EEVblog #110 - Let's Design a DC to DC Switchmode Converter

[MiShO10O0O]

Dave ,, Please can you help me converting 48 Volts to 12 volts ,, All switching regulator ICs have a maximum of 40 volts operating voltage ! what should I do ?!

[TrollingAround]

1 person wanted to be one in 2^15

[thenerdyouknowabout]

Soz..... That was really easy, thanks save, like you vids, thanks a bunch!!

[thenerdyouknowabout]

That

[Firehowk]

google MC34063 calculator if u are lazy like me ;)

[123456789robbie]

your shirt is the coolest thing i've seen in ages. that is all.

[THEtechknight]

i actually repaired an infocus projector power supply that used the MC34063 for the 400v boost converter PFC circuit. it had failed.

[bcsupport]

To step down Vin to 3.3v, should Vin below 5v work ok ? I try using the online calculators with Vin = 4.5v and Vout = 3.3 but it doesnt seem to work right. Also when I turn down my bench CC/CV below 5.0v, the Vout drops way below 3.3v

[bcsupport]

You should do a tutorial for Step down mode

[leeYT321987]

Hey Dave. I just wanted to say that you are freaking AWESOME! I'm somewhat of a beginner hobbyist. I just cracked open a car charger someone gave me, searched the chip (mc34063), and BAM -- Dave's got a ~40-minute, step-by-step video all about how to design for this chip!!!! So cool you are. You've taught me so much. If you were here, I'd shake your hand. Thank you 1000 times. I love your attitude. You are a pretty cool guy. My love to you and yours. Have a wonderful life!

[EEVblog]

@leeYT321987 Glad you found it helpful, thanks.

[Rubdos]

Only negative feedback. FTW :D

[DanFrederiksen]

good stuff. I think a variable switchmode 30V 10A supply from rectified mains would interest many. get into the 90s of efficiency

[HillOrStream]

In the intro to this clip you refer to another video that I'm having trouble locating. Can you put a link to it in the description for this clip? Thanks.

[EEVblog]

@HillOrStream Annotation and link added to the video. It's #90

[HillOrStream]

@EEVblog Thanks Dave, I was trying to refer to it elsewhere. It was one of your best, IMHO.

[bodziobran]

what about dc-dc converter with dual power output transformer ? are the calculations the same as per step up way ?

[raduigret]

Thanks for this video Dave!

I'm using MC34063A as a step-up from 12V to 36V to power-up multiple high power HB LEDs, using this MC34063A online calculator:

bobtech.ro/mc34063a-online-cal­culator

[thebornguy]

y:

Im a studetn of Electrical engineering but also ive started to make experiments on my own and i want to purchase a small dual output dc power supply or something preferbly not to expensive is just for conducting small experiments i wonder if u could recomend something thank you my best regards and congrats on the blogs.

[xbr37fn2g6k9]

THX! :-D

[brizleciderarmy]

Would this work with negative voltages or should i be looking for an alternative version of this IC? I am looking to achieve -9volt to -12volts.

[adamdmer]

Great video! Thanks, Dave.

If you were designing a step-up to run a string of white LEDs off alkaline batteries, would you design the SMPS for the normal battery output of 1.1 to 1.3 V per cell, or would you design the SMPS for the fully-spent battery output of 0.8 to 1 V per cell ?

[fingerboy18]

I actually like data sheets with lots of formulas. It makes your application more specific.

[ashelyg16]

Great vid. I am building this exact circuit and your video really helped. Trained as a chemist so only took two courses on EE. You made it easy.

[Chimpalimp1001]

I love your shirt so much! I am an electronics newbie, so forgive me if this is a rather lowly question. I noticed that you rounded a lot when choosing your circuit parts. I also understand that inductors are rather large and having too many on a circuit board is inefficiency in space. But for your capacitors, and hell even if you had some bad resistor values, couldn't you add caps in series and resistors in parallel in order to get better values, or is it also inefficient in space?

[EEVblog]

@Chimpalimp1001 Caps and inductors have a large tolerance anyway, it's not that critical.

[mihailtalevski]

this guy has an awesome t-shirt!

[cowcrusher]

Where can I get that shirt? haha

[criscros7]

Good video, as always.

