Comparison of DC-DC converters - Page 1
Forum section: electronics / general

author: confusion
author_rank: Contributor
timestamp: November 29, 2024, 05:38:38 am
content: Hi,I'm trying to power a few IoT items in an offgrid cabin. The house system is 12vdc1. DIY Victron Cerbo + Touchscreen running on a Raspi2. ESP32 running ESPHome3. Another ESP32 running a Bluetooh proxyThey all take micro USB.I could just give 5v strait to GPIO pins but I think I prefer the ease of use of micro cables.I'm looking at a few different DC-DC converters/regulators but don't really know how to assess their merits.Safety is #1 on top of the listEfficiency is also selling point as it's offgrid so the available power is preciousPrice isn't a concernAny help with identifying the types of units here and their differences would be much appreciated.#1https://www.aliexpress.com/item/1005007820239287.html?spm=a2g0o.cart.0.0.7ee538da0OW4qT&mp=1#2https://www.aliexpress.com/item/1005006296995025.html?spm=a2g0o.cart.0.0.7ee538da0OW4qT&mp=1#3https://www.aliexpress.com/item/1005007318164841.html?spm=a2g0o.cart.0.0.7ee538da0OW4qT&mp=1If these units are kinda dodgy I could always get something like a Meanwell DC-DC DIN rail mounted unit and make it work. They all seem to be 100-240vac inputs though and I'm running a 12V system in the cabinThanks heaps

author: Someone
author_rank: Super Contributor
timestamp: November 29, 2024, 07:04:45 am
content: Quote from: confusion on November 29, 2024, 05:38:38 amThen importing no-name or counterfeit junk is probably the wrong way to go."caravan USB socket"Plenty of local options in various feature sets.

author: confusion
author_rank: Contributor
timestamp: November 29, 2024, 03:28:13 pm
content: Quote from: Someone on November 29, 2024, 07:04:45 amThank you for your input. I would love for a recommendation or criticism of what I've listed. I'm trying to learn about the differences between the devices and figured this was the place to ask.As I understand it, the internals of a "caravan USB socket" would probably be the same as some of the items I've listed and I'd like to know more about them in order to make a better decision. Some of the devices have coils and some don't. I'm not sure what that means and would like to learn.

author: Babbsdrebbler
author_rank: Newbie
timestamp: November 29, 2024, 04:27:05 pm
content: #3 is wild.Is that a barrel jack to IEC-60320-C8 cable?And the missing polarity safety of that cable is then explained with “Rectifier Bridge. Do not distinguish between Positive and Negative.”I think you could plug the device into mains with a suitable cable but since it’s rated to 36V DC the magic smoke would exit immediately.

author: Someone
author_rank: Super Contributor
timestamp: November 29, 2024, 08:10:51 pm
content: Quote from: confusion on November 29, 2024, 03:28:13 pmYes, the internal may well be similar, but if you buy from a domestic (Australian) retailer then they are taking on the liability for safety, which generally just works and you end up with a safe product. You importing from mystery seller is you taking on the responsibility.Yes, you can save some money. But you're asking us to spend out time for free so you can save a little money.Electrical safety is not something you can learn in a few replies in a thread, it's an entire career.

author: confusion
author_rank: Contributor
timestamp: November 30, 2024, 12:35:42 am
content: Quote from: Babbsdrebbler on November 29, 2024, 04:27:05 pmYeah that seems like a really dumb design choice. If I were to use that one I'd cut the end off it, fuse and hardwire it.Quote from: Someone on November 29, 2024, 08:10:51 pmI was actually asking about inductors. In an electrical engineering forum. If you think that's a terrible waste of your time and instead of reaching out to those with knowledge I should instead make a career in the field. I don't really know what to say to that..

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 30, 2024, 12:43:28 am
content: Quote from: confusion on November 30, 2024, 12:35:42 amJust plug in the adapter and superglue it in place.

author: Someone
author_rank: Super Contributor
timestamp: November 30, 2024, 01:38:15 am
content: Quote from: confusion on November 30, 2024, 12:35:42 amPerhaps you can point out where you asked about inductors? What do you want to know about inductors? I see a bunch of links out to a well known junk market and asking for people to help you select a safe item.Quote from: confusion on November 29, 2024, 05:38:38 am

author: confusion
author_rank: Contributor
timestamp: November 30, 2024, 03:13:43 am
content: Quote from: Someone on November 29, 2024, 08:10:51 pmQuote from: confusion on November 29, 2024, 03:28:13 pmI find your attitude quite hostile and I'm not getting any value from exchanges with you. I would appreciate it if we just left it there

author: Andy Chee
author_rank: Super Contributor
timestamp: November 30, 2024, 05:57:39 am
content: Quote from: confusion on November 29, 2024, 03:28:13 pmI might be bold enough to state that all devices for your intended application have inductors/coils.So when you refer to devices without inductors/coils, to which device do you speak of?Answering this question may allow us to properly understand your concerns.

