LED drivers and itty bitty transformers?

Question

Ok, so I buy one of these led driver modules off of ebay, made in china -- they work great and will drive up to FOUR 1W power led's in series at 350ma.

The transformer in this thing is really small, maybe a half inch square. It has a 120v input and who knows what out.

Something I think I need to bone up on are DC to DC converters because this is where the magic lies, correct?

So, if this little transformer can put out 35ma, with a 1 to 10 conversion, I have my 350ma?

The transformer doesn't even get warm.

mkr5000 · Accepted Answer

Actually, looking at this thing closer, the transformer doesn't even look like it's connected to 120v via it's primary side?

Do they just manipulate the 120 right up front somehow and the transformer is?

Can someone perhaps give a simple overview to what may be happening? Thanks.

NT · Answer

like it's connected to 120v via it's primary side?r is?Thanks.Search terms: SMPSU, CFL ballast.NT

Tim Wescott · Answer

Try Googling "off-line power". It's been a while since I looked, but when I did there were single-chip + a few discrete solutions that went from 120VAC power down to +5VDC or whatever.

I _think_ the popular way these days is to go with a capacitive divider down to some lower AC voltage, then rectify, then do a fairly standard (but _cheap_) switched-mode converter to the output. But, as I said, it's been a long time since I looked.

gregz · Answer

I bought a bunch o 350 and 500 ma converters. The only problem, my housebuzzes with interference I detect on the fm band. I need to fix this.Greg

josephkk · Answer

look like it's connected to 120v via it's primary side?

transformer is?

Thanks.

Perhaps you have a power factor controller feeding the transformer, a few passives, a rectifier (maybe a bridge) and maybe an opto and a few passives for feedback.

?-)

LM · Answer

k like it's connected to 120v via it's primary side?

er is?

Thanks.

First I found, see:

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There are milloins of these. All have a diode bridge and a high voltage switching regulator IC feeding the transformer. Transformer is small because the frequency is high.

LED drivers and itty bitty transformers?

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