30V/5A SMPS IC tips/ideas? - Page 1
Forum section: electronics / projects

author: justanothercanuck
author_rank: Frequent Contributor
timestamp: January 18, 2015, 01:09:56 am
content: So a while back, I was debating on whether I wanted to buy a bench supply or build one myself. I didn't like the prices for my local offerings, so I was considering making a supply myself using something like the LT3080/3083, that was until the whole thing about the regulator being a bad design or something. At any rate, I got busy, had to move, and it got put on the backburner with all my other projects.Anyways, I wanted to dig up the bench supply idea again, and thought about going the SMPS route. I'm still looking to have the supply operate at 0-30V/0-5A, so I'll need something I can parallel up in buck or buck-boost mode. I had a look at Maxim, TI and OnSemi, but sadly I'm still lost. Some of these IC's have all sorts of features that I probably don't need (ULVO, soft start, on/off control, auto restart), or their voltage or current output are too low for my design intentions.Anyone got tips for choosing a SMPS IC? Thanks(Yes I know I should probably just buy a bench supply at this point, but I don't have any decent local stores, and shipping can be expensive, even in Canada, especially if it's imported from the US and I have to pay duty... ugh I hate shipping.)edit: doesn't help when sites like Mouser list an IC as having 3A output, to read the data sheet and find out it's only good for 100mA. TL5001, I'm looking at you...edit: actually, I think I may have figured it out... I can use the LM2678 to get to 30V if I use a voltage divider on the feedback pin and group the outputs together between the LC circuit and the feedback resistors.

author: justanothercanuck
author_rank: Frequent Contributor
timestamp: January 18, 2015, 02:54:45 am
content: I was going to buy a 120V to 48V/250W transformer, and do full wave rectification. Should be enough headroom to run the IC's at the full 30V output, and even if it's not, I probably won't need the full 30V enough for it to matter.On the other hand, I'm looking at part prices... the IC's are $7 a piece (x2 if I want 5A without running them at full blast), a transformer is like $115 (let alone the shipping for something that almost weighs 10lbs - edit: $46 shipping?? Get out of here...) Starts getting into the pricey territory, but I would have had to buy the transformer either way I suppose.

author: void_error
author_rank: Frequent Contributor
timestamp: January 18, 2015, 07:19:50 am
content: Quote from: justanothercanuck on January 18, 2015, 02:54:45 am36V/250VA is probably enough, you'll get about 50V after rectification/filtering at no load assuming a 120V input. If you're running the whole thing without a switchmode pre-regulator expect to spend some $$$ on a beefy heatsink and a truckload of output transistors...

author: peter.mitchell
author_rank: Super Contributor
timestamp: January 18, 2015, 07:30:55 am
content: I know building one seems like a lot of fun and all and you *could* save some money, but really i'd just get one oftheseand be done with it.

author: justanothercanuck
author_rank: Frequent Contributor
timestamp: January 18, 2015, 03:21:30 pm
content: Quote from: peter.mitchell on January 18, 2015, 07:30:55 amYeah, I know.Why are the output posts on the back?

author: void_error
author_rank: Frequent Contributor
timestamp: January 18, 2015, 11:27:33 pm
content: Quote from: justanothercanuck on January 18, 2015, 03:21:30 pmSo they could fit their big fat logo

author: justanothercanuck
author_rank: Frequent Contributor
timestamp: January 19, 2015, 05:11:23 am
content: This might fit the bill for me...http://www.ebay.ca/itm/ZXY6010S-DC-Constant-Voltage-Current-Power-Supply-Module-60V-10A-600W-w-TTL-/111020252080http://www.mhinstek.com/product/html/?98.htmlFor all I know, it's a piece of crap, but it's only ~$100 and all I would need is a reasonably-sized wall-wart to power it.I was looking at their B3008, but apparently.

author: Christopher
author_rank: Frequent Contributor
timestamp: January 19, 2015, 06:28:19 am
content: Instead of an iron core transformer, how about a high quality laptop charger? Most of these are 19 at various output powers.A buck boost with digital pot feedback would be a great addition

author: void_error
author_rank: Frequent Contributor
timestamp: January 19, 2015, 07:59:28 am
content: Quote from: Christopher on January 19, 2015, 06:28:19 amLaptop chargers usually output less than 100W, unless it's a gaming laptop, but those don't really go above 150W.