| Electronics > Projects, Designs, and Technical Stuff |
| Pico DC/DC 12V to ATX:: 160Watt at 15/30 euro?!? |
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| 0db:
Ordered a couple from two random guys on eBay - 80Watt, 30 euro + S/H - 160Watt, 15 euro + S/H 12V 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? :D 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. |
| Nominal Animal:
picoPSU have been around for well over a decade, typically used with mini-ITX form-factor PCs. Yes, they are that small. See here for 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. |
| 0db:
--- Quote from: Nominal Animal on May 28, 2020, 02:58:15 am ---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 --- End quote --- Me too, I am just an hobbyst. Thank you for the answer =) |
| 0db:
is there any trusted vendor or shop in Europe to buy a Pico DC/DC ATX PSU? |
| Nominal Animal:
These are established tech, so I would trust any model sold widely in Europe – the regulations being much tighter than for China exports :) I 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.com in Germany. They also sell bundles with known-good power bricks for 240VAC mains. * Mini-ITX.com in UK. * Mini-Box.com offices 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 is nothing surprising 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. |
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