Electronics > Projects, Designs, and Technical Stuff
High efficiency DIY buck converter
drummerdimitri:
I'd like to build a buck converter to step down the 9-12.6V of a lithium ion pack to a constant 5V and 8A max as the adjustable one I bought from Aliexpress is terribly inefficient and generates too much wasted heat.
Is there a simple circuit diagram that achieves above 80% eff. and is capable of delivering the required power or is that too much to ask?
NiHaoMike:
Look for one based on a controller with synchronous rectification and low quiescent current. One I have used is the LTC1775, can do over 95% efficiency and not too difficult to build a complete regulator based on it from scratch.
ogden:
Quick search revealed "DC-DC Buck 9-35V to 5V 5AStep Down Synchronous Rectification Power Supply Module" that may meet efficiency numbers, yet may not be powerful enough. In case it is one-off project, then you may consider "branded" DC-DC module such as Meanwell SKA60A-05 (Input 9-18Vdc; Output 5Vdc at 12A).
SiliconWizard:
Define inefficient.
For this kind of ready-made modules, 80% would be about what to expect, and could hardly be qualified inefficient. Finding something as cheap (which I suppose it is) with better efficiency may take a while.
Designing it yourself - yeah, doing better than 80% if you have no preliminary experience with that, good luck!
Now if your module has significantly worse than 80% efficiency (are you sure? how did you measure it?), you probably either got ripped off, or you're not using it properly.
Lastly, just in case you haven't really measured the efficiency, but are basing your impression on the fact that the converter gets "hot": well, if it has say 80% efficiency in your conditions, it's still 20% loss. For the worst case, going from 12.6 to 5V @8A, that's a dissipation of 12.16W. Certainly enough to get a small converter very hot if it's not properly heatsinked.
mariush:
There's ready made dc-dc converter power supplies, here's some prefilter (anything 7.5A or higher, but make sure 5v is within its output range) : https://www.digikey.com/short/pfnq27
Basically you only need to add a couple capacitors and a resistor to set the output voltage if it's not fixed.
Datasheets contain the instructions on what's needed
There's also these dc-dc power supplies: https://www.digikey.com/short/pfnqn0
There's modules like this one.. expensive though: LTM4626 https://www.analog.com/media/en/technical-documentation/data-sheets/LTM4626.pdf
Something cheaper ( look up examples in datasheet)
UP to 96% efficient: https://www.digikey.com/product-detail/en/vishay-siliconix/SIC437DED-T1-GE3/SIC437DED-T1-GE3CT-ND/10244417
MPQ8634BGLE-P https://www.digikey.com/product-detail/en/monolithic-power-systems-inc/MPQ8634BGLE-P/1589-2005-1-ND/9817899
AOZ2264 https://www.digikey.com/product-detail/en/alpha-omega-semiconductor-inc/AOZ2264QI-18/785-1898-1-ND/10258107
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