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Topic: DC-DC Buck Converter high current usage when idle (Read 4268 times) previous topic - next topic

bratan

I recently discovered these awesome (on paper) DC voltage regulator breakout boards on eBay.
Size is so small, I can just solder to my PCB instead of LM7805 for example.
However looks like it might have been too good to be true.
I tested them and they suck unexplained large current even when there's no load (up to 60mA). This depends on the in and out voltage (i.e. when out is 5V and in is 9V it uses about 40mA, but this relationship is not linear).
These boards are based on MP2307DN chip, which in the datasheet states that it only uses up to 1.5mA of supply current.
Does anyone knows why it might be happening? I tested 2 of these so far, same thing...
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Wawa

Did you test it with a small load. e.g. 20mA.

Pololu claims 200uA idle for this micro buck converter.
https://www.pololu.com/product/2843
Leo..

DVDdoug

60 mA isn't so terrible....    That's like 3 LEDs...

As a general rule, switching supplies are less efficient at low currents (or no load) than linear supplies.   And of course, much-much more efficient at rated load.

And, what do you expect when you buy the cheapest thing you can find on eBay?   

weedpharma

It is all relative. A project running off a power supply from mains, this is not much. A project running off battery, this is huge.

Weedpharma

jremington

Thanks for the warning! I'll steer away from the eBay converters.

aarg

It looks a lot like the reference design. I have a hard time believing this. I would just go back and measure again, confirm your meter settings.
  ... with a transistor and a large sum of money to spend ...
Please don't PM me with technical questions. Post them in the forum.

Wawa

+1
9volt@60mA is >0.5watt.
Something must get warm/hot.
Leo..

DrAzzy

#7
Sep 02, 2015, 03:37 am Last Edit: Sep 02, 2015, 03:37 am by DrAzzy
I just measured one of these guys at ~5.3 mA quiescent current: (10 in 5 out)
http://www.ebay.com/itm/LM2596S-DC-Buck-Step-Down-Voltage-Adjustable-Converter-Power-Module-Regulator/331479380445 (I do *not* endorse this listing - I paid under $1.50 for mine)
and I got 11mA on a very similar one based on the X6009 (boost converter) 9 in 13 out
And under 5 mA from a much beefier buck converter (one of the 90/150 watt ones)

All el cheapo ebay ones.

It sounds like there's a design flaw of some sort in the ones you're using - either that or you're measuring wrong... 60mA quiescent current is frankly garbage for such a small dc-dc converter in the year 2015.

And yeah, something must be getting warm if it's drawing that much current and wasting it... what part is heating up?
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bratan

#9
Sep 02, 2015, 12:54 pm Last Edit: Sep 02, 2015, 12:57 pm by bratan
Lm2596 based based converters are great, I'vee been using them for years in many projects, but they are somewhat big :)
I'm sure about measurments, my bech variable dc suppky shows amps output, and I tested it with DMM in line. Didn't notice much heat, at least to the touch, but I'll inspect it tonight with my Seek thermal camera.
Weedpharma is correct, for battery powered project 50-60mA is huge...
Btw this thing also buzzes, not sure if its supposed to. Could be wrong or bad quality inductor....
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aarg

Btw this thing also buzzes, not sure if its supposed to. Could be wrong or bad quality inductor....
So it draws too much current and buzzes... Hmmm...

The switching frequency is about 450Khz. Of course, it is not supposed to buzz. I suspect your circuit wiring or layout. Can we see a photo?
  ... with a transistor and a large sum of money to spend ...
Please don't PM me with technical questions. Post them in the forum.

bratan

So it draws too much current and buzzes... Hmmm...

The switching frequency is about 450Khz. Of course, it is not supposed to buzz. I suspect your circuit wiring or layout. Can we see a photo?
See my first post for photo. Good point on frequency, human ear shouldn't hear it...
Xronos Clock - A talking arduino based alarm clock is now available. Check out xronosclock.com for pictures, source code, schematics, etc.

septillion

I'm pretty sure he means a self taken photo of your setup ;)
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aarg

That kind of behaviour usually stems from excessive load current. So please check that as well.
  ... with a transistor and a large sum of money to spend ...
Please don't PM me with technical questions. Post them in the forum.

bratan

I see. Well there's NO setup :)
DC-DC converter is connected to variable DC supply, output is not connected anywhere
Xronos Clock - A talking arduino based alarm clock is now available. Check out xronosclock.com for pictures, source code, schematics, etc.

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