The Most Versatile Voltage Converter you never heard of! The (S)EPIC Converter
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- čas přidán 5. 06. 2024
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In this video we will be having a closer look at the SEPIC voltage converter. You probably do not know it, but most small Buck Boost Converters are in fact SEPIC converters and for a good reason. I will show you how the SEPIC converter works, why it is "(S)EPIC", how you can modify it with a coupled inductor and how to make a DIY version. Let's get started!
Websites which were shown/mentioned in the video:
www.we-online.com/catalog/en/...
www.onsemi.com/pub/collateral...
www.ti.com/lit/an/slyt309/sly...
datasheetspdf.com/pdf/1096363...
datasheet.octopart.com/IPD088...
www.ti.com/lit/an/slyt411/sly...
www.all-electronics.de/wp-con...
www.digikey.de/en/articles/co...
www.ti.com/lit/ds/symlink/lm2...
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0:00 SEPIC Converter?
1:54 Intro
2:29 How does it work?
5:20 Advantages of the SEPIC
6:05 Secret Coupled Inductor Hack?
9:21 Which SEPIC should you buy?
9:49 DIY SEPIC - Věda a technologie
I once tried prototyping a 1A buck LED driver that operates at around 1 MHz on a bread board.
This ultimately drove me to begin my bachelor's degree in electrical engineering because I had no idea why the heck this just wouldn't work!
Today I do know why... =D
What wasn't working?
I presume that it might have been the frequency; but I still want to know!
@@After_Tech_Industries To be honest, I never actually checked what was the problem. So "Today I have some ideas why" would have been more correct.
I think the main reason was the high contact resistance in the bread board contacts along the high frequency, high current path. I think the losses there probably screwed up the feedback loop of the regulator.
Another probable problem was that the MIC2301 driver chip that I used has an integrated high side switch and therefore its SOIC8 package has an ePad at the bottom for cooling. The SOIC adapter board I used didn't connect to that, of course. I think it then also overheated way more quickly than I expected.
I was researching the different topologies to decide which one to design a low-voltage DC UPS around, and kept hearing that SEPIC is unstable against transient loads. It'd be interesting to see a video on how different topologies react to different types of loads.
Hey sounds like the situation I found myself in too! Surprised there isn't more commercial options around this given how often you'd think home users would just want an uninterrupted DC power source for their home network and other DC-powered electronics. My setup at the moment is a small server rack with a 15V DC PSU and a 12V Lead Acid battery (+ battery tender) with their ground connections tied. The output voltages are separated by diodes, thus creating a sort of "OR-ing" device. That gate's output is connected to a powerpole rigrunner so that I can split all my components to separate SEPIC converters to ease the change in load and to also not have a single point of failure. So far so good but then again I'm only running raspberry pi's, switches, and a router at the moment.
My experience is any SMPS will be unstable with transient loads. Go ahead and use one, but either have a huge cap, a battery or some other stable transient source to keep it from blowing out your electronics, or add a linear low-drop-out regulator at the end. It could even run saturated for low loss, but will prevent the voltage from going too high.
That said, I suspect this SEPIC is worse than most SMPSs.
Many power supplies are based on a dual control loop topology, with an outer loop with conventional voltage control PWM and inner loop based on current mode control. This tends to protect the power supply against transient loads, especially short circuits and the like. Something like UC3843 and like series of chips may be more stable with a SEPIC converter. There is a sense resistor in series with the source of the switch to control switch currents, and there is an outer control loop that senses the voltage.
@@chaosdragon6718 These are the reasons I moved away from SEPIC topology. I'm currently exploring flyback and push-pull, but stepping from designing buck converters to these more advanced topologies is pretty daunting.
There is also a four-switch buck-boost converter. Maybe look at BQ25713 for an example.
What I like about this design is the "self destruct" protection capability:
One of my biggest fears when using Buck Converters specifically is that, when the switching transistor fails, it will most likely go shortcircuit (which in buck converters means the full input voltage will get to the output) destroying the load with overvoltage. In contrast, this design will not only let the voltage go low but also may just blow a fuse or trigger an overcurrent protection.
