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Help me with 12V to 48V DC-DC Converter

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laurianus:
I have to be more specific

1. I read the data sheet and I know that it's says there it can work on output with maximum 1.5A. But I also know that if you use right voltage, current, peak current on external components (mosfet, inductor, diode) u can theoretically (use formula) get infinite voltage and current. But practically, after a limit u will not find any external components with those characteristics. Another problem is that the energy loss (efficiency<100%) is transformed into heat. More power/voltage on output -> More ... more power on input and more heat. This and all StepUp controllers are actually a timer for switching, a comparator to regulate voltage and a short circuit/temperature protection, all put together in the same IC.

2. I want this solution to be a custom design so that I can integrate it in a PCB. I want to find all the components(the inductor might be a problem) used for this solution on the market, not to be custom made. What I need can be started 1 minute before this single big spike (aprox 400 ms up to 10A - theoretically I need 12 spikes at 8A for 15ms with 5ms in between, meaning a total time of 180ms). During this spike voltage and current can drop(at the end of the spike it can be 36V and 5A). I know I can use more and bigger capacitors but it's not my preferred solution.  I want to use maxim 2, but preferred 1, at 4700uF/50V.  If I buy mass products of this StepUp, they can offer me something expensive, regulated and with continuous voltage and current. On the one hand if I buy the variant at 3-5A, it does not behave well(short circuit protection come's up) at the spike I need. On the other hand if I buy the variant at 8-9A with 10A spike, it is more expensive, bigger and with some features that are not useful to me.

So, can some one come with a brilliant idea for what I need?

Thanks

Zero999:
I don't see what the problem is, your duty requirements are low so not much heat will be dissipated meaning you can derate the semiconductors accordingly. The only thing you can't derate is the magnetic cores since they'll still saturate.

What do you want, someone to do it for you? How much do you want to pay for someone to design it for you?

TechGuy:
Take a look at the LTC3721-1 Push-Pull Controller:
http://cds.linear.com/docs/Datasheet/37211fs.pdf

Last Page of the pdf has a 12V to 48V reference design for you. Although you will probably have to beef up the MOSFETS used and the transformer core used in the ref. design to handle a 10A burst @ 400ms. ~90% efficiency rating.

I would also recommend doing a google search for "Push Pull Controller" to see if these are other options that suite your needs.

For a Transformer core. I would go with either a P-core, PQ, or RM ferrite core to keep the PCB real-estate small. Toriods usually need a lot of board space and P,PQ,RM cores are much more easier to wind yourself. I doubt you will find a manufacture that provides an off the shelf 12-48V push pull transformer. For a production you can provide specs to a transformer winder vendor to run you a set of a few hundred custom transformers that meet your needs.


--- Quote ---The only thing you can't derate is the magnetic cores since they'll still saturate.
--- End quote ---

Increasing the switch speed can solve the saturation issue. Although you have to make sure the core material will operate at the higher switching speed. You can also increase the gap size in the transformer to extend the saturation point. But this lowers the inductance value and may need a higher switching speed to avoid excessive output noise and voltage drop under high load conditions.


Psi:
As promised, in case anyone was interested, here is the circuit diagram for that 10-15V input 12V output @ 10A psu i built ages ago.

I'm not 100% sure the values listed are what i ended up using.
And i built it 10 years or so ago, so it's probably not the best design. but hey, it worked, and was around 85% at 10A
It would be quite easy to add more turns on the secondary and get 24 or 48 volts output.


shabaz:
Funnily enough, I recently built a circuit to convert 12V to 48V to provide a constant 3A but the design can be modified for 5A constant. The link is here:
http://badcafe.co.uk/2011/03/17/48v-150w-power-supply-12v-step-up/

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