Electronics > Beginners
Linear PSU with modern components, will it matter ?
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digsys:

--- Quote from: coppercone2 ---  What happens to noise when you start messing with magnetic feedback paths? ...
--- End quote ---
Funnily enough, there is no noise .. as such :-)  What you get is AC distortion in V and I ie it is not a pure sine wave anymore BUT it is still an AC waveform,
so you don't have to worry about switching "spikes", harmonics etc  It is doable ie a reasonably clean AC V and I, but you need to know a lot about core
magnetization / leakage / etc etc Actually, even though we got it pretty good, we abandoned it for other ideas :-)  .. much simpler
Magnetic feedback is used in many systems - google "Transformer magnetic feedback" Images for lots of ideas ... gl
coppercone2:
I wonder if LT  or AD ever wanted to make a LT4320 version that will run directly off mains

I think its a bad idea, but I always wanted to experiment using it rather then a diode bridge.

I found the part before I had a SA and RF gens/amps then I forgot about it for a while now it might be time to do some comparisons with various DC powered precision circuits I have.
BravoV:

--- Quote from: digsys on December 15, 2018, 05:34:11 am ---After many years designing linear P/Supplies, mostly Intrinsic / mining etc, this was my goto design for several years -
(obviously not the full design, but main excerpts) - 0-36VDC op, 0-20A+ op: MAX loss - Bridge and regulator = 0.8V (best min was 0.6V, but I left headroom).
NO fan, very minimal heatsink ! ~95% efficiency (not including transformer) .. not bad for linear :-)  220-260V ACin
Original design had a multi-tap transformer (lots of taps), then played with magnetic feedback, resonant circuits etc .. but a completely linear circuit !
One day, I'll see if Daves capacitance multiplier works :-) ... oddly enough it has a micro, but just for the front end :-)
So, can Linear P/Supplies get better ?? Shit yeah !!

--- End quote ---

Digsys, thanks, any chance you share the whole schematic ? Including the tap switcher if you mind.

Sorry, is that with adjustable current too ?

I can see you're still using that venerable LT4320 there.  ;)
digsys:

--- Quote from: BravoV ---  ... any chance you share the whole schematic ? Including the tap switcher if you mind ... is that with adjustable current too ?
--- End quote ---
Tricky situation. It was 1 of many contract designs ... then got sacked after several years :-) (long story) .... never paid for R+D or other "trades" ...
With all that, I don't want to risk any more animosity ... circuit operation theory, though, is common knowledge -
Run a small dual 5-8VAC, say 50mA transformer to power logic, REF 0V, and an isolated 6-12V high side FET driver rail
Use a small micro, with A/Ds to monitor AC V and I, and DC V and I. Then depending on Vop, switch in the respective winding, using the bridge type FETs.
Have this pre-regulator on a separate PCB, with it's OWN storage caps. Then, IF you want to get fancy, "active feed" the MAIN storage cap that supplies the
regulator PCB. At low current, it doesn't matter if Vin_Reg is a bit higher, as power dissipation will be low. Keeping the Vreg cap at an ideal, low ripple voltage
is the "tricky" part :-) .. but then, working that out, is the challenge :-)  In one 10A design, I believe I got ~97% efficiency .. not bad for linear (-Trx).

--- Quote --- I can see you're still using that venerable LT4320 there.  ;) 
--- End quote ---
Ahhh yeah, didn't I send you a couple boards way back? Did you ever use them? Useful? It's a DAMN fine IC !!
BravoV:

--- Quote from: digsys on December 15, 2018, 10:47:57 am ---
--- Quote from: BravoV ---  ... any chance you share the whole schematic ? Including the tap switcher if you mind ... is that with adjustable current too ?
--- End quote ---
Tricky situation. It was 1 of many contract designs ... then got sacked after several years :-) (long story) .... never paid for R+D or other "trades" ...
With all that, I don't want to risk any more animosity ... circuit operation theory, though, is common knowledge -
Run a small dual 5-8VAC, say 50mA transformer to power logic, REF 0V, and an isolated 6-12V high side FET driver rail
Use a small micro, with A/Ds to monitor AC V and I, and DC V and I. Then depending on Vop, switch in the respective winding, using the bridge type FETs.
Have this pre-regulator on a separate PCB, with it's OWN storage caps. Then, IF you want to get fancy, "active feed" the MAIN storage cap that supplies the
regulator PCB. At low current, it doesn't matter if Vin_Reg is a bit higher, as power dissipation will be low. Keeping the Vreg cap at an ideal, low ripple voltage
is the "tricky" part :-) .. but then, working that out, is the challenge :-)  In one 10A design, I believe I got ~97% efficiency .. not bad for linear (-Trx).
--- End quote ---

Understandable, infact thanks for introducing that Micrel chip.

How its perform, say with switcher pre-regulator instead of using step-down transformer ? Did you ever try this combination ?


--- Quote from: digsys on December 15, 2018, 10:47:57 am --- I can see you're still using that venerable LT4320 there.  ;)
Ahhh yeah, didn't I send you a couple boards way back? Did you ever use them? Useful? It's a DAMN fine IC !!
--- End quote ---

Yep, used it at few projects, they perform flawlessly !  :-+
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