This feature/bug is also present in synchronous buck converters: if one transistor fails, as soon the second one turns on, the whole thing will just go shortcuit and trigger a protection system before the output voltage can get high enough to kill the load.
But maybe I've too much of a green mind for a disposing culture society?
Your videos are truly informative. It provides me with a lot of electronics knowledge as a hobbyist. Keep going. Also get well soon. You are great, scott :)
Thanks a ton
@@greatscottlab I'm so glad that you replied to my comment 😊
@@greatscottlab what is the amps of this and could I safely use something like this with a 12 volts 20 watts solar panel?
Sure, they're very nice. But I think there's an error on the schematics presented for the DIY SEPIC (on 10:20): there's no connection to gnd for Q1 (and L2, C4, C5).
Another great video.
SEPIC converters are great for applications where the output power is low. For higher power applications, there is the two-switch non-inverting buck-boost converter. It is simply a combination of a buck and a boost converter. When the input voltage is higher than the output, it holds the “boost” switch open and modulates the “buck” switch. When the input voltage is lower than the output, it holds the “buck” switch closed and modulates the “boost” switch.
it will be priblematic in between, .....
3:00 your Bosch washing machine is done.
I don’t think I understand more than a small bit of your CZcamss but I watch and rewatch and even if I never understand I enjoy your drawings as much as anything. So clear. Your CZcamss are art.
Your videos are delightfully concise with surprising details and always inspire greater things
Ah yes another great scott video!
Awesome video,very informational about the sepic convertor!
Glad you enjoyed it!
Another great video!
What I always love , is the use of paper, pen and markers!
Great video Scott! I suspect your ferrite toroid had issues due to saturation, due to the uni-directional currents in it. Either add a small gap by using a multi part core, or go with high permeability powdered iron.
Some years ago I designed and built my own SEPIC converter, and used an off-the-shelf part for coupled inductors with one core. Before I built it, I actually did simulations of coupled vs separate inductors and it helped the ripple out a bit. Once built, it worked quite well. My board also included a Ćuk converter which is basically when you take a SEPIC and swap the placement of the second inductor and diode, resulting in a negative voltage with very similar specs. Made for a nice stable+versatile bipolar +-12V supply.
Hi Scott! Thank You for all the GREAT videos!! :-)
I love using SEPIC in my designs. The biggest benefit is that they are inherently failsafe, there is no fault mode in which the input voltage can be on the output. Also if you need positive and negative rails, you can use the same regulator chip for SEPIC and inverting.
C1 fails short.
There is a chance yes, but if I remember correctly from Siemens’ SN29500 the chance is relatively small.
And then you can split up C1 to make the design even more robust.
Great shot, Scott!!! Thanks.
Although I'm not an electronics guy, I like your videos a lot, because they are very informative and understandable.
I'm looking at the schematic with coupled inductors and it appears if you remove the coupling capacitor you end up with a flyback converter. It just goes to show that all the different DC-DC converter topologies are actually very similar in operation.
You have some of the best electronics videos.
Thanks :-)
Excellent video, Scott!
Nice video. I've been using these buck/boost converters in my projects for several years. They work great, and allow you to use almost any DC cube power supply without worrying about input voltage.
Also USB 1-30V CC CV converters are using SEPIC topology. They are really handy to use, but the efficiency is about 60%
Love your videos, it’s so simply explained yet very informative,
I wish you could make more videos of coupled inductors since it’s a rare topic on the internet!
Your definitely one of the most intelligent you tubers lol. Live your channel. When I finally get my parts replaced and back too work I’m definitely funding your channel lol. Ty for your time and research my friend.
Awesome! Thank you!
@@greatscottlab Next project Cuk Converter pleaseeeeee
Outstanding videos in every aspect AGAIN.
I truly respect you.
Thanks mate :-)
I would love to see a video about vacuum flourescent displays!
It’s kind of amazing that buying two inductors is significantly cheaper than a single coupled one. I suppose there’s just not a big enough market for them to compete on price, huh?
Super cool video! Especially the DIY circuit at the end.
