Schematic for linear Current/Voltage regulator

I am making various little things to use a PP-1104B/G power supply for various purposes.

formatting link

One of the things that I would like to do is add a linear current and voltage regulator.

I found a very straightforward schematic in this PDF file

formatting link

on page 12. It seems to be adjustable with pots for both voltage and current and could use my Darlingron transistors that I already have.

Am I missing something and is this schematic a sensible one? Applications are voltage up to 35 volts, current up to 100 amps (but at much lower voltages). See description of the PP-1104B/G for its capabilities.

i
Reply to
Ignoramus11477
Loading thread data ...

It's a "sensible" generic description of a linear regulator. You'll need to think about heatsinking, because a linear regulator will dissipate (Vsupply - Vload)* Iload watts of heat. You'll probably need substantial heatsinks with forced-air (fan) cooling.

Reply to
Don Foreman

Don, thank you. These transistors are already mounted on a substantial heatsink (I would say 12x6x2 inches). Yes, I will forced air cool it. I will also mount a very conservatively rated thermal switch next to the transistor to turn off the device if it gets too hot, these are not too expensive.

What I would like, is end up with something simple that will work every day without glitches, and stop if it gets into trouble (like overheating).

The schematic on page 12 (see above) mentions some differential amplifiers, I would like to know what would be the easiest ones to use. There is also a diode and I would like to know if I can just use any general purpose one or I need something special.

Basically I would like to move from a general idea (like that page 12) to an actual schematic with parts and values etc.

If there is a general purpose "chip" that implements control of a linear regulator (apart from, that is not including, the big darlingtons), I would love to use it instead of cobbling components together. That ideal "chip" would have inputs for current and voltage control pots, maybe power supply and ground for functioning, and output for the darlingon.

thank you.

i
Reply to
Ignoramus13308

formatting link

I missed seeing the pots. That paper is really about what regulator IC to choose, rather than instruction on making your own regulator from discretes.

I would suggest getting an ARRL handbook -- they'll have a chapter on power supplies, along with some practical projects (but not any that go to 100A!). That should get you started, although you'll find out lots of interesting things about operating at 100A, I'm sure.

--
Tim Wescott
Wescott Design Services
 Click to see the full signature
Reply to
Tim Wescott

formatting link

Tim, did you look at page 12, there are resistor dividers for inputs to diferential amplifiers that, I think, can be replaced with pots.

Tim, I will get ARRL handbook and peruse it. Thank you.

i
Reply to
Ignoramus13308

All of what you desire is in the LM723.

You did forget the voltage reference (which comes for free in the LM723).

Google for LM723 datasheets and look at the example circuits. AoE also has detailed info in LM723 applications, as do the ham handbooks and TAB books from the past 3 decades.

Current limiting implies some choices that you'll have to make, especially sensing resistor and whether you need foldback current limiting or not.

I would recommend that you play around with low-current supplies before jumping in the deep end with (what is by my understanding your desire) a 100 Amp multi-kW dissipating linear supply!

Tim.

Reply to
Tim Shoppa

Ah. I was being hidebound -- I saw the dividers, but didn't see _pots_. You could replace those with pots, indeed.

I suspect that you'll want to use a circuit that's based on the 723, with lots of stuff surrounding it.

The manual for the power supplies you're looking at indicated that there is some sort of a regulator circuit already in place -- what's the matter with that one?

--
Tim Wescott
Wescott Design Services
 Click to see the full signature
Reply to
Tim Wescott

Tim, I printed the datasheet, looked at it briefly, this LM723 seems perfect! Even the voltage range is "just right"! The diagrams are very straightforward also! Supposedly there is even a way to have foldback, which would be super nice to avoid meltdowns of the darlington.

Seems like this LM723, a few resistors, a current shunt, a small cap, and my darlingtons should do the job!

Thank you!!!

Is Digikey item 497-4268-5-ND the right one (DIP package)?

As for multi-kW, the worst dissipation is limited by the fact that this will be fed from a 15 amp household breaker. (and I am tempted to install a separate breaker on this power supply limited to, say, 12 amp). At 12 amp, 125V, the most I can get is about 1.5 kW, which is not too hard to dissipate with a decent fan. I have a bundle of CLE2T2 caravel fans, but they are probably a little too big.

i
Reply to
Ignoramus13308

It is a voltage regulator only, it is a CV supply with no current limiting. The voltage regulator is good, with very low sagging at higher currents and 1% ripple. I looked inside that power supply, there capacitor bank reminds me of a Coke 12 pack. Plus voltage regulation only is in a range 13-19 volts and 26-39 volts, it would be nice to expand that.

Reply to
Ignoramus13308

formatting link

They have a whole book on the subject:

formatting link

LM723 is a good general-purpose chip, but realize that it can only regulate down to about 2 volts, unless you create a negative bias supply for it. There are a number of ways to work around this if it matters.

Don Foreman W0LAP

Reply to
Don Foreman

formatting link

Don, I cannot see why I would need a power source below 2v. If you are referring to it dropping about 2v (should be 3v or so, IIRC) from supply, that's fine witrh me. The datasheet for LM723 that I read today, goes in good detail about making various linear regulators with it with some nice features.

I will try to get a schematic on paper in a week or two (with values) and will post the scan.

i
Reply to
Ignoramus13308

formatting link

No, that's "headroom". The min regulated out of 2V, regardless of drop in the series pass semiconductor (which can be considerably less than 2 volts though not with an NPN darlington as pass element) is because the error amp inputs are not specified to work below 2 volts. Ability to control output voltage clear down to zero is useful when working with servomotors, among other things.

Reply to
Don Foreman

I just bought an ARRL handbook, see ebay item 130050716016. 2006 handbook with "cdrom" (which, I suspect, contains a bunch of MS Windows crap).

i
Reply to
Ignoramus16175

It may or may not. I do know it contains a lot of Linux crap, and some DOS crap and some Java crap. BTW the Linux - ham radio community is significant and vibrant. Amongst the Linux "crap" is some computer interfaces to convert HT or similar base into a digital radio modes. Uses the sound card for the modem.

--
 JosephKK
 Gegen dummheit kampfen die Gotter Selbst, vergebens.  
 Click to see the full signature
Reply to
joseph2k

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.