FLYBACK DC - DC Converter Theory And Example

[@ELECTRONOOBS]

Sign up at ELECTRONOOBS.io: electronoobs.io/ Follow me on FACEBOOK for more: facebook.com/Electronoobs help me on Patreon: www.patreon.com/ELECTRONOOBS

[@avishekyadav]

Sir please help how I can write my usb serial number

[@franciscojavierramirezaren4722]

Electronoobs Excelente gracias!! Ojalá pudieras construir una fuente HV rf (1MHz - 10MHz) para generar plasma frio!😃

[@mematyi]

Great video! It would be great to have more power supply videos like this, with a bit more depth and calculations, not just this introduction. A Comprehensive, but still understandable SMPS topologies/workings tutorial would be one of a kind on youtube

[@ملكةزماني-ذ4ر]

In solving the DC-DC converter problems how can we determine the mode of operation (continuous, discontinuous, or boundary) ?

[@guillermosantin1053]

Hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhaha

[@NiHaoMike64]

It's worth mentioning that the flyback converter is likely the first switching converter ever built. It was used in gasoline engine ignition systems, first with mechanical switches activated by the camshaft or crankshaft, later replaced with electronics. (Many but not all modern engine ignition systems work that way - some are based on forward converters.) The name comes from mechanics who get zapped by the high voltage and jumped backwards from the jolt. :)

[@ardhi1269]

"FlyBack"

[@BYENZER]

OH! I was wondering why "flyback" wasn't referring to a "flyback diode" or flyback resistor, both used to draining off excess energy out of capacitors and relays after shutdown.

[@NiHaoMike64]

@@BYENZER How many of us played with relays and batteries when we were little kids? The relay coil giving a sting that feels like a static shock probably got us quite a surprise the first time around.

[@BYENZER]

@@NiHaoMike64 The answer to your question is: Most kids never do. But, of those few who did, sadly, (or gladly, depending on your point of view), most of them are now all Darwin Award winners and helped to THIN THE HERD!

[@shafiqrezal2855]

Thanks, i really wondering where the flyback term from 🤣

[@williamthesloth]

Im a simple man. I see new video from Electro, i click like. Keep them coming

[@AirmanCS]

Great video, now as a noob hobbyist of electronics I finally understand how my power supplies works and I can proceed to never ever do any project involving more than 12v because 120v (or 250v) from the outlet are scary as hell lol. But in all seriousness I was this week on my journey on learning transformers how to discharge (or what not to touch) capacitors and this was really helpful. Don't mess with electricity people stay safe.

[@sengtheara6503]

thank you for all the video that you have mad. I find your video is easy to understand and explain more clearer than the other

[@donaldfilbert4832]

Great coverage of the topic. I love the way you build concepts and integrate them on the topic - and especially your great schematics; images; and demos !!! Thanks a ton !! ;)

[@MercyKnow]

تم الإشتراك في قناتك الرائعة وتم تفعيل الجرس وأجمل لايك للفيديو انا من الأردن من أصول فلسطيني

[@rikvermeer1325]

I would like to nominate you for global educator. :) You are able to give such valuable information packed in a way that is understandable. You cover topics in 10 minutes that would require multiple years of listening to a "bad" teacher. Please keep on sharing your knowledge with the world to make it just a fairer place with equal opportunity for everyone.

[@Den_Electro]

Hi, friend. kzbin.info/www/bejne/aaPLiqZsi5Wnd7c

[@sugameltpastriescoffee7186]

The best video on flyback DC DC converters

[@NemoInYoutube]

My next experiment is making a flyback converter. This video is cool! And our lab used TL494 and UC3843 instead Arduino. This video is more interesting than our ppt.

[@hemantbabel4279]

I think you are reading my mind. Its 4 times in a row you uploaded the video that i am researching on. This helps me summarising all the points.😁

[@sadunnakipoglu9471]

أشكرك وأقدر مجهودك ، تحياتي لك من تركيا .

[@Debraj1978]

Flyback transformer also has an air back in its core, whcih is not in usual transformer. That air gap store the energy. Most flyback converter has a small plastic sheet between its 2 pieces of cores, which serves as the tiny air gap.