Winding a single is much easier than winding a dual with most winding machines.
Informative as always! Thanks mate!
Eagerly looking forward for next episode of "Diy or buy" as frequency modulator ( FM radio)
So informative , Thanks a lot man
Thanks for All your video's.
I have a SEPIC converter in Simulation program LTCad XVII.
But NO matter WHAT i do, the current through the LOAD is Reversed.
Till I saw this Video ! With D2 connected between Vcc and GND.
NOW it Works ! Great Scott !
Sir i love your hand writing
Fantastic video, dude! Thanks a lot! 😃
I'm definitely going to look around for those!!!
Stay safe and creative there! 🖖😊
Thanks! You too!
This is without doubt a very useful project
Glad you think so!
I have alot of experience with SEPIC and Cuk converters. Coupled inductors are great. They can be more efficient (alot of variables there though), they have better dynamics (dual inductor SEPICs and Cuks have some high frequency resonance that can make compensation harder), and the overall solution size can be smaller than for dual inductors. What I've seen is for name brand (like Coilcraft and Wurth) inductors, prices are comparable between two singles and a coupled. But the market for singles is bigger, so its easier to find other manufacturers of singles. Also, worth pointing out that I've heard Dr Cuk is adamant that a Cuk converter built with a coupled inductors isn't really a Cuk converter.
lol "cuk"
@@Blox117 It's named for en.wikipedia.org/wiki/Slobodan_%C4%86uk . Funny name perhaps, but he's Serbian, that is his name, and that is indeed what it's called.
@@Blox117 Apparently it's pronounced 'chook'
@@triffid0hunter oh i see, there is an accent mark
dude, the sepic is noesing as fk, but i have to use it, how to reduce the ripple to 5mv under 12v at 3a? i have tried everything........rc lc re apsorbtion, comm choke, what i did wrong? it keep around 100mv at 1a ar 12v, i cant knock it down further.......
For higher currents, a 4 switch buck-boost will always be the better solution.
SEPIC (as well as inverting CUK type ) switches VIN+Vout on its switch node and carries the large du/dt EMI problem. And you switch more current than Iout. That to a much larger Hot loop which includes the SEPIC coupling capacitor. In essence, you store the complete transfer energy in the inductive components so those inductors have to be sized that way.
You generally need lower inductance if you used a coupled inductor. It isn't just the efficiency but also space reduction :)
Very good video Mr Scott.
I found a moderately high power (5a or 60w) buck/boost converter. What I found was a decrease in efficiency, increase in heat. My aim was to power 4g modem/router on boats, which operates in high temperatures (on sea, on summer, in Turkey). Boats are like cars, while engine is running voltage contains lots of jitter due to charging alternator. And just like cars, in small boats there is not a service battery, which means while engine is not running voltage is 12v. While starting the engine, voltage can drop down to 10v. While engine is running, there is a lot of noise (or jitter) and voltage is 14.4v.
My solution was to use two coils, then a group of capacitors then a boost converter (increases the voltage to 15v) then a buck converter (reduces the voltage to 12v). 🤣😂 This devides the heat dissipation, reduces the jitter and just works...
But in lower power applications (like 1-2amps) buck-boost converters works very nice.
This is a bit silly because the 4g modem/router internally has buck converters, which you obviously cannot get around, so you are forced to use this roundabout way.
High freq, and highly integrated GaN buck-boost would have worked for you well, but this tech is not very widely available yet, and probably more expensive than chaining two very simple converters like you have done.
I think you can build a boost converter circuit on a perfboard but you must put the components much closer together, the distance you use wouldn't work properly on any PCB type I think. All datasheets of switching power supply IC's are always hammer on that you must keep the loops as short as possible.
Awesome and very well explained. Great Sunday afternoon entertainment !
Awesome :-)
Perfect video! Thank you!:DDD
Great video Scott. I learned a ton. Next week your prototype PCB will be shipped by your sponsor JLC PCB I guess ;-)
I actually built a SEPIC converter on a perfboard recently. It can output up to around 50W of power and comes with an efficiency of around 80-85%. Anyway, great and educational video!
