300 amp power supply

That's coupled inductor SEPIC. I'm using coupled inductor polyphase buck. Different beast.

Regards, Allan

What happens if you use a 220uF X7R instead for that?

--

John Devereux

Your costs go up a little (not that cost is an issue for this design).

Where do you get them? I can find X5R and X6S, but not X7R.

Allan

On 21 Sep 2015 13:30:31 GMT, Allan Herriman Gave us:

snip learn to SNIP

Use mica.

hello,

I finally received more details from my client. it will be installed in a vehicle with temperature ranging from -30 to 45 celcius. The size is... don't know if its doable... 10" x 7" x 3.5" yes in inches not in feet.

18vdc input 14.5v dc output at 300 amps.!

thanks

K

I just looked for a ceramic equivalent to the EEF thing posted on Digikey. The chip ceramics were a bit cheaper in fact so I was wondering what the point was of the larger, lower voltage "Al-poly" types.

Well there's this but that is cheating (and silly)

I could have sworn I found X7R there this morning but they have "vanished" so I guess I made a mistake. Just X5R and X6S as you suggest. Still, might be OK for some applications.

--

John Devereux

Can you provide a link to a 220uF mica capacitor?

would be the size of a house

NT

Look, if you want quality you have accept a few facts of life. Lets have no more of these wimpy surface mount things, do it right!

--

John Devereux

On Mon, 21 Sep 2015 07:48:51 -0700 (PDT), captoro Gave us:

Still no mention as to what the juice will be feeding. If all it is is a battery, then design parameters and requirements change significantly.

On Mon, 21 Sep 2015 10:14:18 -0500, John S Gave us:

You make a parallel bank, idiot. Provide yourself a link to some common sense.

Obviously. I didn't mean the topologies were the same, just the inductor use.

Coupled inductors' peak current advantage in a polyphase buck would come from being able to pump more flux into the discharging inductors even while they're discharging, reducing i.ripple.

Cheers, James Arthur

You are an imbecile.

The source is an alternator outputing 14.5v to a battery bank.

K

Huh?

You previously stated...

"hello,

I finally received more details from my client. it will be installed in a vehicle with temperature ranging from -30 to

45 celcius. The size is... don't know if its doable... 10" x 7" x 3.5" yes in inches not in feet. 18vdc input 14.5v dc output at 300 amps.!

thanks

K"

If the "18V" is actually coming from an alternator then regulate via the alternator, solution is trivial, low dissipation. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

that doesn't make sense. If the source is 18v from an alternator that would certainly change the requirements. Time to stop trolling & state what's going on.

NT

They seem to top out below 100nF, although no doubt there are bigger ones somewhere. The 91nF ones are ~$50 each

You need ~2400 of these in your bank. The good news is that in quantity the cost comes down to a more reasonable ~$40 each so around $100k total per system.

Or you could use the $0.50 Al-poly (or X7R etc).

--

John Devereux

Gotta watch the voltage coefficient for those dielectrics. Still, it's not a problem if you know about it.

For this particular design I have a mix of ceramic and Al-poly caps on the output. The total capacitance is over 10mF. I use a mix of types to get a low impedance over a fairly wide frequency range.

This is also the first design where I've had to take the Cu plane resistance into account in the DC/DC loop stability calculations. Sure, nothing can go wrong! As part of that I wrote my own finite element solver to calculate the plane resistance around the caps and the BGA. The swiss cheese effect from thousands of anti-pads has a nasty effect on resistance.

Allan

My clients says the alternator gives anything between 16 to 18v dc. And ma x 341 amps but would most likelyt produce 200amp. So no i cant hooked mysel f directly to the alternator. It is a prototype so no need for ceetificatio n.18vdc input and steady 14.5vdc output 300amp capacity. I was thinking about one IGBT that can run up 600 amp...

K