[@TheSoapyJew]

Incredible detail. I actually understood most of this. Well done and thank you!

[@laharl2k]

Good video. One thing you should take a look at is adding code to the arduino to not only change the PWM duty cycle but also the frecuency, and divide the function into steady and non steady states, so when you are under low loads you can do faster pulses in short burts to get a better regulation with small loads and when you reach steady state (constant pwm) you can lower the frecuency to increase the efficiency (all according to your mosfet and transformer. You can play with the duty cycle, and frecuency to trade off regulation or efficiency. If you just cared about efficiency, you could just ser the frecuency, and duty cycle to the highests efficiency point, and then just turn the pwm on and off depending on whether you are above or below target voltage. And of course your ripple will be huge without an equalized load but for stuff like motors or resistors it shouldnt make a difference because it would be the same rms power, capasitive loads could have problems with the voltage peaks though.

[@ryccoh]

Why do capacitive loads have a problem with voltage peaks?

[@laharl2k]

@@ryccoh Because capasitive loads will suck more power and store it instead of actually generating work with it. Its like having a led with a capasitor at the front. If you give a PWM signal to it, the capasitor will charge to full voltage and then continue powering your led even after you turn the power off (or are in the off half cycle) The capasitor, or better said, capasitive loads will smooth your PWM signal and try keeping it constant, which is the opposite of what you want. In practice you can use PWM with capasitive loads but depending on how capasitive it is and the type of capasitor it has you can either fry your mosfets, output diodes, or even blow the capasitor because of the excesive ripple (the pwm signal itself) or if nothing of that fails you will most likely have a very exponential response, meaning that a 0% you will have 0% power, at 5% you will have 3% power, at 10% youll have 25% power and say at 20% pwm duty cycle you will have most likely 90% or almost full power. Motors and inductive loads dont store energy as voltage but as magnetic fields, which then translate to current. So a PWM signal would make the current raise when on, and fall when off making a sort of low pass filter. This in turn translates in that you can control the average current with your pwm signal which is what actually creates the work. The caveat is that you need to use slower frequencies or you will get a very logarithmic response. Thats why you can hear a faint coil whine with square wave VFDs have that soft start and power control. (Its the VFD doing PWM to the motor coil to limit the max current) Interestingly enough, in theory, if you had a constant current power supply and did PWM with that to an inductive load, you would have the same the same problem as having a constant voltage PSU doing PWM with a capasitive load. If you PWM voltage, you can control current, if you PWM current you can control voltage. Resistive loads dont store energy so they are not a problem, meaning 50% duty cycle equals 50% output power.

[@Den_Electro]

Hi, friend. kzbin.info/www/bejne/aaPLiqZsi5Wnd7c

[@stupossibleify]

The best explanation I've seen on this

[@1986ah]

Thanks for making electronics simple

[@AdityaSharma-vi8ky]

Man I love you, this is best ever video on this topic

[@MaxintRD]

Thank you for this very nice video. It's a great explanation of the working principle and I like how you connect theory to practice by showing it operating in a working example.

[@Den_Electro]

Hi, friend. kzbin.info/www/bejne/aaPLiqZsi5Wnd7c

[@PhD_Yamete_Kudesai_Khalala]

Finally something intresting !!!!!! . Please share more of these vidéos ( power electronics ... ) they are easy to make and intresting . Thank you my friend

[@ELECTROBUFF]

Yeeeees. I like switch mode power supplies, nice video man.

[@d23rfd3gfjhjhgfdze]

This channel deserves more subs!

[@nosafetyswitch9378]

Nice tutorial but the example PSu is not really good at all in terms of isolation distance between primary & secondary is 1mm only at the area on the full bridge diodes and (what i assume is) the GND of secondary side. Decent tutorial though.

[@Den_Electro]

Hi, friend. kzbin.info/www/bejne/aaPLiqZsi5Wnd7c

[@sami-sp4so]

Great video . I just want to highlight a point , in you schematic i think you put the diode in the opposite direction because otherwise the capacitor will discharge into the battery which is not good for a boost converter.

[@davebutler3905]

Superb explanation. Thank you!

[@stefano.a]

Awesome explanation

[@ziadbrakat5421]

I love this kind of video

[@sethusubramanian9214]

Nice theory tutorial ....expecting more tutorials like this in future...i would like a vedio about working of radio controllers used for communication.

