70v to 12v step down converter - Page 1
Forum section: electronics / projects

author: ambrozy
author_rank: Contributor
timestamp: November 26, 2022, 11:38:28 pm
content: I have quite annoing problem, I need 12v at <100ma from 16s li-ion pack, so up to ~70v, all converters I can find works up to 40vin max and all "AC" converters usually starts at ~80v, what would be the solution here without designing and making such converter by myself?

author: georges80
author_rank: Frequent Contributor
timestamp: November 26, 2022, 11:44:40 pm
content: Searching Digikey brings up plenty of options, nothing down at only 100mA, but certainly quite some choice at 1A output.I'm assuming Mouser has a decent selection too. As likely do other distributors.cheers,george.

author: Swainster
author_rank: Frequent Contributor
timestamp: November 27, 2022, 12:27:26 am
content: As George says, the search function of digikey or its competitors should bring up plenty of hits. I'd like to add that this is a common specification for railway DC/DC converters, so you could add that to your search terms to see what pops up.

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 27, 2022, 10:25:28 am
content: https://www.eevblog.com/forum/projects/100v-vin-buck-regulator-options/msg4545938/#msg4545938whats odd is the Vout < Vin - 5V spec, but $1-2 try wont hurt imho...

author: Psi
author_rank: Super Contributor
timestamp: November 27, 2022, 10:57:15 am
content: Or you can throw a $2.80 at the problem and get complete DCDC module that's all ready to go.Non-Isolated PoL Module DC DC Converter 1 Output 12V 500mA 18V - 90V Input 91% Efficient.https://www.digikey.com/en/products/detail/mornsun-america-llc/K78U12-500R3/16571412All you need is a couple of ceramic caps.

author: Terry Bites
author_rank: Super Contributor
timestamp: November 27, 2022, 05:36:52 pm
content: The LM5017 is right up your street. See attched 12V 0.6A design genrated by webench.ti.com/power-designer/

author: mariush
author_rank: Super Contributor
timestamp: November 27, 2022, 08:08:10 pm
content: SM72485SDE 95v in max, 150mA max output, :https://www.digikey.com/en/products/detail/texas-instruments/SM72485SDE-NOPB/2682791BD9G341AEFJ 76v in max, 1A max output current, more expensive :https://www.digikey.com/en/products/detail/rohm-semiconductor/BD9G341AEFJ-LBE2/7896419

author: Psi
author_rank: Super Contributor
timestamp: November 28, 2022, 06:23:25 am
content: Really no point rolling your own from an IC unless you can make it much cheaper than $2.80 for a finished DCDC brick.

author: mariush
author_rank: Super Contributor
timestamp: November 28, 2022, 04:34:51 pm
content: It could be height constrained ... thing's kind of big at 17.5mm x 11.5mm x 9mm ... or there could be other reasons why that specific product would not work.

author: Zero999
author_rank: Super Contributor
timestamp: November 28, 2022, 06:16:02 pm
content: Is this a one off, hobby project or is it mass produced? If it's just a one off, try a universal mains power supply. Many of them will work down to 50VDC, or so. Bear in mind the current through the rectifier and internal switching transistor will be higher, so it's a good idea to de-rate it.

author: ambrozy
author_rank: Contributor
timestamp: December 02, 2022, 12:43:53 am
content: It is a one off hobby project, I don't have any universal mains power supply that goes that goes lower than 80v, I've found AMSRW-7812-NZ, it's not cheap for such thing but I need just one, other similar power supplies are ridicolously expensive like 40usd+ and most of them not even in stock in my country, maybe that AMSRW-7812-NZ will do for now.