Pico DC/DC 12V to ATX:: 160Watt at 15/30 euro?!? - Page 1
Forum section: electronics / projects

author: 0db
author_rank: Frequent Contributor
timestamp: May 27, 2020, 11:23:38 pm
content: Ordered a couple from two random guys on eBay- 80Watt, 30 euro + S/H-160Watt, 15 euro + S/H12V input, ATX voltages output.I am waiting for the parcels to be delivered, but you can guess the main question in my mind.Will it blow up?isn't 160 watt "a bit" unreasonable for such a DC/DC converter?especially considering the low price?What do think? I need a couple of such devices in the range of 60 Watt total.

author: Nominal Animal
author_rank: Super Contributor
timestamp: May 28, 2020, 02:58:15 am
content: picoPSUhave been around for well over a decade, typically used with mini-ITX form-factor PCs.Yes, they are that small. Seeherefor the review and testing silentpcreview did on them in 2006; reputable recently manufactured picoPSUs should be even better.No, 160W is not unreasonable, as it is essentially just a pair of DC-DC converters: one for 3.3V, the other for 5V, at max 8A current each. (Proper models should also have -12V and 5V standby, but their current limits are much smaller.) The OnLogic one I linked to can supply 8A @ 3.3V, 8A @ 5V, 8A @ 12V, 0.05A @ -12V, and 1.5A at 5V standby, at the same time.(Note that this does mean you should not expect more than 26W from the 3.3V line, 40W from the 5V line, or 96W from the 12V line; but you should be able to draw those from the three lines concurrently, if your 12V power brick can deliver at least 170W or so. Each line is effectively a separate DC-DC converter, except the 12V is likely straight through.)Expected retail price for the picoPSU-160-XT would be around 50 €. The price seems to have remained stable for all these years.Are the Chinese copies sold for under 20€ on Ebay and elsewhere reliable? I don't know, and it really depends on the quality of the parts used. It is a relatively simple design, having been around for years, so the question is how cheaply one can obtain the needed parts. It is quite possible they work just fine, I just don't know for sure.I wish I could give you a better answer, but I'm just a hobbyist with more experience with the computers that have used picoPSUs than electronics, so I'm the wrong person to say anything about the electronics of your particular purchases.

author: 0db
author_rank: Frequent Contributor
timestamp: May 28, 2020, 11:42:47 am
content: Quote from: Nominal Animal on May 28, 2020, 02:58:15 amMe too, I am just an hobbyst. Thank you for the answer =)

author: 0db
author_rank: Frequent Contributor
timestamp: May 29, 2020, 09:59:57 am
content: is there any trusted vendor or shop in Europe to buy a Pico DC/DC ATX PSU?

author: Nominal Animal
author_rank: Super Contributor
timestamp: May 29, 2020, 05:51:58 pm
content: These are established tech, so I would trust any model sold widely in Europe – the regulations being much tighter than for China exportsI myself could use a cheap one that is widely used in China; it's only the risk of getting a crap one off eBay/Banggood/others that I'd like to avoid.(As an example, the cheap USB (12 Mbit/s) isolators based on ADuM4160/3160 are absolutely fine, and work just as well as "official" ones, because they are straight off the ADuM datasheet. The only component to check is the isolated DC-DC 5V-5V converter on it, to check it isn't too noisy, and how much current it can provide from upstream 500mA at 5V. If your USB gadget needs less than 250mA or so, it's not a problem. The Olimex one has a power supply connector for device power, that is isolated from the computer ground, and is therefore a good buy for power-hungry USB devices. But the cheap Chinese isolators work for normal USB gadgets absolutely fine – and is something I'd suggest using if one connects e.g. their 3D printer to their computer via USB.)Here's some examples, no affiliation:CarTFT.comin Germany. They also sell bundles with known-good power bricks for 240VAC mains.Mini-ITX.comin UK.Mini-Box.comoffices are in the USA, but they have a sales office all over, including in South Africa (included just because your location flag is Zambia)I forgot to mention that they are very common in automotive uses (car computers); the -WI or Wide Input models are common there, because they can typically run off the battery voltage (which isn't nowhere near a stable 12 V).Since it is just a set of DC-DC converters, I would not call the copies "counterfeits" either. So, if you get a cheap copy, it is quite possible it works just fine. The way I'd check is to first check the parts. Then, if you have an electronic load, I'd test the 3.3V and 5V rails at up to 8A (separately) for fifteen minutes or longer, to see if the board gets hot, or there is too much noise on the rails.I've used the TI Webench to get examples of high-efficiency 5V-to-3.3V DC-DC converters, and I just now checked the 12V-to-3.3V suggestions. The LM25117 and LM5117 designs have a BOM cost of $12.71, require a board size of 1374mm2(say, 60mm × 22mm), and are 96% efficient above 4A (88% at 1A). (At 8A each at a conservative 92% efficiency the 3.3V and 5V converters produce 2.3W and 3.5W of heat, respectively. At 96%, just 1.1W and 1.7W; less than three watts of heat at full tilt.) So, there isnothingsurprising in PicoPSUs, and one could probably design an equivalent oneself – except that the "official" ones have been used for well over a decade, and have had the benefit of practical testing and real-world fixes and enhancements.