[@Den_Electro]

Hi, friend. kzbin.info/www/bejne/aaPLiqZsi5Wnd7c

[@hadzrinekosni4530]

One of the best tutorial that i've seen..⭐⭐⭐⭐⭐🤩👍👍👍

[@aravindhuaravind781]

Your videos are very good and useful . I used ur esp server in my project. Thankz

[@marvelous9300]

Great vdo.... With full animation

[@electronic7979]

Helpful information. I like it

[@jimis04]

Very simple explanation of flyback operation but on 7.23min there is something important that is not said and must be mentioned. When switch opens inductor l1 forms an opposite voltage as to the one before switch opening. So the same polarity is formed the same time on l2 dots. Negative on the dot of l1 (positive before switch opens) and positive on the other. Same on l2. If switch was drawned on the negative side of l1 things would be a bit more clear about the polarity formed after switch opening. Also something that is inportant and cant be forgottend due to simplicity. The dots when drawing inductors is not just a mark. Its on the same side of a coupled inductor if the winding was made using the same direction when winding the core. And in the opposite direction if we used opposite directions.clockwise vs anticlockwise

[@jimis04]

Correct! I entered comments to write about the messed up description of dot theory in the video...

[@abhisheksitalagere9344]

good information sir thank you. sir by using this converter i can design step up converter or not? because i want to step up the voltage from 390v to 1000v is this converter is suitable? let me know sir please.

[@TheHarpanOnly]

Thank you for the clear explanation

[@MCsCreations]

Really, really interesting! Thanks a lot, dude!!! 😃

[@user-wy3xe2tt3y]

Excellent video 👍🤓

[@Li0rE]

First of all - amazing video and this has been extremely helpful for me in learning about coupled inductors and also mosfets. In your schematic, it looks like your diode is in the opposite direction of what it is when you demonstrate it on the breadboard. Was this a mistake?

[@ShawClash]

thank you for the tutorial i was trying to make the isolation ground circuit for the sub woofer which was cause of the noise this circuit could be the trick for canceling the noise i hope this will work in many of my projects

[@samwillard5688]

I have been using an old ATX power supply to run a robotic arm. Last night, my output changed from + 12v to a very low voltage AC. I have no idea how or why this happened. I am using a premade chip for the 24 pin connection. Perhaps this is the failure>?

[@acoustic61]

Good explanation. However, I think one of those two transistors is a diode?

[@Scrogan]

Are common-mode suppression chokes not using a lossy magnetic core? I’d be very hesitant to use anything designed for noise suppression as a power inductor/transformer for this reason. Not to mention flyback transformers in particular need to have an air gap for storing energy. Trying to use a conventional transformer (or even a transformer from a forward switching converter) for a flyback converter definitely gives you problems.

[@d614gakadoug9]

Common mode choke cores are not generally lossy, though they may be for some special applications. Normally they are "ordinary" ferrite with permeability in the range of 2 to 4 times that of typical power ferrites (5000 to 10 000 vs about 2800). Without an air gap the core will saturate at pretty low volt-second product across a winding. The winding design is also poor in terms of leakage inductance. I suspect the only reason the FET in the circuit in the video didn't die from having to cope with excessive leakage inductance is that it's drive was poor and switching was slow. I'm rather baffled by the weird ramping waveform in the video - the two distinct ramps, rather than just one. I'm assuming it is the primary current, but it certainly doesn't look like anything I'd expect (and I've designed a lot of switchers).

[@АнтонЛяпощенко-о3о]

Isn't a common-mode choke supposed to be lossy at high frequencies? Or is it fine at such a low power?

[@d614gakadoug9]

Generally that type of CM choke isn't lossy, though some are made to be. They are a poor choice for a flyback converter because they are able to store comparatively little energy and so can saturate easily (i.e. above some point the core ceases to be able to sustain more magnetic flux and the winding starts to look like just a resistance, which can result in instant destruction of the circuit if no protection is used (many controller ICs for switchers monitor the current in the primary and if it exceeds a threshold the chip turns the switch OFF for the duration of the cycle). Inductors for flyback converters normally employ an air gap in the magnetic path. With a ferrite this is done with a discrete gap. With an "E" shaped core a apscer can be used so the gap is in all legs, but the preferred method is to grind the centre leg so all of the gap is there. With "powder" cores, such as powdered iron or molybdenum permalloy powder (good, but really expensive!) the air gap is "distributed" and actually made by the non-magnetic binder material that holds the magnetic particles together. In a gapped core almost 100% of the energy is stored in the air gap.