To make your lives easier: The best MC34063 calculator I could find (after 10 secs of googling and 3 mins of trying some of them out) is the one by rau-deaver. It's only for the step-up config, though, but there are more (typically less detailed) online calculators. The one on nomad.ee has the advantage of optimizing both R1 and R2 automatically. Another one is dedicated to Dave Jones. :)

[MonkeyFCoconut]

Great video dave! I've actually used the MC34063A forever in just about all of my designs. It's a great cheap, and it's cheap. If you want higher frequency though obviously it has a limitation of only 100kHz as you mention. I made a nice spreadsheet for calculating all of the values if anyone is interested.

[furman22]

Very cool-- I love how you actually go through everything and explain each step-- very entertaining-- what is your take on the AX3022 chip?

[mrmatz408]

What's the device that you used to adjust the load (the one that has the current output display)? I'd like to get one!

[EEVblog]

@mrmatz408 I explain it in a previous blog on dummy loads.

[detectiveinspekta]

I'm about to test using a TPS62203. 3.3 V output with ~95% efficiency. Using it for a GPS tracker, will be interestings how long I can make the unit last.

[fingerboy18]

Hey Dave. I need to design a power supply with the best regulation possible. Keep in mind that it is for a preamp tube. With a standard capacitor network, the ripple is too high. I have attempted to design a Pi Filter (CLC), but it was unsuccessful. Are there any resources you can share? Thanks; greeting from the USA!

[SLY3001]

Regarding the Toff it should be 3.7us will this be any significance?

[corester123]

Got any suggestions for more advanced applications, as for me I'd like to design an off-line buck converter to output 12v. The hardest problem for me is figuring how to power the logic circuitry without a secondary power supply(kinda defeats the purpose of the buck)

[electronicfanatic1]

what is a current sense resistor? and where can i get one?

thanks!

-EF1

[EEVblog]

@electronicfanatic1 It's just a regular resistor (usually low value) that happens to be used to measure current. Nothing special.

[davidsfc9]

@electronicfanatic1 also known as shunt resistor  sometimes

[MrTranxistor]

what is a "Shocky" diode?

[fingerboy18]

@MrTranxistor A Schottky diode is a "fast" diode.

[MrTranxistor]

@fingerboy18 ty sir. i had no idea of their existance!

[dvu90]

@MrTranxistor

It's a diode with low forward biased voltage drop.

[ivaneduardo747]

@MrTranxistor It is a type of diode that can be used for very fast switching and has a very low forward voltage. Normal diodes have a limit on the speed they can switch, Schottky diodes are much faster.

[Nadrealis]

@MrTranxistor Shotky

[coilsinamotor]

lol mate ;)

[uN1Qu3DZ]

@toffer1220 do read. if you don't understand something, let me know. there are a few inconsistencies with the formulas in that book... took me a while to figure certain things out. however i think they are intentional, as they encourage you to look back in previous chapters to find the formula you need. one more thing. when calculating transformer wire diam, use 7.75A/mm^2.

they recommend 3.5, that's over-engineering. in the real world you get away with less. the chinese do it all the time.

[uN1Qu3DZ]

@toffer1220 maybe you don't need videos. all you need is "Switching Power Supply Design, Third Edition". I learned pretty much everything i know about SMPS supplies from that book.

[uN1Qu3DZ]

or if you can't get any fancy controllers and don't want to use the tl494/uc3842, you can make your own. i built my own smps controller using a 555 and a comparator. it drives a 2-transistor forward converter putting out 400w. works in pulse skipping mode like some of the power integration chips. great efficiency, but you do have to varnish the transformer so it doesn't whine.

but it's got lightning fast response, and no compensation required because there's no error amp in the first place!

[PiezPiedPy]

Another Classic from Dave

[popsikas2]

Just found your blog, great stuff in it, keep it up! I have a suggestion though: in many of the cuts between takes you would do well to add a couple of seconds of extra pause, to let the previous words sink in. I wouldn't say the tempo is too fast to follow as it is, but the mind gets distracted if there's a continuous train of words without breathers in between :)

[chandin69]

just wondering what kind of knowledge is needed to actually design that chip.(not the fabrication but the circuit theory)

[Bushougoma]

Another great IC for low current switchers is the Topswitch series of ICs from Power Integrations. They are available in a TO-220 or DIP 4 package that includes both the PWM circuitry and a switching FET in one. I see these in lots of low part count standby power supplies.

[lartti83]

Have you ever considered working as a teacher? This is how one should teach power electronics in university or polytech, by real world examples not always the boring theory. Awesome tutorial!!

