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1kW 200/400V dc/dc converter design tip
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Benta:
Which inductor have you chosen? This is a key question.
Amper:
Even though his is a different kind of inverter and the power is multiple times larger i like to see some mildly similar things for comparison:

coppercone2:
hmm, I am just curious. Would tantalum caps work, or maybe wet tantalums, to get size down while increasing reliability close to film caps? (if they are properly over rated). ?

like hermatic ones.
David Hess:

--- Quote from: coppercone2 on January 28, 2019, 01:24:52 am ---hmm, I am just curious. Would tantalum caps work, or maybe wet tantalums, to get size down while increasing reliability close to film caps? (if they are properly over rated). ?

like hermatic ones.
--- End quote ---

Tantalum parts could be used but would be awfully expensive and they are only available up to about 50 to 100 volts for hermetic packages.  You might find them in a military, aerospace, or extreme industrial application.  Polymer electrolytics would be better for lower ESR and higher ripple current rating but they are only available in even lower voltages.  That leaves aluminum electrolytics, film, and ceramic.
jbb:
Well, a SiC MOSFET + Schottky diode is almost certainly the right tool for this job. A Gallium Nitride (GaN) device might be a bit better. PCB layout will be absolutely critical to get the best performance out of your devices.

You could reduce the diode conduction losses by using a second MOSFET as a synchronous rectifier.

You mention using a ‘transistor’ instead. MOSFETs, IGBTs and BJTs are all types of transistor.

In terms of changing the switching frequency, you’ll have to look at the knock-on effects on inductor current ripple and therefore turn on and turn off currents. It would also change the point at which you go to discontinuous conduction mode.  If you want to go full nerd on it (and why not :)) with an optimiser I suggest you design for peak efficiency at 50% load but still check temperatures are OK at 100% load.

For improved efficiency at light load you could consider using a burst mode.
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