author: 0db
author_rank: Frequent Contributor
timestamp: May 30, 2020, 10:59:38 am
content: Thank you a lot! I am going to order a couple of modules for my colleagues, therefore we will have other modules to test. These two in the list look perfect.One of final applications of my colleagues is putting a mini computer on their boat to analyze the acquired data. They are biologists, and their computers need to be powered by the boat's battery.They need to plug in a dedicated PCIe card for the data acquisition and process, I know there are laptops with PCIe expansion, but they are much much more expensive, while a simple picoATX motherboard with a picoATX PSU can cheaply solve the problem. But the PSU must be the stablest possible, even under load, there is a kind of small GPU on their acquisition card, and avoid to dirty the acquired data dirty.Thanks a lot

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 30, 2020, 04:15:50 pm
content: A good quality ATX PSU connected to a 170/340V DC source would probably be the easiest way to get a galvanically isolated supply. That high voltage DC source can be a cheap (but reasonably good quality) inverter modified to tap off the internal DC bus. Add more filters between the DC source and PSU for further noise isolation.

author: ejeffrey
author_rank: Super Contributor
timestamp: May 30, 2020, 05:42:06 pm
content: Quote from: 0db on May 27, 2020, 11:23:38 pmRemember it's only 60-80 watts with a 12V passthrough.

author: Mr. Scram
author_rank: Super Contributor
timestamp: May 30, 2020, 05:46:54 pm
content: As people have noted correctly but I want to emphasize the quality of your 12V brick is important. The 12V line is essentially passed through directly and both your efficiency and ripple and noise depend on the quality of the brick. While a wider input version is also sold the fixed 12V versions seem to be more efficient. I wouldn't really bother with fakes as the original isn't hugely expensive and well proven.

author: bingo600
author_rank: Super Contributor
timestamp: May 31, 2020, 07:16:15 am
content: I'd suggest to order the "Red" HV version (High voltage) , if possible. Then you can use up to 25v input.Cheap laptop chargers are excellent candidates for the HV version./Bingo

author: Mr. Scram
author_rank: Super Contributor
timestamp: May 31, 2020, 07:30:57 am
content: Quote from: bingo600 on May 31, 2020, 07:16:15 amThose are the wider input versions I spoke of and those are the ones you don't want. The combination is less efficient than just using the correct brick.

author: mikerj
author_rank: Super Contributor
timestamp: May 31, 2020, 09:36:13 am
content: Quote from: Mr. Scram on May 31, 2020, 07:30:57 amLikely to give a better regulated 12v line though.

author: 0db
author_rank: Frequent Contributor
timestamp: May 31, 2020, 02:58:56 pm
content: The input power is the 12V battery used on the boat.

author: mariush
author_rank: Super Contributor
timestamp: May 31, 2020, 05:05:01 pm
content: The 12v on a boat may not be "clean", I suppose it could be up to 13.8v or whatever is the charging voltage.A HV (wide input range) picoPSU will regulate the 12v as well, but the output current on 12v will be fairly small, something like 10-20A or around 100wYou'd probably be better off buying an inverter to convert 12v to AC and then use a regular gold/platinum efficiency psu ... you lose some energy through the conversion from 12v to AC but you can probably top up the battery (maybe also use some solar panels throughout the day)