[@atom2319]

Thank you, very well explained...

[@keithking1985]

That was a very cool video.. Thanks😁

[@matthewmorrison2071]

How is their a voltage gain if the coupled inductor ratio is 1:1 would it just be the same voltage from primary to secondary coils

[@chibuzoeze4225]

Thank you very much sir, Pls can I achieve solar charge controller through this topology? If yes, pls which is the best for pwm

[@amoghjain]

At around 11:12 you mentioned that using flyback will create ripple due to switching and this supply is not much useful. Cant we add caps, and use a LDO to ensure the ripple stays minimum?

[@saulrosal4134]

This is awesome!!! You are great!!

[@elyesmehri3067]

Thank you that's so clear

[@nidhinbenny7975]

Why do we need a BJT as a MOSFET driver? Can't we turn the MOSFET on and off using signals directly from the arduino? Or do MOSFETs require higher turn on voltage than the Arduino can provide?

[@d614gakadoug9]

Many FETs do require a gate-source voltage above 5 volts for good turn-on. You also need a driver that can source and sink substantial current in order to rapidly charge and discharge the gate's capacitance. Even in very old SMPS control IC's the drive current capability was usually at least ±200 mA. His driver arrangement is poor, but it actually probably is advantageous becouse of some other poor choices in the circuit.

[@knownshareit]

In your schematic, Why didn't you switch the mosfet directly from the Arduino? Would anything happen if they were connected without using the bc547 transistor?

[@monodipsarkar9805]

Arduino pin can't supply enough power to do that. That's why it's needed to switch using another power.

[@sharana.p5921]

Thanks for uploading this video. Pls tell me which software are you using for animation. Thank you

[@legominimovieproductions]

So if I need a dc power supply that is insulated from mains I would need a flyback design? (I hate getting 80 to 150vac between DC+ or DC- and earth or L/N

[@hichamtassi1753]

Hello, nice video ! i just got a led driver (s-150-24) but no power at the capacitor for VCC PWM. I checked the voltage coming to it from two 570 K ohm, but end up having 0v. No component seems burnt, any idea where to look at ? thanks

[@SanjaySharma-pw6ww]

Nice video. Pls tell me how to calculate the frequency and inductance of primary of these types of smps.

[@Ahmadnaweed786]

you nailed it man! best

[@1828fernando]

The schematic Is incomplet, you can use an lc filter at the output. This filter Is in your power supply example !!!

[@SanjaySharma-pw6ww]

Pls tell me how the frequency is been calculated in this RCC circuit. Do we have any formula for this. Pls also tell the components in oscillator part of this circuit

[@tahirbintariq8934]

I can say you explained half of the circuit because tha back emf created by transformers should be handle with snubber circuit and this create a lot mathematical confuaion for engineers😊

[@d614gakadoug9]

The "spike" is the result of leakage inductance - magnetic flux that is not well coupled to the output winding. I don't know why it should cause a "a lot of mathematical confusion." It is quite straight forward, though actually quantifying leakage inductance can be a bit of a challenge. If a discrete FET is used it may, if the inductor is well designed, be completely acceptable to allow the FET body diode to avalanche to discharge the leakage inductance, though this has to be evaluated carefully. This approach usually can't be used with integrated switcher ICs (e.g. those from Power Integrations), where the maximum switch voltage rating must be carefully adhered to.

[@azenarnoriv403]

How many volts in the input my frnd? Tnx for the nice explanation my frnd

[@Sam-yz7vm]

very nice very clear 🙏

[@christianstrohmaier3675]

How did you manage the voltage spikes at the drain of the MOSFET?

[@RandyLott]

You can use a snubber circuit.

[@christianstrohmaier3675]

Thanks. I tried using Zener diodes but heat is a problem. What kind of snubber do you suggest?

