Adjustable Linear power supply with split rails and/or 0-50V ideas ? - Page 1
Forum section: electronics / projects

author: lordvader88
author_rank: Frequent Contributor
timestamp: February 01, 2018, 10:48:53 pm
content: I have a 100W 1.3A transformer with a centertap, -26/+26. I'm not ordering anything for now. This is just for basic beginner low-V and C bench stuff, so I don't care I want to make a few things like , 0-24 or +24/-24, or 0-50V PSU. I found out the LM723 not really used for split rail. And neither is LM317, and I don't have LM337 (-ve) version.I haveNPN TIP42, TIP142 DarlingtonsTL431 adj. reflots of LM35879XX -ve reg'sI don't have any PNP power transistors, BC558 is probably biggest PNP I haveSo what are some good adjustable series pass regulator circuits uses opamps and pass transistors ? I want to build something (I'm probably going to settle and use a 32V trans for tonight and make a LM723 PSU, but for this weekend.........I want to use that CT transformer for stuff.

author: jbb
author_rank: Super Contributor
timestamp: February 01, 2018, 11:24:49 pm
content: I would suggest a dual supply (0 to +-24) because a lot of analog circuits like dual supplies, and you can always connect across both rails to get 0 to 48V).It depends a lot on what you’re doing, but I find it rare to go beyond +-15 for general purpose stuff.What other taps do you have on your transformer?

author: lordvader88
author_rank: Frequent Contributor
timestamp: February 02, 2018, 12:05:05 am
content: I have an analog VHF/UHF tunner and some other little 1970s TV block sections that take 24V. Now I do have 24V SMPS, but thats noisier. But this is for general stuff, world domination, etc.

author: ocset
author_rank: Super Contributor
timestamp: February 03, 2018, 10:28:07 am
content: here are some LTspice schems which look like relevant to your wishes.Ones a seires pass lin reg which shows how it works in annotation.I know its not the same parts as you have, but they are in many ways pretty much the same.I also attach ltspice quik start.Ltspice is a fre download

author: John Heath
author_rank: Frequent Contributor
timestamp: February 03, 2018, 02:19:05 pm
content: There is also the bin diving or discount store approach. Find an old stereo amp looks like it has some beef , 50 to 100 watts. There in is all the parts you need for a split rail 30 to 50 volt power supply. The audio output transistors can be used to regulate voltage and current. A second option is an old computer. That power supply is +5 - 5 +12 -12 fixed. This is good for most op-amp and logic projects.

author: David Hess
author_rank: Super Contributor
timestamp: February 03, 2018, 04:40:28 pm
content: The TIP42 is a 40 volt, 6 amp, and 65 watt PNP power transistor so you do have some big PNP transistors. The TIP142 is a 100 volt, 10 amp, and 125 watt Darlington NPN power transistor.The 7905 has a maximum input voltage of 25 volts so it is not going to be real useful with that transformer without help.Two TIP42s can be paired up to make a Darlington PNP without about half of the power capability of the TIP142 for a fully complementary design.The tricky part is that the 32 volt LM358 had a somewhat limited supply voltage range for a 26 volt AC secondary which produces about 36 volts peak. The TL431s can be used to make low power regulators to supply the LM358s.There is nothing to preclude using the same polarity transistor, either the PNP TIP42s or the Darlington NPN TIP142s, for both sides.