230V AC to 12V 3A conversion without transformer ?. - Page 1
Forum section: electronics / beginners

author: sangar
author_rank: Regular Contributor
timestamp: February 11, 2019, 05:12:26 am
content: Hello All,I need to design a power block to supply my processor board and it should be a compact one...The input will be 230V AC and output to be expected is 12V 3A. I have seen some reference design from Monolithic systems for this, it seems that >10W needs a transformer...If it is right, what are the reasons which require a transformer for >10W supply design...Please suggest.Thanks,Sangar

author: Ian.M
author_rank: Super Contributor
timestamp: February 11, 2019, 05:22:51 am
content: Safety + capacitive droppers have horrible power factor and no load dissipation greater than their max output power.Do what everyone else does and buy in a SMPSU power 'brick' with the required output voltage and current and all the safety approvals you need for your intended markets. A 12V 4.1A (50W) SMPSU should be a commodity item as that voltage is commonly used in LED and Halogen lighting systems.

author: BravoV
author_rank: Super Contributor
timestamp: February 11, 2019, 06:13:30 am
content: Try Vicor.

author: Zero999
author_rank: Super Contributor
timestamp: February 11, 2019, 10:06:10 am
content: Quote from: Ian.M on February 11, 2019, 05:22:51 amYes, typically a SMPS is used, which does have a transformer, but it works at a much higher frequency, than the mains, so can be a tiny fraction of the size of a bulky mains transformer.Beware, lots of halogen lighting PSUs are merely transformers driven by a Royer oscillator. They're unsuitable for powering most electronic circuits from because they output 20kHz to 200kHz modulated by double the mains frequency and commonly have a minimum load current requirement.Here's an application note, showing the typical schematic, for educational purposes.https://www.st.com/content/ccc/resource/technical/document/application_note/e5/88/46/11/35/8c/4a/bf/CD00003902.pdf/files/CD00003902.pdf/jcr:content/translations/en.CD00003902.pdfA 12V LED power supply designed for LED strip is a better option. It will output steady DC and a suited for most electronic circuits.

author: sangar
author_rank: Regular Contributor
timestamp: February 11, 2019, 01:26:43 pm
content: Hi All,Thanks...Our requirement is that the power module to be designed should not exceed the board size of 50mm x 50mm and be bulky...As far as I searched, I couldn't find any power module which is within 50mm x 50mm...If one can design it in the given size, I am asking you to share the sources that guide me to design...Thanks,Muthu

author: Doctorandus_P
author_rank: Super Contributor
timestamp: February 11, 2019, 03:32:12 pm
content: Power scales with size.Why generate 12V for a "processor board"3V3, or maybe even 5V seems more appropriate.When you look at Ali, "open frame" and "single output" seem to be good magic words for starters:https://www.aliexpress.com/wholesale?SearchText=open+frame+50W

author: alex-sh
author_rank: Regular Contributor
timestamp: February 14, 2019, 10:28:32 am
content: Quote from: Doctorandus_P on February 11, 2019, 03:32:12 pmDid you try any of these Ali open frame PSUs? My biggest problem is ripple/noise and power for any processor board must be very clean.

author: mariush
author_rank: Super Contributor
timestamp: February 14, 2019, 10:43:22 am
content: Why do you need 12v?Do you need it just because you have a fan or you have a small number of components that need 12v? You may be able to use a step-up regulator on your board for those parts and use a lower voltage power supply otherwise?Do you use linear regulators to get the voltages you want? If so, maybe you could change them for step-down/buck regulators and use a higher input voltage like 18v..24v for higher efficiency, and so you may not need 30w+ of power.