Electronics > Projects, Designs, and Technical Stuff
Is here way to increase efficiency of wide input boost over 95% ?
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T3sl4co1l:
At which point does increasing the cost of the converter reduce overall economy?  That is, will the 5W saved by pushing to 97% be worth the 500 cm^2 of panel area saved?

Are there other methods to improve efficiency or economy (better panel cooling? better optimized mechanical mounts, wiring, routing, fusing, busing?), and what is their relationship in the same tradeoff?

Likewise for NRE, is the design time worth it, amortized over product life?

Come to think of it, at current prices, going to 97 or 98% is probably quite justified.  99% or more, you'll be hard pressed to approach, expected design cost going up hyperbolically...

As for techniques, you may find it's worth using a lower frequency, to keep switching and core losses down.  You can afford to use rather large capacitors and inductors here.  Quasi-resonant commutation may be helpful, but don't expect good yields on switching energy (like, maybe you can reduce switching loss by 50%, 80% even, but eventually you will be limited by the high frequency losses of the snubber components, which have to operate at high rates of change).

Tim
Miyuki:
You are right with inductors, it can be much optimized with those ones.
And also budget wise it have no reason as panel cost is so low it wont make any reason to increase converter price (as panels itself is now about 0.3-0.4 $/Wp)

I think Ill go to 2 phase at 250kHz with
BSC500N20 transistor should have about 1.3W cond + 0.7W switch losses and is cheap
Cheap Ferrocore inductor two in series 15uH; 6A; 22mΩ - simmilar to Coilcraft MSS but cost just 0.4 $

All controlled with SAMD11

It seems to me as reasonable compromise between efficiency, BOM cost and time to put together
trobbins:
Will you be posting your breadboard results?  It would be good to see how close you got with your efficiency estimate, especially as you are operating at 250kHz.
Miyuki:
I am also curious how it will behave and how many times it will just release magic smoke violently to my face  :-/O
Hope Ill have a layout during this week
Siwastaja:
Do these "Cheap Ferrocore inductors" have core loss models / web software available?

AC loss can sometimes surprise you, even with ferrite-cored inductors. If you make an assumption of it being zero (or some percentage of DCR loss), you may succeed by luck, or not. Selection software like Wurth's Redexpert I like to use compare the total losses of parts, and you can sometimes see a certain part has 90% DC loss, 10% AC loss while some other part has the opposite! Total is, of course, the only thing that matters.

This being said, cheap, widely available inductors with no AC loss specifications are often worth of testing in prototyping. If you run them at rated DC current (with specified 40degC temp rise, for example), and notice that the actual temperature isn't that much more (i.e., measure 50 degC temp rise in your switcher), you can quickly see you were lucky regarding the AC loss.

I like to use "generic" SMD inductor footprints which have large pads so I can fit many sizes and types of inductors. And pick a footprint one size up from the inductor I think I will be using.
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