SMPS Buck Regulator Experience?

[Mike - K8LH]

SMPS Buck Regulator Experiences?

Does anyone have experience using any of the Buck regulator ICs available?

I'm interested in using something like the 1 amp' Micrel MIC4575 and the 3 amp' MIC4576 devices for distributing "cool" regulation along the length of a signboard matrix of 8x8 LED modules.

I'd also like to design and build a miniature plug-in 7805 replacement like the one Futz showed us recently for my assorted projects. I'm hoping I can build a few of them for much less then the $14-$18 price tag of the manufactured units.

My questions concern sourcing low esr capacitors and low profile power inductors.

Mike

 

[jpanhalt]

I have used the MC33167. It's cheap and can be configured as buck or buck/boost. I am using it for a 12 to 28 volt supply at 5 A with no problems. Do need heat sink. John

Edit: Had to get it from Mouser.

 

[ericgibbs]

hi Mike,
I have used the LT1074CT and the LM2577ADJ switchers, with no problems.

Why are you asking.?

 

[Mike - K8LH]

Hi Eric and jpanhalt,

My questions concern sourcing low esr capacitors and low profile power inductors. I'd like to make these as small as possible while still running 'cool' at 1 amp.

Mike

 

[ericgibbs]

Hi Eric and jpanhalt,

My questions concern sourcing low esr capacitors and low profile power inductors. I'd like to make these as small as possible while still running 'cool' at 1 amp.

Mike

Gotcha.

Low ESR:
https://uk.farnell.com/jsp/search/b...Ntt=Low+ESR+capacitors&Ntx=&_requestid=234645

68uH:
https://uk.farnell.com/jsp/search/b...001&Ntt=68uH+inductors&Ntx=&_requestid=234723

 

[jpanhalt]

Based on my experience, the MC33167 should be barely warm at 1A. I get by without one at 3A and resistive load. It is warm, but not real hot. John

 

[Mike - K8LH]

Hi John,

Did you use the TO-220 package with heat sink or mounted to PCB? Or, did you use D2PAK with certain number of square millimeter copper sink area?

Mike

 

[Mike - K8LH]

Eric,

Thanks for info'. I'll look for some of those parts at Mouser here in the states.

Mike

 

[jpanhalt]

I used the TO-220 case mounted vertically and a small, individual heatsink to conserve space. John

 

[Mike - K8LH]

Ok, I think I'm all set guys.

I've found the four parts I need to build and test a through hole version of the 5 volt 1 amp' regulator for about $2.95 at Mouser (two low-ESR caps', Schottky diode, and 68 uh power inductor).

Thanks guys...

Mike

 

[nickelflippr]

Also from mouser, 1.5A buck switcher from STM, L4962/A. Works pretty good, but ended up with giant low esr electrolytics and torroid inductor, and little under $10 in parts. Mind sharing your choices for caps and inductor? Thanks.

 

[Mike - K8LH]

If I understand correctly the 200 KHz switching frequency allows us to use smaller inductors and capacitors but layout and connections becomes critically important. MIC4575 Data Sheet

I wanted capacitors which were physically the same size so I modified the values a bit. Capacitance values are a bit higher but the input voltage is reduced to a maximum of about 20 volts. I'm hoping this will be fine for the laptop power bricks I use on my projects, none of which are more then 16 volts output.

Here's what I think I'd like to order unless you folks have other suggestions/considerations;

Mike

Mouser

[FONT=Courier New]D1 [URL="https://www.mouser.com/Search/ProductDetail.aspx?R=MBR360RLGvirtualkey58410000virtualkey863-MBR360RLG"]863-MBR360RLG[/URL]       MBR360 Schottky, 3a     ONsemi   0.30 ea
L1 [URL="https://www.mouser.com/Search/ProductDetail.aspx?R=18R683Cvirtualkey58010000virtualkey580-18R683C"]580-18R683C[/URL]         68 uh, 1.35a, radial    Murata   1.42 ea
C1 [URL="https://www.mouser.com/Search/ProductDetail.aspx?R=140-ESRL25V330-RCvirtualkey21980000virtualkey140-ESRL25V330-RC"]140-ESRL25V330-RC[/URL]   330 uf, 25wvdc, radial  Xicon    0.62 ea
C2 [URL="https://www.mouser.com/Search/ProductDetail.aspx?R=140-ESRL16V470-RCvirtualkey21980000virtualkey140-ESRL16V470-RC"]140-ESRL16V470-RC[/URL]   470 uf, 16wvdc, radial  Xicon    0.61 ea
---------------------------------------------------------------
                                                        2.95
Digikey
U1 MIC4575             Regulator, TO-220-5     Micrel   3.26 ea
[/FONT]

 

[ericgibbs]

hi Mike,
Whats the 'dc' resistance of the L1 68µH inductor.?

 

[Mike - K8LH]

Hi Eric,

Data Sheet says 0.07 ohms.

 

[ericgibbs]

Hi Eric,

Data Sheet says 0.07 ohms.

That sounds OK, reason for asking is that some of the smaller inductors can have a highish resistance,
which you dont want in a swpsu.

 

[Mike - K8LH]

Eric (and all),

Thanks for the tips. Micrel just notified me that samples are in the post so I guess I better order those other items.

Would anyone be interested in updates as I build and test smps regulator prototypes?

Mike

 

[Ubergeek63]

Does anyone have experience using any of the Buck regulator ICs available?
....
My questions concern sourcing low esr capacitors and low profile power inductors.

Mike

I am fond of the LM3485. It takes more parts but is much more flexible and inherently stable.

I ignore their recommendations and use a 10uF ceramic cap with a 22m series resistor and a 15uH inductor to get 12-25V in and 5V out. It uses more parts but accept for the external FET and diode they are all piddly little passives.

I am actually using the similar parts to get a very low power 3.3V out.

 

[Mike - K8LH]

Uber',

Thanks for the info'. I'll definitely check it out.

I'm really just looking for a "cheap" replacement for 3.3v and 5v linear regulators that overheat on a few projects that draw more than a couple hundred milliamps (from my 12-15 volt power supply bricks).

Mike

 

[Nigel Goodwin]

Would anyone be interested in updates as I build and test smps regulator prototypes?

I'd certainly be interested to see how you get on, SMPS regulators are really the way forward.

 

[Ubergeek63]

Well lets see.... at digikey $1.56 for the chip, $0.40 for the diode, $0.60 for the PFET, $0.86 for the inductor, and $0.60 each for the input and output 10uFs (unfortunately they are making you get 10 at a time )