Forums

LED drivers and itty bitty transformers?

Started by mkr5000 October 17, 2011
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.







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.
On Oct 17, 1:53=A0pm, mkr5000 <miker...@gmail.com> wrote:
> 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 transforme=
r is?
> > Can someone perhaps give a simple overview to what may be happening? =A0 =
Thanks. Search terms: SMPSU, CFL ballast. NT
On Mon, 17 Oct 2011 05:53:28 -0700, mkr5000 wrote:

> 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.
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. -- www.wescottdesign.com
mkr5000 <mikerbgr@gmail.com> wrote:
> 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.
I bought a bunch o 350 and 500 ma converters. The only problem, my house buzzes with interference I detect on the fm band. I need to fix this. Greg
On Mon, 17 Oct 2011 05:53:28 -0700 (PDT), mkr5000 <mikerbgr@gmail.com>
wrote:

>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. 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. ?-)
On 19 loka, 07:10, josephkk <joseph_barr...@sbcglobal.net> wrote:
> On Mon, 17 Oct 2011 05:53:28 -0700 (PDT), mkr5000 <miker...@gmail.com> > wrote: > > >Actually, looking at this thing closer, the transformer doesn't even loo=
k like it's connected to 120v via it's primary side?
> > >Do they just manipulate the 120 right up front somehow and the transform=
er is?
> > >Can someone perhaps give a simple overview to what may be happening? =A0=
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. > > ?-)
First I found, see: http://cds.linear.com/docs/Datasheet/3799f.pdf 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.