What topology to use for building a car power supply?

[swede]

Car Power supply

Hello

I need to build a power supply for my car.
The V.In Range 7,2-18, multiple output V.Output 1=3,3V I.out=10A, V.Output
2=5V I.Out=10A, V.Output 3=12V I.out=5A, V.Out 4=5V I.Out=2A. Output power 200W.
I was thinking about using FLYBACK topology. But from diffrent places I've heard that that might not be the best topology to use, What are your suggestions?
I have also searched for some schematic/parts and descritpion with out any major success.
Found a Site (National.com)But I did not have any success there, as a responce to a email I sent they said "The best way to build multiple output power regulators is to use a FLYBACK topology. However for your requirements, the calculated peak current which would flow through a FET is about 100A! Our flyback converters are limited to only 5A maximum, while our FET controllers are limited to only 10A.
Even our MOSFET Drivers will not be able to drive such a big FET due to its high gate capacitance. "
So if any body have any suggestions on what topology to use and/or any good sites for schematic/parts, or any other helpful suggestions please let me know.
Thank you

 

[VVV]

Re: Car Power supply

The flyback is generally the choice for a multiple output power supply. Generally, however, the output power is limited to about 150W. That is because of the high peak currents, especially in the output capacitors and rectifiers (not as much in transistors). Since the highest power is required by a relatively high voltage output, 12V, that can make things easier on those components and you may be able to get away with a flyback in continuous current mode.

But probably in your case a better choice would be a coupled-inductor forward converter.
What are the minimum currents? What are the regulation requirements?

In a low input voltage DC-DC the transistor currents are high anyway. You will have to switch about 35A. This is common. It can be done with 2 or 3 paralled MOSFET's if necessary.

Please post for more help.

 

[swede]

Re: Car Power supply

Hello

I guess this is where my amateur status comes in, because I dont know what the min. currents would be.
The equitment I use in the car just states the needed volt and the needed Ampere.
I have a MP3 player for example that I use sometimes. It just states that it needs 5V and 2A.
So if that player could use a lower current then 2A I don't know.

I don't know what possibilites theree is to figure out if there is a lower current possibility for a item.
If there is I would really appriciate any tips on that.

If you have any other suggestions please let me know i really appriciate all the help I could get on this. Thank you for your suggestions

 

[VVV]

Re: Car Power supply

Hi

5V at 2A is really not a problem. Possibly the 2A is really a maximum value, but, again, this is not a problem, since the power is only 10W, so variations would not cause too much trouble.

What is the 12V@5A used for?

And perhaps the question I should have asked first is: do you require isolation?