schematic needed - Page 1
Forum section: electronics / projects

author: silly sausage
author_rank: Regular Contributor
timestamp: January 16, 2025, 01:53:54 am
content: I have just brought 2x L146 CB DIP-14 IC,they are an upgraded version of an lm-723 vreg ic,ie can take vin of 8v,i am looking for a schematic to build a adjustable psu,i have a big transfo with taps ranging from 2v to 37v plus and minus,I would like to cobble together a adjustable (circa) 0-50v wih tap swiching,can anyone help?,thanks tony.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 16, 2025, 02:20:50 am
content: not in the good thread sectionsome google fuu search would have given you some schematicshttps://www.eeweb.com/general-purpose-power-supply-by-l146-or-ic-723/you have datasheets too

author: silly sausage
author_rank: Regular Contributor
timestamp: January 16, 2025, 02:42:56 am
content: thats a good start, Thank you,any ideas of a suitable tap switching cct?, I ddid google for a l146 psu cct diag but found nowt,wonder why,google giving different results for different countries possibly?.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 16, 2025, 11:59:40 am
content: the l146 is known as the 723 high voltage if i may saythe best application would be to supply the chip with say 12-15vdc called floating voltage and you have a main supply of many ampsyou have many projects based on 723 who could give you ideas, or even ones with switched x-former secondariesat 50v x amps you know a psu like this may or will heat - dissipate a lot, current limiting is problematic if you want to go very low in the ma ranges, i have such project, tossed far far away and i'm not even sure i have the schematics anymore, it was complicated to implementyou have to know your xformer specs to build around it, how many amps / va / watts ....your design will be a mix of many things, trials and errors, i would build around the 723 and evolve it to include the l146 latersince its an unobtanium chip, i would be careful if they are genuine, i have the genuines mc1466, but never build something around themi simply bought already made psu's .... Kepco and Kikusui ones they are a mix of smps, phase controlled ac, dissipate less and more compactthe given schematic link is a good base and can be evolved further ... the current limittor is good but can be improved, you add an huge power diode in series of the power resistor and recalculate the limitter, that way on minimal settings it will trigger the limitting ...

author: Zero999
author_rank: Super Contributor
timestamp: January 16, 2025, 09:22:35 pm
content: I haven't heard of the L146.What's the application? Presumably it's for a laboratory power supply? I assume you require current limiting. A big downside of the 723 is the current limit is very rough and nowhere near accurate enough for a lab PSU. Another current amplifier is required for a more accurate current limit. Here's a thread with a couple of examples. Note that they're just suggestions, not complete designs.https://www.eevblog.com/forum/projects/lm-723-opamp-addon/msg5402774/#msg5402774Regarding the tap changer: there are many ways to do that. The simplest is to use a single pole, double throw switch and do it manually. It can also be automated using a comparator and a relay or transistor.Here's an idea I came up with awhile ago, but it's rather crude.https://www.eevblog.com/forum/chat/liniar-adjustable-power-supply/msg129099/#msg129099

author: silly sausage
author_rank: Regular Contributor
timestamp: January 17, 2025, 12:39:29 pm
content: Am i rite in thinking the max output current for the 60v version of this psu is 0 to 800 milliamps?, If so can it be beefed up using say 8x 2n3055 pass transistors with there emitter resistors?.