author: confusion
author_rank: Contributor
timestamp: November 30, 2024, 06:23:29 am
content: Quote from: Andy Chee on November 30, 2024, 05:57:39 amThanks for the reply mate,My concerns are I'm in the market to buy something I don't know the first thing about and wanted somebody else to weigh in. That's all.I don't know if some designs are inherently safer, more efficient or long lived.It's going to be installed and running on a permanent basis in an off grid property so I wanted to do some due diligence.When I was referring to devices without coils I was just making an observation that in the pictures one has a single visible coil, another has two and the the third unit doesn't have any visible. I'm sure you're right though and it's tucked away in one of the SMD packages.

author: Andy Chee
author_rank: Super Contributor
timestamp: November 30, 2024, 06:41:15 am
content: Quote from: confusion on November 30, 2024, 06:23:29 amSo when you talk about “design” you are referring to manufacturing research and development design and build quality?

author: confusion
author_rank: Contributor
timestamp: November 30, 2024, 06:59:23 am
content: Quote from: Andy Chee on November 30, 2024, 06:41:15 amNo, I was talking about the different architectures or types of step down converters.If you are willing or capable of looking at specs and a picture, then making comment, all the better.Cheers

author: Andy Chee
author_rank: Super Contributor
timestamp: November 30, 2024, 07:10:01 am
content: Quote from: confusion on November 30, 2024, 06:59:23 amOk if you are talking about comparing circuit topologies, then you will need to provide specific examples to which we can compare, contrast, and critique.Your provided Aliexpress links give no indication of circuit architecture.

author: confusion
author_rank: Contributor
timestamp: November 30, 2024, 07:39:23 am
content: That's a shame, I was rather hoping for some general advice but if you need specific details to make that kind of judgement call then I guess I'm still at square one. Thank you for your time.

author: Andy Chee
author_rank: Super Contributor
timestamp: December 01, 2024, 12:09:22 am
content: The general advice is that for the purposes of 12V DC to 5V DC conversion, there is only one circuit topology that is dominant; the non-isolated buck converter.Given that this inductor based topology dominates 99.99% of this market, the general advice for your intended use case is to stick with this topology.There are other circuit topologies in the remaining 0.01%, including inductor-less designs. However, the general advice is to ignore them.Incidentally, circuit topology is normally NOT specified in the product details, hence the unusual request for you to provide specific examples where you have come across them.

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 01, 2024, 03:37:20 am
content: Maybe what he's referring to is synchronous vs. standard buck converters. The synchronous converters should be better, but in practice, a lot of the modules are always CCM meaning their idle power use is pretty bad. (That includes some older ones from name brands like TI!)

author: Andy Chee
author_rank: Super Contributor
timestamp: December 01, 2024, 04:00:15 am
content: Well he also refers to safety being #1In the context of DC-DC converters, what does that mean? Over voltage protection? Short circuit protection? Electrocution hazard? Static protection? RFI protection?These issues aren't really topology related at all, and relate to the manufacturing R&D of the product, which according to post #13 is not what the OP is concerned about.

author: confusion
author_rank: Contributor
timestamp: December 01, 2024, 12:01:52 pm
content: It's really not any more complicated than I need to power a few 5v devices in perpetuity and I thought I'd reach out here for some advice on the hardware I should be looking at. I don't exactly feel comfortable with what I've found and would be more than happy to spend up to $100 to get something that fits the bill, I just don't know what that hardware is or who manufactures it.Should I be looking at potted 12v to 5v converters and making my own USB cables or running it strait to the pins?Am I being pedantic looking at the items off Ali and being apprehensive about using them?What would be industry best practice to power a few 5v devices totalling less than about 30wApologies if I haven't made my use case very clear.

author: Krotow
author_rank: Regular Contributor
timestamp: December 01, 2024, 12:40:12 pm
content: I see where this is goingHad to deal with customers who cobbled together random junk from Aliexpress even inside at street installed boxes. And then complained about instability and brownouts. If safety definitely is #1, get adequate power supply that certified to work within parameters you need.Funny power connector choice for Chinese electronic modules is usual thing. Those guys will put together anything that barely conduct electricity and will not instantly cause a short circuit. I have a 230V AC powered hot plate (Mechanic IX5 Ultra) with XT30 as mains cable connector at device side. Lovely thing that do the job just fine. But had to put big red labels on cable and device power connector to know that XT30 here is not used for low voltage DC.

author: confusion
author_rank: Contributor
timestamp: December 01, 2024, 02:20:02 pm
content: Might have found one I can use.I've given up on finding something with USB ports.SD-25A-5https://au.element14.com/mean-well/sd-25a-5/dc-dc-converter-5v-5a/dp/2816175

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 01, 2024, 02:43:58 pm
content: Quote from: confusion on December 01, 2024, 12:01:52 pmSomething like this?I suggest looking within RV communities, they'll be able to suggest some options that are reliable but still fairly cheap.

author: confusion
author_rank: Contributor
timestamp: December 01, 2024, 11:29:58 pm
content: I actually have one of those Pirl units from a Kickstarter many years ago I completely forgot about.Thanks a bunch for reminding me!