Hey, your voice sounds like you are (recovering) from sickness. I wish you the best!
nice, often i see boost buck and sepics being combined IC
that efficiency seems low tho at 60% a LDO may be better ( if it is lowering)
Also maybe make a video about the energy efficiency of all those converters .
thx for ur videos. will watch
Nice work👍
( 1:21 & 6:22 ) I have used a SEPIC voltage converter that uses a coupled inductor and it has some decent efficiency and also has some protection features which is nice. The only concern I have is the EMI it might be producing specially I used mine on an audio amplifier build and it has some weird issues "sometimes" specially on its aux mode, might have to some tests on it to confirm those thingies.
Very enjoyable video. Best regards Chris
Glad you enjoyed it
The SEPIC buck-boost design is more elegant than I expected it to be.
Amazing channel, super video!!
Thank you very much!
Great video. Can you compare the SEPIC with the non inverting buck-boost to see which one is mor efficient? Thanks.
Nice job 👍
I'm thinking the Prof. Slobodan "Cuk" converter deserves a thorough review. Somewhere I have my first power supply kit I built, a SEPIC-Cuk split rail design to emulate a low power computer PSU and I'm trying to recall what specifically. Man, I forget, seems like something maybe SDR related though I forget. Neat design.
I'd guess that a specific boost or buck circuit is more efficient, to take a simple example in a 12V to 24V boost, half the output power is coming directly from the input, while it's a bit less than half in a 12V to 5V buck
TL494 is awesome choice.
You can even make ~240V DC boost to drive vacuum tubes. Not recommend for beginners, but you can check out Mr Carlson's Lab.
What happens to efficiency if you make it synchronous? I’d think you’d get it way more efficient. I’d love to see more videos on boost/buck with ultra high efficiency for sure.
Synchronous 4-switch devices are much more efficient and can handle much higher currents. Of course the down side is that they are much more expensive and are also becoming quite hard to find.
My preference for stable voltages with very little ripple are ones based on the LTC3780, the output is so stable that I have very successfully used them for mobile radio, something which is near impossible with most non-linear converters. I realised early on that Sepic devices would not be adequate.
@@chrishartley1210 ya a full bridge is a solution but the problem with full bridges is that they require p channel high side which means you can’t use ganfets. I’m wondering if sepic with the diode replaced with another fet woold get you to n channel nirvana.
@@jameshancock The 3780 (and 3789) drives 4 N-channel MOSFETs.
@@chrishartley1210 wow. Gotta see how they do that because a pump can’t work so how are they keeping the top fets open 100% of the time?
I am your big fan great scott
Very interesting. Thanks for the content.
My pleasure!
Interesting. Do you have a video on that device with the display and the fan/heatsink?
hi scott did you make board with automatic li on charger with load sharing or power path function ? powering your project automatic while its connected to 5v usb and without damaging battery
Hello from Georgia, USA! I really appreciated this video. I do have a question that I would like to ask. I'm adding heated seats, grips, gloves, and primary clothing layers that will run off of my bike for cold weather riding. The bike has very little extra power so I'm changing all of my lights to LED and I want to use a solid state timer for the signals rather than simply adding resistors to prevent hyperflash.
Most of the heated element controllers use a resistor for the lower temperature settings. It seems to me that I could use one of these boards to control the temp and actually conserve amps by using a lower setting If my gauge showed a constant draw on my battery rather than a 2a or so charge.
Am I right. I'd use the FP5-139 to get the most out of each amp put out by my charging system.
awesome. use this all the time. finally learned how they work
Great to hear!
The LM based ones works fine down to 3V the XL based starts to have issues below 3.8 volts, don't use it if you are using an input range below 3.8V.
I would have thought the two coils in close proximity would couple anyway. Perhaps not as tightly/efficiently as two windings on the same ferrite ring, but... it's something?
Cool video, thanks as always! =]
No problem!
nice job
Have you considered using a synchronous switching configuration rather than the diode? Perhaps that would give you a better efficiency payoff than using the coupled inductor.
using a transformer ensure 5percent increase, lossen coupled one gives anther 1percent boost, a llc typology needs pmos, or bootstrap, whichs means bad, really bad, especially in boost condition.......
