DC power supply - Page 1
Forum section: electronics / beginners

author: Napiza
author_rank: Newbie
timestamp: July 14, 2021, 04:18:06 pm
content: Hi to everyone!Thanks for giving attention to my message. I am starting to design a DC power supply and I have some questions when choosing the bridge rectifier. I have a center tapped transformer of 25-0-25 V and 4A.- Would it work the GBU 1001 rectifier?? I thing I've attached the datasheet correctly below. It has-How can I size the Heatsink to put into it? I suppose it depends on the load no? so I fisrt has to choose the regulators in terms of being accurate enough?-The last question is more related with theoretical doubts. When they give the voltage and the current on the secondary of the transformer, under which load conditions are given, in an open circuit?Thanks and sorry for my english, is not my language so I try to do my best!Nagore

author: SuzyC
author_rank: Frequent Contributor
timestamp: July 14, 2021, 05:39:12 pm
content: 1) The 1001 is good enough, you only have reverse voltages <80 V2) The datasheet clearly shows operation at 10-amps with a 1.5cm x 1.5 cm 1.6mm copper plate heatsink. Anything metal will work if larger, like the chassis you build it in. Use heatsink compound and don't overtorque the mounting screw/nut. A heatsink needs some ventilation if mounted on the rectifier in free air. Heat can build up in a closed box, maybe you will need some vent holes in a chassis box.3) The transformer voltage is the voltage at rated current.

author: ledtester
author_rank: Super Contributor
timestamp: July 14, 2021, 05:43:14 pm
content: The GBU 1001 rectifier will work.QuoteThe datasheet says you won't need an heatsink if you keep the current under 3.2A so maybe that's an option.QuoteYour 25-0-25/4A transformer should be able to maintain 50V RMS across a load when supplying 4A of current.The open circuit voltage will, of course, be higher. Transformers also have a voltage regulation parameter -- a percentage -- which describes how much the voltage varies from full load to no load.

author: TimFox
author_rank: Super Contributor
timestamp: July 14, 2021, 06:06:36 pm
content: A good free software package for calculating traditional power supplies (transformers, diodes, capacitors, optional inductors) is "PSUD2", written by Duncan Labs. Seehttps://www.softpedia.com/get/Science-CAD/PSU-Designer-II.shtmlNote that in this software, which includes models for popular rectifier diodes, both solid-state and tube, the transformer is specified by its open-circuit (unloaded) voltage and equivalent series resistance.Catalog data for transformers usually specify the output voltage at a specific current, and possibly efficiency. With those values (or an estimate for the efficiency), one can calculate the open-circuit voltage and resistance.

author: Napiza
author_rank: Newbie
timestamp: July 15, 2021, 10:46:13 am
content: Quote from: SuzyC on July 14, 2021, 05:39:12 pmThanks!!1) That reverse voltage is less if i only use only one secondary winding no? Would in that case the choosen bridge be overkilled?2) Thanks for all the advices, I would take them into account, I was also thinking on including thermal paste in the contact. First I will try to attach to the chassis as you say.3) Thanks, it has sense, I now don't know where my doubts come fromThanks SuzyC!!

author: Napiza
author_rank: Newbie
timestamp: July 15, 2021, 10:52:14 am
content: Quote from: ledtester on July 14, 2021, 05:43:14 pmThank you very much for your reply ledtester!!

author: Napiza
author_rank: Newbie
timestamp: July 15, 2021, 10:54:50 am
content: Quote from: TimFox on July 14, 2021, 06:06:36 pmSo useful! I'm going to download it, I'm sure it will help me a lot, thank you very much TimFox