I need to get an even 19V out from a 4S LiPo input, which ranges from 16.8V when freshly charged, to 12.8V when fully discharged. I need between 0.7A and 1.5A out. (This is driving a small computer – a Zotac Zbox nano AD11)
Item 799 ( pololu.com/catalog/product/799 ) says that it can generate up to 24V, and that the input voltage is up to 16V.
Does this mean it won’t work at 16.8V (such as exceeding the allowable voltage for a MOSFET switch or whatever,) or would this application actually work?
I do not think it would be good, both for the 16V max input reason and also because your current is kind of high. At 1.5A out and 80% efficiency, the input voltage would have to be 17.8V to stay under the 2A input limit. The 24V efficiency graph shows a 9V input cutting out under 400 mA and 12V cutting out under 500 mA, so I think that even if the efficiency is closer to 90%, the total power is high enough that the 10-15% of inefficiency will cause overtemperature issues before you get to 1A out.
You’re right. That’s a shame!
I have an MC34063 around here, and while it’s normally not a very efficient circuit, if I couple it with a IR2301 and a N-channel MOSFET, I can probably build my own boost converter. (And a big inductor and capacitor set.) A lot bigger and clunkier than your nice circuit, though