Nice video
Hello Scott, how you made your beginning perf board logo? You connected your LED's in parallel or series?
Thanks for the video, it was very interesting to see a different approach, perhaps you can help me with a problem, I want to make an 18650 12v power supply to run an emergency LED light, so do I put three 18650 in series to give me my 12 volts or do I put my 18650 batteries in parallel to give me 3.7 volts and boost that voltage to 12 volts, any suggestions for the best method?
Thanks, Bob in the UK
Where do you find the silver copper wires you use? I haven’t be able to find them for years now.
Awesome!
Thanks man
You're welcome!
What a great information 😯😊👏 thanks
Glad it was helpful!
@greatscottlab Do you know if aliexpress has any variable power modules that can be controlled though i2c.. I want to make a i2c controlled bench power supply.
Maybe modify the Dave Jones PWM supply, using a i2c PWM servo controller
and ADC feedback to make sure the output matches what you asked for..
and make a triple output supply
Moin,
I have a question regarding buck/boost converters.
I have one of these standard 9(or 12, or 24)V DC Plugs. But if I hook them up to a buck boost converter, I can change the output. The output voltage stays constant at 9, 12 or 24 volts.
The converters are otherwise okay. I can change the output of these fancy USB c PD boards, but these DC plugs just don't work :(
el circuito que armas ????? esta subido en algun lado? quisiera ver el feedback de tension
Very informative video, congratulations!
I can't find the link for your chosen convert, can you give me here. Thanks.
I've got some fiber optic cable laying around, how about a video showing some potential uses?
I'm designing a power supply around 60v. Will this design be able to withstand 60 volts? What changes are needed to get there?
recent day I made my own sepic converter with xl6009, two 47uH inductor and a 1uF capacitor. It can deliver much more energy than I think and blow up my AO3400 and AO3401. and another interesting thing is it cannot work with usb because some usb power connection is poor and voltage can drop to 3.5V so the chip will not work properly
Is this commercial Buck converters are coming with close loop control (I mean, is it change its duty according to the change in output voltage? As we know, the output voltage may change with change in load. Please, give your thoughts.) Thanks, in advance
That sounds like a constant current/constant voltage (CC/CV Buck) converter. The LM5117 is just one example, but I bought some cheaper ones from Amazon years ago because I needed constant current control for running LEDs. They use feedback loops to monitor current & voltage.
They use the smaller coil packages mainly for size savings and there has been an artificial standard for such converters because a few companies in China did massive runs pumping out near to a half million units and resellers flooding the markets like Amazon and eBay......they become so common that they just get copied
very interesting video
I need that buck boost converter, but I need a very small one for a drone, do you a circuit diagram?
I would like to know if there's a current limit to them or can I send alot of amperage form one?
I was wondering if I could use a filter choke as a coupled inductor?
Danke!
Thank you very much for the support :-)
Hey GreatScott! Would it be possible for you to make an adjustable 100 watt output RF amplifier useable frequency range of 7mhz to 30mhz with the input being 5-10watts. Would love to see a video on this as i’d like to make a diy amp for my ham radio.
Love your channel!
qestion: can you make a cheap/ceapish "garden light mppt "low Voltage battery/supercap?
Great!!!
Damn... the comment section is moved again.
As usual, great content, Scott !
Wish I could do something with this but nah, not even my profession neither my job, still watching this xD
Get well soon brother ❤️🔥
My voice is already much better :-) Thanks.
Great.. too much information..i learn new..thanks a lot for such a good video..
I made a boost converter using a 555ic and an irf540 mosfet. I used a sepic winding of 150uf. I could get 9v input 99v output. It was fun. I'd love to know what you think of it.
555 ic in not efficient for this type of circuit
Good Video! 👍
Thanks!
Any improved eff if you ran 2 buck boost converters in parallel to one load?
would be awesome to see your thoughts on the sw2303 with power distribution
Very good video Mr Scott. please what is the link for the module you recommended?