Good day @Ian.M
Sorry, on the schematic I just wanted to know if the layout was correctly understood as worded, I just used an arbitrary valued resistor.
That is getting quite close to the maximum voltage an LM317 can tolerate, combined with the negative voltage on the adjust pin, it's getting uncomfortably close.
This is most certainly very true.
I have factored in a +10% increase in voltage and reach a value of 39.20Vdc again, these are all perfect world values as there are still losses involved in converting to dc.
Transformer secondary unregulated AC output at the upper tap is 24.4Vac x 1.1 = 26.84Vac then taking that x 1.414 = 37.96Vdc. + 1.25 = 39.20Vdc. This is not including any loss in wiring voltage drop across diodes etc..
The LM317's data sheet says it can regulate up to 37V? I understand that these are maximum voltages, but, as I "theoretically" do not want to go that high I should remain with in this margin, again, "theoretically".
But, if I am to look at all that has been said it would seem that I would face exactly the same challenges with the LM723, not only that, but the cost?
The LM723 also has only a 40V limit, if all this top end voltage is of a danger to the LM317 is it not the same then for the LM723?
I also do understand that there is a big difference in regulation (LM723 being a lot better) but, with that comes the price tag.
The LM723 again is not locally available, I will either have to wait for it to be imported which could only be next year, or it has to be specially ordered at a minimum of 10pcs, and in my money at 50N$ a piece
that means 500N$ out of pocket (not including shipping, which as already stated is just ridiculous), the LM317 is here, available, and cost me 15N$ a piece, again, I am in Africa, which makes getting hold of certain items not viable The LM 317HV is also not locally available.
As I am not using the LM317 to directly supply the main current to the output but am rather shunting the current via a set of power transistors, would it help if I could "limit" the the input voltage "AFTER" the dropper resistor to the LM317? Say for example by using a TL431 or possibly zener diodes to regulate to 33V, do you think this could be a viable solution? Obviously using the correct transistors to supply the needed current to the LM317.
I urge all who read this to try and understand that we (in certain parts of Africa) do not have a lot of the luxuries that many of you take for granted, eg. quick door to door deliveries, LES's that stock almost everything you want, or, that will order in anything you need at a decent and affordable price, I design with what is available to me, here in Africa, often times import, depending on the product can cost up to 2x what the product itself costs, please bear this in mind and do not take what you have for granted and think that i am afforded the same amenities as you have available to you.
Yes, there is a capacitively coupled negative rail, from this the LM337 will only have to "regulate" to the required 1.25v.
On that note, addressing some of the other comments.
I am not natively English speaking, I work in and live in a natively speaking Afrikaans population, This means: THAT I DO NOT ALWAYS WORD MY SENTENCES CORRECTLY!!
If all you want to do is attack my poor command of the English language then please keep your comments to yourselves.
For the constructive and meaningful parts of your explanations for which there were answers to the asked questions, I thank you.
Regards.
Charles