high power +30v  psu - Page 1
Forum section: electronics / projects

author: p.larner
author_rank: Frequent Contributor
timestamp: September 28, 2023, 06:13:07 am
content: has anyone got any plans for say a 0-20amp 0-60 ish volt diy psu with cc+cv,i have a huge transfo about 30cm square with a 47v tap,+some big diodes and caps etc,opamp or 723 based.?

author: jonpaul
author_rank: Super Contributor
timestamp: September 28, 2023, 06:17:16 am
content: Wrong title...THIS IS NOT HIGH VOLTAGEHigh voltage = > 600..1 kV.Mains = 120/240j

author: p.larner
author_rank: Frequent Contributor
timestamp: September 28, 2023, 06:38:43 am
content: well over the normal 30volts!

author: Psi
author_rank: Super Contributor
timestamp: September 28, 2023, 07:02:41 am
content: I don't consider it high voltage until you can get it to arc between wires

author: Zero999
author_rank: Super Contributor
timestamp: September 28, 2023, 07:27:43 am
content: Quote from: p.larner on September 28, 2023, 06:38:43 amNo. It's extra low voltage, which is defined as under 120VDC or 50VAC, but it still requires basic insulation, although no earth. In dry areas, voltages under 60VDC or 25AC don't need to be insulated. In damp areas, where there's a high risk of shock, all live conductors need to be insulated.Quote from: p.larner on September 28, 2023, 06:13:07 amIn another thread you mentioned you have a restricted budget, which makes this impractical, as it will be expensive.Presumably you're talking about a linear, rather than switched mode supply? It would require a custom transformer, with many taps to keep power dissipation to a minimum.

author: jonpaul
author_rank: Super Contributor
timestamp: September 28, 2023, 07:40:42 am
content: Defs:https://en.wikipedia.org/wiki/Extra-low_voltageIEC voltage range AC RMS voltage (V) DC voltage (V) Defining riskHigh voltage > 1,000 > 1,500 Electrical arcingLow voltage 50 to 1,000 120 to 1,500 Electrical shockExtra-low voltage < 50 < 120 Low riskSELV: UL Safety Extra low Voltage 42.2 V peak OR less;Here is a great REALLY high volktage site.....https://lod.org/(Lighting on Demand, our old friend Greg LEYH)Enjoy,Jon

author: PCB.Wiz
author_rank: Super Contributor
timestamp: September 28, 2023, 08:40:24 pm
content: Quote from: p.larner on September 28, 2023, 06:13:07 amThat's high voltage for semiconductors ICs and they have thinned out for linear up there.Parts like TL783 manage 125V, but they are the LM317 family with a 1.25V drop, so the ADJ pin needs to be driven to Vo-1.25, needing a high voltage opamp.A TPS7A4001 is good to 100V and 50mA, so might work with a darlington output ?Or, you could just choose a HV opamp like OPA455, OPA462 ? and simple darlington follower.You will need a massive heatsink array of big output devices to manage 60V 20A peaks, that's 1200W !Or, you could use the driver level shifting seen in Audio Power amps, to allow lower voltage opamps

author: Benta
author_rank: Super Contributor
timestamp: September 28, 2023, 09:08:47 pm
content: I look forward to seeing your cooling approach. Dissipating >1.2 kW worst case takes some doing.

author: moffy
author_rank: Super Contributor
timestamp: September 28, 2023, 10:19:56 pm
content: Quote from: Benta on September 28, 2023, 09:08:47 pmBenta is correct, a better approach is maybe a multitap transformer with tap switching or perhaps a switch mode pre regulator followed by a linear post regulator or just switch mode.

author: John B
author_rank: Frequent Contributor
timestamp: September 28, 2023, 10:25:07 pm
content: What application are you needing a linear supply with 20 amps?

author: TimFox
author_rank: Super Contributor
timestamp: September 28, 2023, 10:51:14 pm
content: Following Benta's post:If you really want to run this level of power in a linear supply, you should start the design process from the heat-sink/cooling end, then work backwards to the control circuit, etc.

author: p.larner
author_rank: Frequent Contributor
timestamp: September 29, 2023, 12:50:48 am
content: forgot to say the transfo has taps at the following voltages 1.5v 2v 2.6v 3.5v 6.2v 21v 26v 38v :i build ebike batterys so would be handy for charging those,also just would be a handy thing to have.,thought of using a chinese 0-30v 5a psu pcb kit as they are opamp based and have tap switching.maybe just change the current sense resistor?.

author: moffy
author_rank: Super Contributor
timestamp: September 29, 2023, 01:28:23 am
content: Quote from: p.larner on September 29, 2023, 12:50:48 amIf it's primarily for charging purposes then PWM/switchmode is the most economical way to go.

author: coromonadalix
author_rank: Super Contributor
timestamp: September 29, 2023, 01:36:36 am
content: you can base this circuit and evolve it ... from astron 50 50 amp psu ....youcan make it variable down to 1.2volts and add an variable current etc ...or this one tooPyramid PS52KXsame mods can be done on this one too

author: PCB.Wiz
author_rank: Super Contributor
timestamp: September 29, 2023, 01:40:11 am
content: Quote from: p.larner on September 29, 2023, 12:50:48 amYou are better to pick one rated to more current, if you want to use all the ability of the transformer.Ones like this claim 60V 20A - but are switching. If you just want to charge batteries, it should be fine ?https://www.aliexpress.com/item/1005005558425514.htmlor this claims 25A, looks to have better tunnel cooling.https://www.aliexpress.com/item/1005005639051641.htmlthis one claims 50Ahttps://www.aliexpress.com/item/1005005884099336.html

author: p.larner
author_rank: Frequent Contributor
timestamp: September 29, 2023, 03:01:15 am
content: i dont realy need one badly,its just i have this monster transformer that i payed a fiver for at a hamfest sitting on my floor and thought it was time i got round to building something usefull with it couldnt pass on it for five pounds,orth more than that for scrap copper i would think.

author: mawyatt
author_rank: Super Contributor
timestamp: September 29, 2023, 01:39:13 pm
content: We needed 60 to 90V at 15 amps peak, so just ordered a Korad KWR103 (60V at 15 amps) to go with our KWR102 (30V at 30 amps). The KWR103 is only 60 volts tho, so for higher output voltage we'll need to stack them and see how this works. This is for receptive pulsed applications, not continuous load.Best,