[@franciscoshi1968]

@@christianstrohmaier3675 fly back converter are one of the most inefficient of the switched mode power supplies. The problem as you found out is the spikes on the primary. There is some stray inductance for each winding which is not coupled to the other winding. When you turn off the switch the energy stored in the stray inductance of the primary can not be transferred to the secondary and has to be absorbed in the primary side. The way the transformer has been wound on the video makes this problem worse but helps with isolation. There are two ways to solve this problem. 1) add a rubber to the primary. The rubber circuit just dissipates the energy in the rubber instead of the transistor which reduces the stress in the transistor. 2) use a 2 switch approach. In the 2 switch approach the energy is returned to input power supply. The disadvantage is more complexity. 3) does not solve the problem but helps. Wind the primary and secondary on top of each other instead of side by side. This will reduce the stray inductance so you will get less energy in the spike. The main reason for using fly back converter is you only need one switch in the primary. Also you can add an extra winding that can be used to determine when the energy in the inductor has been depleted before turning the switch on again. This has a kind of a crude short circuit protection. At low powers the efficiency vs complexity tradeoff is worth. For higher power supplies like the ones on pcs the transformer is driven in both directions which solves the efficiency problem.

[@christianstrohmaier3675]

Francisco Shi Thanks for your thorough reply. Now I have some ideas to work on for my circuit.

[@shubhankarghosh]

Is it possible to build a configuration for DC 325V (from 230V AC) instead of 12V DC? I mean if I connect 325V in place of 12V

[@anuragemmadishetty2134]

Sir is the current on the output side same as the current we put in the primary ??? I tried the exact same project but I could light up only one led and not even a tiny motor Where I was supplying 2A of current in the primary

[@aserdasamazigh6316]

Excellente vidéo !

[@binukpremaratne6303]

Nice vid dude! One more thing, do you really eat all those 'ElectroBananas'?

[@ahmedatef6683]

Great illustration thank you, Could you explain how to me make it more reliable through feedback circuit the guarantees a constant voltage for a certain load?

[@GustavoPinho89]

9:22 I don't understand why two MOSFETs are being used in this power supply. It doesn't show on the schematic. Is the second one replacing the diode in the secondary part of the circuit?

[@d614gakadoug9]

I suspect he just doesn't recognize a diode in that package. Using two switches in a flyback converter is very rare. It is not unknown to use a FET as a synchronous rectifier for the secondary, but I certainly wouldn't expect one in a relatively crude circuit like the one in the video.

[@ronvaiz123]

Great project, very nice video!!

[@ronvaiz123]

Hi, What are the turn ratio of the transformer?

[@sciencetech9922]

,thks for your videos👌👌.I have planned to design 40w led driver ,can you suggest any to build?.

[@gtcollection6933]

Excellent explanation and awesome knowledge sharing, keep it up. #Suscribed!

[@piyushgupta6693]

why you used BJT with MOSFET as a switch?

[@jeffryblackmon4846]

Thanks a million.

[@rikvermeer1325]

I'm hooked.... HOOKED... this is the heroin of internet!! gimme mooooooore :P

[@saptarshisahoo5075]

I've a question. Why use two transistor? Why not a single MOSFET as a switch?

[@mmdnaderi7183]

first bjt transistor switches MOSFET on and off

[@ELECTRONOOBS]

Arduino can only apply 5V at the MOSFET gate. For that we need a driver. The BJT acts as a driver and applies 12V at the MOSFET gate!

[@saptarshisahoo5075]

@@ELECTRONOOBS So we need 12 volts for MOSFET to act make it a switch? below it it won't behave as switch. Am i right?

[@dannyperry8070]

Great video. Quick question. Can you use a Toroid as the trasformer for smps? What are the advantages and disadvantages of using a Toroid.

[@OtherDalfite]

Toroids work fine as a lot of smps circuits can use them. Main benefit of using non-toroidal is easier winding and more space for additional turns.

[@apurvmj]

What is the difference between coupled inductor and half wave bridge rectifier

[@raihangibran4219]

what is the primary to secondary number of turns ration for the coupled inductor?

