWorkshop
    @ElectronicWorkshop 7 месяцев назад +4

    well explained as usual,

    • @MrSummitville
      @MrSummitville 7 месяцев назад +1

      His explanation of ... 10 Amps flowing in the Upper MOSFET, when ON, is 100% wrong.

  • @naeemhaq3504
    @naeemhaq3504 7 месяцев назад +2

    good effort young boy

    • @MrSummitville
      @MrSummitville 7 месяцев назад

      No, there is not a steady 10 amps flowing when the Upper MOSFET is ON! At best, this video is a very poor effort.

    • @LearnElectronicsRepair
      @LearnElectronicsRepair  6 месяцев назад

      @@MrSummitvilleI tried to explain how we could appear to have different currents flowing into and out of a node, contrary to Kirchhoff's law and without using mathematics which a lot of people self included hate. I'm always up for constructive criticism, so how would you improve the video? And when did I say steady 10 amps flowing through the upper MOSFET? Quite the contrary, I made a point that voltage leads current in an inductor. Are you just imagining things here? Timestamp please to prove your point.

    • @naeemhaq3504
      @naeemhaq3504 6 месяцев назад

      @@MrSummitville no problem keep on trying

  • @MrSummitville
    @MrSummitville 7 месяцев назад +2

    No! In Steady State mode and Continuous Current Mode ( a safe assumption ) ... The current flowing through the inductor is *never* 10 amps. The current in the inductor oscillates up and down (slightly) around 120 amps. When the Upper MOSFET is ON, the Inductor is Charging - the current in the inductor is rising, from slightly below 120 amps, to eventually slightly above 120 amps. Then when the Lower MOSFET is ON, the Inductor is Discharging - the current in the inductor is falling, from slightly above 120 amps, to eventually slightly below 120 amps. Repeat, over and over. Each MOSFET takes it turn, flowing approx 120 amps, when ON. The *TIME* that each MOSFET flows approx 120 amps, is different. Your analysis of how a Buck Inverter works is flawed.

    • @PetervanVelzen-l1f
      @PetervanVelzen-l1f 7 месяцев назад +1

      You are completely right …..

    • @LearnElectronicsRepair
      @LearnElectronicsRepair  6 месяцев назад +1

      To All: As this comment was made several times, I've continued the discussion in the pinned comment so it is easier for everyone to keep track of it and join in if you like

  • @skysurfhf
    @skysurfhf 6 месяцев назад

    But when the inductor collapse, don't form a negative voltage, and a anti-clock Path? From inductor, MOSFETs low side, load ? I don't understand that? Thanks for sharing your knowledge...

  • @tonysheerness2427
    @tonysheerness2427 7 месяцев назад +2

    Brilliant.

    • @MrSummitville
      @MrSummitville 7 месяцев назад

      No, not Brilliant. The Upper MOSFET does not flow steady 10 amps when ON. Pure nonsense.

    • @LearnElectronicsRepair
      @LearnElectronicsRepair  6 месяцев назад +1

      @@MrSummitville As many times as you post this statement I can reply. Prove your point with a timestamp please, when did I say Upper MOSFET flows steady 10 Amps?

    • @MrSummitville
      @MrSummitville 6 месяцев назад

      @@LearnElectronicsRepair You clearly have no clue how a Buck Converter works. There is no time when 10 amps is flowing through the inductor. You drew the red arrow and said 10 amps flows like this. No, 10 amps does not flow through the inductor.

    • @LearnElectronicsRepair
      @LearnElectronicsRepair  6 месяцев назад +1

      @@MrSummitville To All : I've continued this discussion in the pinned comment, to keep it all in one place so everyone can follow along and join in 😉

  • @lesioidea
    @lesioidea 6 месяцев назад

    Hi richard
    Thanks for all the videos you making i repair one of my GPU but one is beyond my skills is there any option i can send it for repair ?

  • @danielzeballos7509
    @danielzeballos7509 2 месяца назад

    El Mosfet es un componente no lineal, no aplica la Ley de kirchhoff. El analisis o calculo de circuitos no lineales es mas complejo. Se puede linealizar o calcular por etapas o fases como se hace con el diodo o transistor.

  • @rostamostmann9657
    @rostamostmann9657 7 месяцев назад

    I'm glad I watched this and didn't skip it. Great video.

    • @MrSummitville
      @MrSummitville 7 месяцев назад +1

      His explanation of how a Buck Inverter actually works is 100% wrong.

    • @LearnElectronicsRepair
      @LearnElectronicsRepair  6 месяцев назад

      @@MrSummitvilleTo All : I've continued this discussion in the pinned comment. Please keep it there so everyone can follow along more easily.