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 31, 2020, 06:09:19 pm
content: Quote from: mariush on May 31, 2020, 05:05:01 pmSkip the converting to AC part of the inverter (using only the DC step up part) to help reduce noise. Very easy mod - just identify the high voltage DC output from the rectifier and tap into it.

author: 0db
author_rank: Frequent Contributor
timestamp: May 31, 2020, 06:48:55 pm
content: Quote from: mariush on May 31, 2020, 05:05:01 pmAh, ok. The 12V rail on the computer-side only needs 6A. It should be enough.

author: wizard69
author_rank: Super Contributor
timestamp: May 31, 2020, 09:10:24 pm
content: Quote from: 0db on May 31, 2020, 02:58:56 pmIf that is the case get a power supply specifically designed for use on automotive 12 VDC supplies. The reason is you can't pass the 12VDC through to sensitive electronics As has already been mentioned charging voltage are usually just under 14 volts which may be a problem on many motherboards. It actually can be a lot worse than 14 VDC due to power dumps, transients and so forth, that are common on cars or in this case boats. To put it another way the automotive DC system is not clean DC power. The age of the boat and its motor, plus the quality of the electronics used in it can also be factor.

author: Nominal Animal
author_rank: Super Contributor
timestamp: June 01, 2020, 05:26:54 am
content: Quote from: wizard69 on May 31, 2020, 09:10:24 pmAw carp, I forgot about automotive environments. (Never dealt with those myself, always have nice clean power bricks myself.)TheM3-ATXat CarTFT and elsewhere looks like a good candidate, although it's only 125W: 6A @ 3.3V, 6A @ 5V, maximum current at 12V depending on the battery voltage but for 11-16V, 6A @ 12V; all peak 8A for less than 30 seconds, with regulation to 1.5%. These have battery protection circuits (turn-off if battery voltage drops too low), transient suppression, and are supposed to deal with hard engine cranks (sagging voltage) etc. This particular model is PicoPSU-size, too.I'd say the PicoPSUs are good if you run them off a power brick or their own regulated 12V battery pack (a 12V UPS like things, with internal DC-DC conversion to a stable 12V).If the power comes directly from a 12V nominal battery, or the supply has other devices on it, especially if any kind of motor on it like a starter motor, the M3-ATX and similar are a much better choice obviously.

author: 0db
author_rank: Frequent Contributor
timestamp: June 01, 2020, 08:59:00 am
content: Quote from: Nominal Animal on June 01, 2020, 05:26:54 amOn boat, there is a DC/DC regulator probably with some extra filtering on the cabin where the 12V is used for the navigation system. and for the radio.Yesterday I measured 11.9V with 80mV of ripple with the motor off. And 12.2V with 120mV with the motor on.

author: Nominal Animal
author_rank: Super Contributor
timestamp: June 01, 2020, 10:15:27 am
content: Quote from: 0db on June 01, 2020, 08:59:00 amThat's what I suspected.Quote from: 0db on June 01, 2020, 08:59:00 amThe originalATXpower supply specs require the +12V line to be between 11.4V and 12.6V, with max. 120mV ripple, and I think but am not sure that still applies to current ATX power supplies. In any case, I suggest you check the motherboard/PCIe card specs for their requirements.

author: Nominal Animal
author_rank: Super Contributor
timestamp: June 01, 2020, 10:35:48 am
content: Note that theM2-ATXcan provide 8A at 3.3V, 8A at 5V, and 8A at 12V, from 10V to 26V (it's an automotive PSU), with 1.5% regulation on 3.3V and 5V and 2.0% regulation on 12V. It has a different form factor (you use an ATX-ATX jumper cable between it an the motherboard), having a 160mm × 45mm board, but depending on the computer enclosure, can be easier to mount in a place it gets some airflow.(120mV of ripple at 12V, assuming you meant peak-to-peak, is only about 1%, so I amnotsaying you need an M2-ATX instead of a PicoPSU at all; the 120mV ripple on the 12V line is something a generic ATX power supply can have, and still be within the spec. But, if you do intend to draw 6A from the 12V line, it might be prudent to ensure good airflow, and it is easier for this form factor than PicoPSU form factor, unless you have plastic baffles to direct airflow. Just wanting you to know of the alternatives here.)The reason I used links to CarTFT.com is because it is in Europe and has manuals and/or datasheets with detailed information (current limits, ripple, etc.) in the Data sheets and downloads tab. But lots more shops sell these.