[@ABINJPRAKAYIL]

Whats the maximum current rate it can handle? Can you help me with the calculation of current

[@adelashour3253]

Good, but what is the importance of the opto transistor, and the coil in the transformer that is connected to it

[@sangrambhumia9320]

I would love to see a video on how RC toys work .

[@techiesuraj7473]

Thanks for this beautiful video . And can you please make a video on how to calculate winding of the ferrite ring transformer for flyback dc to dc converter for car amplifier ???

[@RafiPrival]

can you make non-inverting buck-boost converter without trafo?

[@joshuamungasia4529]

thank you once more

[@carlosdelacruz6626]

Sir iwant to see how to asemble high voltage power suply sir. Im from philipines sir?ists ok to you sir. using flyback of television sir?

[@umargul5644]

Well done

[@karte2626]

Great channel!!! Do you have any video about an analog isolator? That is, the input ranges from 0 to 5 volts and the output follows the range input 0 to 5 DCV. I appreciate!!!

[@kenpeter3767]

Ordinary forward transformers feature simultaneous currents, and voltages that scale by rule of winding ratio. Flyback currents are purposely not simultaneous to break free of that strict ratio. Forward transformers have a strong slow inductance to avert energy storage in the core, but instead push current immediately to the secondary. Flybacks have weak fast inductance with gaps in the iron to quickly accept packets of energy into those gaps and release through a secondary diode on the other half-cycle. A flyback mis-cored as a forward would charge and discharge too slowly to be useful. A forward mis-cored as a flyback would present insufficient inductance to block low frequency current, and die a short circuit.

[@d614gakadoug9]

He seems to lack a fundamental understanding of how inductors work, and that once energy is stored in the inductor by the input circuit and winding, it is going to go _somewhere_ once the input side switch is opened. It doesn't "care" if the discharge is into 1 volt or 1000 volts, so the output side voltage isn't dictated by the ratio of the charge and discharge windings. Of course you *do* set the turns ratio appropriately because of other important considerations in a practical design. I note you use the term "packets of energy" which is exactly the same terminology I usually use in describing the way a flyback converter works. He misuses "buck" and "boost" when talking about the relationship of input and output voltage of a flyback converter.

[@LEO-xo9cz]

Thank you great video. Please could you explain the load resistor? Another question is do you just need a transformer with a DC output to power this or do I need a regulated supply? Thanks

[@Den_Electro]

Hi, friend. kzbin.info/www/bejne/aaPLiqZsi5Wnd7c

[@tylerufen]

Very good!

[@bashaaksema94]

Good timing im just working on an AC-DC converter. But mine just has a little more output 24V 20A lmao

[@mytechtrials]

Liked your video. Subscribec. Great content.👌👌

[@JasonRobards2]

What I'm missing from this is why the usage of a couple inductor instead of a transformer. What advantage does a coupled inductor have?

[@mikebond6328]

Flybacks run at much higher frequencies so create more eddy currents.

[@jisozaki]

Great video! Could you have replaced the Arduino circuit with a 555 timer circuit for the PWM?

[@robbieberry9700]

A 555 timer would work

[@Den_Electro]

Hi, friend. kzbin.info/www/bejne/aaPLiqZsi5Wnd7c

[@king-well-kong]

hi electronoob, may i ask you how much current it could handle? i mean the one you built for this video? and i have some suggestions since you and greatscott are into electronic, and you two are the easiest to understand. how about making current booster? or at least some explanation ?

[@ELECTRONOOBS]

I'll place taht on my to do list!

[@king-well-kong]

@@ELECTRONOOBS thank you, appreciated it 🙏

[@patprop74]

Very cool, now can you show us how to make one using transistors as the switch ?

[@ivarnordlkken8082]

Isn't that what he did?

[@lorenloren2259]

Wow now I get it....mister could you help me a link to the 12v schematic...my phone has issues when I screenshoot

[@abdelwahidkheloufi6705]

Sir . I need help . I have 1 memory about flyback and make simulation in Proteus . I do it but I didn't see results . Can u help me if u want of course

[@stephanc7192]

Isn't it a transistor and a diode on the smps? I didn't spot the output diode. Good video

[@krishnendumathur982]

Yes, it is a common cathode diode in a TO220F package for better thermal characteristics and current handling ability.