[The64BitGeek]

I love your T-shirt. "I only give negative feedback."

[nbsr1]

Dave, do you know any DMM, which can measure both voltage and current simultaneously and calculate power? Or, a DMM that can be tied to others and perform some calculations (like efficiency in your example)?

Manual measurements and calculations work well but they are a hassle when you want to interactively tune the circuit to the best performance.

[ubuntututorials]

Shocky diode, I've never heard anyone called them that, I thought they were called "scotticky" diodes...

[emactan]

Equations galore. Yum!

[RRROBERT1990]

Excelent job on explaining the formulas!

[DagGirl]

The shirt, DO WANT. Need to stop spending on expensive meals and get your shirts!

We're up to switch-mode ps's in two weeks. Exam on wednesday for basic power supplies, then we move onto the specifics Very easy subject, We're doing well.

[EEVblog]

@DagGirl Power Supplies is a pretty cruisy subject!

[hugos31]

excelente video

[truhlikfredy]

Ohhh boy I want yours lab so badly :-) When you get electrocuted can I have it? Pleeeeeeeease :-)

[Schmiki24]

Wow I love your shirt!

[EEVblog]

@Schmiki24 It's for sale on my Merchandise page!

[philbx1]

Hey Dave, thanks much for the hard work you've put into this. Magic! I had some fun recently with a 34063 Oatley Electronics K207A LED kit using 6 LEDs. Works fine now, but took a bit of research which included speaking with Branko :-) BTW, I tried an 'online' 34063 calculator and came up with the following: Strange value for Ct for a start... Ct=3028 pF Ipk=823 mA Rsc=0.365 Ohm Lmin=32 uH Co=68 uF R=180 Ohm R1=1k R2=11k (15V)

[gbowne1]

Sum Ting Wong?

[gzaloprgm]

Excelent video!

[TerminalJack505]

At 5:58 I swear Dave is saying "Wong Hung Low brand." LOL.

[EEVblog]

@TerminalJack505 One Hung Low is my favorite brand!

[rlewis1946]

Thanks for your many fascinating videos! We have all learned a lot of good stuff from your lessons! A Big Fan - RL Atlanta, Georgia, USA

[EEVblog]

@rlewis1946 Thanks, I still enjoy doing them!

[Dibblah1900]

Switch mode power supplies are great. However, board layout can become more complex due to the higher frequencies. I would love to see more information on board layouts - Lord_of_the_board.pdf seems a good intro to me, but I'm not very skilled in the art.

Cheers,

Allan.

[fknrdcls]

@Dibblah1900 Great suggestion, board layout with SMPS can become very important, especially when you start talking higher current designs.

[FoamPackingPeanuts]

Who needs to design a switchmode when you can pick up free sample converters from Texas Instruments? ;D

That said, great vid, Dave.

[scancool]

ripple thats a funny world, first time I heard it at my job I though they were just making up words

[lwhite703]

@576ito1080p I understand. Personally, I only use them when necessary, like when efficiency/dissipated heat is really an issue. Otherwise linear keeps things simpler.

[Nermash]

Magic:)

[lwhite703]

@576ito1080p Linear PSUs cannot "step-up" or "invert" DC voltages.

[000Ru000]

Brilliant vid as usual :)

[bswain9999]

excellent

[Gameboygenius]

@576ito1080p A linear PSU has a voltage regulator and heating element in one. :)

[lwhite703]

I've used the LM78S40 in the past, which has exactly the same specs as the MC33063 but in a larger package with a bonus (useless) opamp and diode. I always found the "buck mode" efficiency unimpressive with this chip (60-70%).

I've had better "buck mode" efficiency (75-80%) with the LM2594 from NatSemi "Simple Switcher" series.

[snik2pl]

great work!

[Chryseus8086]

Great video as always Dave.

How about a tutorial on winding inductors ?

[rafhit]

pls tell me that you are not recording that with that Canon 5D Mark II! because if you are, something is very wrong!

[killerman4ever]

@rafhit He isn,t. And the ugly video is because it hasn't fully processed yet.

[EEVblog]

@killerman4ever Correctamundo. Long videos like this take some time many hours to process. And Youtube is retarded enough to make it public before it's really finished processing.

[Knaeckebrotsaege]

@EEVblog you can set the videos to private or unlisted while uploading and set them back to normal when they've finished processing.

[killerman4ever]

Woohoo, waiting for this all day!