On Wed, Jun 14, 2017 at 09:37:15AM +0000, alan.b.pearce@stfc.ac.uk wrote:
> > Byron believes (with tongue firmly planted in cheek) that switching
> > magnetics are a black hole for all knowledge and the source of all that=
 is evil
> > in electronics design. Russell has countered:
> >=20
> > "Do NOT be afraid of an inductor based circuit. With off the shelf and =
off the
> > net circuits and advice from here you should have no excessibely major =
[tm]
> > problems with the converter."
> >=20
> > So I'm here to put this hypothesis to the test. For my electric riding =
mower
> > project I see two switching projects that would really be helpful.
> > Both are based on the 48V 47Ahr Chevy Volt module that I bought to run =
the
> > mower.
>=20
> Just revisiting this as I saw a pointer to this device on a Circuit Cella=
r email.
>=20
> http://www.linear.com/product/LT8304
>=20

> Looks like it could do the job (I haven't run through the required
> charging rate etc. numbers though) and it has very simple magnetics and
> no opto.

> Precede it with a PFC chip to keep the input voltage within its maximum a=
nd all should be easy peasy.

> Also check the 'Other people also viewed' links at bottom for similar (po=
ssibly better) devices.

Alan,

Your suggestion really just reinforces my point. First the focus is still
off base. The control electronics really isn't the issue. Any number of PIC
parts has the required PWM, ADC, comparators, FVR, and the like to manage
the control side of things.

It's all about the magnetics. I pulled the datasheet for the part. As with
many other integrated solutions, there's a list of magnetics COTS for use
with the part. The closest for my application shows a couple of 1:2
flyback transformers for use in a 48V output application. The output
current is 300 mA. This is totally useless for a charging application.

Doing some more research I finally decided to go a different route. Instead
of trying to using a flyback or forward converter to downshift a high VDC
bus to the target, instead I'll go back to traditional 60HZ power
transformers setups and use a boost converter to get to the target. The
transformer will give me the isolation that we all agree is needed, and
complete tuneable boost converters up to 30A and 1500W are available online=
 in the
$30 range. I have a salvage UPS transformer that's in the 24V RMS ballpark
that can serve the purpose.

Once again the dastardly magnetics have foiled my plans again. It's
anything but easy peasy.

BAJ

>=20
>=20
>=20
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--=20
Byron A. Jeff
Associate Professor: Department of Computer Science and Information Technol=
ogy
College of Information and Mathematical Sciences
Clayton State University
http://faculty.clayton.edu/bjeff
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