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dc-dc Buck vs boost efficiency Answered

Hi guys.

When you  use solar panels and have gadgets with different voltage requirements  that you want to power up.

I need atleast  2 different outputs, 5v and 12v  ,  

so which is most efficient ,  12/15v panels that you  regulate to 5v , or  5v panels boosted  to 12v?

is there any general advantage in either case

and i,m talking about using  cheap ebay switch regulators / boost converters,  not anything expensive hi tech.



In general buck supplies are more efficient than boost, but Ebay crap isn't likely to push the envelope, because they'll use cheap parts, and particularly the inductors will be badly made.

Ok,that suprised me, i always have thought the opposite

prob cause i tend to think regulating downwards always has to dissipate power into heat

....and regulating upwards gets the energy from where...

No, the higher available voltage improves switching in the power devices, and reduces the switch current

Trying to boost a 5V panel to 12V may be an issue since you sacrifice amperage for voltage. If the panel can't supply enough amperage then you won't be able to boost it to 12V. So start with a 12V panel and regulate it down to 5V. You can use a decent switching regulator rather than your typical 7805 so you don't loose as much efficiency.

It would be best if you use the panel to charge a battery then run your regulator or boost off the battery to your devices.