  • @andymouse
    @andymouse 7 месяцев назад

    I think you should of made it clear ( clearer ) that this is your interpretation of the 'Law' because Kirchhoff said 'equal zero' because he was taking into account of power and time, a voltage is dropped across a resistor and when all the drops ( they are negative) are added together the result is zero. I say this because I think second or third (Ish) comment down said " Thank you for explaining Kirchhoff's Law, it's origin and the Law : the sum of all the circuits will equal the supply voltage " That is not what Kirchhoff's law says. I think an explanation as to why the law is worded as it is would be helpful for those who want to pursue the algebra. Just a little whinge, as there are other channels that enter into theory whilst reading it all from a book and getting it all wrong and all the time giving the impression they know what they are talking about !! I'm sure you have come across such channels in you illustrious RUclips career

    • @LearnElectronicsRepair
      @LearnElectronicsRepair  6 месяцев назад +2

      I do believe I showed the actual wording of Kirchhoff's law in the video and then said that 'but this is the way I like to think of it' (which I guess means how I like to interpret it...)
      Taking the power source as a positive voltage, then adding the sum of all the load voltages as negative, would of course give a result of zero. Is that any different from me saying that adding up all the load voltages would give a result equal to the power source voltage?
      I hoped to explain this in a way that did not involve maths but would still explain these important laws to non mathematical viewers. It seems in this case I upset a few people by trying to do that...

    • @andymouse
      @andymouse 6 месяцев назад +1

      Nah not upset ! still love ya just curious keep 'em coming I'm sure it's realy hard making these vids anyway without the maths, thats why I watch and not make !!:)@@LearnElectronicsRepair

    • @LearnElectronicsRepair
      @LearnElectronicsRepair  6 месяцев назад +2

      @@andymouse Actually you were not the one I seem to have upset 😉

    • @andymouse
      @andymouse 6 месяцев назад +1

      Yes, I see that now ! :)@@LearnElectronicsRepair

  • @clintonscholtz8182
    @clintonscholtz8182 6 месяцев назад

    The Civil Rule just made me feel like trouble shooting all failed devices i have trouhgn away.
    .

  • @Dutch_off_grid_homesteading
    @Dutch_off_grid_homesteading 6 месяцев назад

    Heya, ?!?!??!?? oke KVL and KCL now I see it I remember I had it at middel high school and it's logical for me. I see and untherstand the 2 phases intergrated into 1 circuit ( unlike a transformor with 2 circuits) what I don't get is how the load can handle 1 moment 10A and the next moment 120A and yes I'm a student well try to be and I read al the comment's( difficult because I don't know al these thormodynamics law's and maxwells equation ) and I untherstand P1=P2 so I1xV1=I2xV2 10Ax12V=120Ax1V and still I don't get it, mind boggling. please explaine more thanks

  • @Monaco-BuilditFixitDriveitEver
    @Monaco-BuilditFixitDriveitEver 6 месяцев назад

    That gibberish is a bit deadly!

  • @PetervanVelzen-l1f
    @PetervanVelzen-l1f 7 месяцев назад

    I am sorry Richard, but your explanations of how a synchronous and/or a buck converter work are wrong. If you were right, the top mosfet would be ON much more time then the bottom mosfet - which is not the case. Your explanation simply ignores the dynamics of these circuits - sorry to say so.

    • @LearnElectronicsRepair
      @LearnElectronicsRepair  6 месяцев назад +1

      Did I ever say that the top mosfet it one for a much longer time than the bottom one? I think I said that the top mosfet effectively stores energy in the inductor, and the bottom mosfet (or diode in case of a buck converter) releases that energy via the load. At least that is what I meant to say.

  • @wolfgangrichter6088
    @wolfgangrichter6088 6 месяцев назад +1

    Richard, please please show us videos without end in which you tell us how to repair devices.
    Your excurses into theoretical physics will rather disturb the minds of your viewers.
    Im already curious to hear you explain how Mr. Kirchhoff manages to get current from one coil of a transformer
    to the other even if there is near infinite resistance between them always.
    Your phase-theory will not help you in that case. Sooner or later you have to accept that there are additional
    effects in electricity like the law of induction which was, by the way, discovered by Mr. Faraday
    who maybe knew even less mathematics than you do. Despite this he was one of the most important physicists
    of his time. Kirchhoff was one of the founders of mathematical physics but he worked at a time when
    the understanding of electricity and magnetism was a big mess still. Today he would be a fervent supporter
    of Mr. Maxwells equations form which the Kirchhoff rules follow under certain circumstances.

    • @LearnElectronicsRepair
      @LearnElectronicsRepair  6 месяцев назад +3

      Quite simple that one. The primary circuit and secondary circuit in a transformer have galvanic isolation. Therefore KIrchhoff's laws apply to both primary and secondary circuits separately. What we can also say is true is that the conservation of energy still applies (first law of thermodynamics) so the energy in the primary and secondary circuit are the same: V x I in the primary = V x I in the secondary (minus some efficiency losses dissipated as heat to satisfy first law thermodynamics). I was honestly of the opinion that understanding basic laws like Ohms and Kirchhoff's are essential to being able to repair devices, hence these sort of videos from time to time. I'll let others comment on whether they agree with that or not, but ultimately I use the views/hours analytics which tell me what sort of videos people here like to watch and what they don't. 😉

    • @wolfgangrichter6088
      @wolfgangrichter6088 6 месяцев назад

      @@LearnElectronicsRepair : The first law will even allow thermal energy to be sucked up by the secondary and transported to the
      primary as free electric energy. This does not happen very often. My answer is 12MHPE.

    • @russelpinkard9489
      @russelpinkard9489 6 месяцев назад

      Thanks for this. I think this level of simplification is just right for people who just want to make stuff work! Keep up the good work.