Author Topic: MC34063 Buck controller seems too cheap to be true?  (Read 701 times)

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Offline Faringdon

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MC34063 Buck controller seems too cheap to be true?
« on: May 16, 2022, 04:23:35 pm »
Hi,
We need a few Low power Buck SMPS’s…..200mA max output…
12v to 5v
24v to 16v
24v to 12v
24v to 5v

……so we decided to make a little Buck PCB out of MC34063 controller as attached.
This all seems too easy to be true….is there some issue with the MC34063?....its only on/off control.
Its literally just a comparator looking at the vout. Plus sense resistor which we will change for each case of vout.

MC34063 datasheet
https://www.mouser.co.uk/datasheet/2/308/1/MC34063A_D-2315484.pdf


 

Offline ledtester

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Re: MC34063 Buck controller seems too cheap to be true?
« Reply #1 on: May 16, 2022, 04:30:48 pm »
The MC34063 is an old part dating back to the 80's.

https://electronics.stackexchange.com/questions/78116/mc34063-switching-regulator-ic-when-was-it-introduced

Update: Dave did a video on the chip about 12 years ago:

EEVblog #110 - Let's Design a DC to DC Switchmode Converter
https://youtu.be/qGp82xhybs4

He goes through the complete design procedure for a step-up converter which involves a complete whiteboard of calculations.

Near the end he briefly talks about the MC34063 vs other chips mentioning that they can be easier to design for:

https://youtu.be/qGp82xhybs4?t=36m17s

« Last Edit: May 16, 2022, 05:13:07 pm by ledtester »
 
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Offline T3sl4co1l

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Re: MC34063 Buck controller seems too cheap to be true?
« Reply #2 on: May 16, 2022, 07:18:36 pm »
Too cheap to what, what else would you expect from something so crude?

Most of the layout area and cost goes to caps and inductors, it's pretty awful.

And LDO might be as or more efficient, for some of those ratios.

For so many outputs I'd consider a multiwinding transformer, doing up ratios to get it right.  That or fewer buck regs with a few LDOs to fill in the gaps if reasonable, but that's probably just reasonable for 16 to 12 here, and only if 12 isn't very much current anyway.  Or 24 to 16, if not much current (which might be?).

Tim
Seven Transistor Labs, LLC
Electronic design, from concept to prototype.
Bringing a project to life?  Send me a message!
 
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