PASS like irf voltage-regulator

[lykkedk]

Hi. I know, this had been discussed a lot of time before, but i am in doubt of something i asked a long time ago.

When i 3-4years ago, was building my BoSoZ, i could not find torrrid's with 2x30 (i would not back then buy 2pcs. of 30v torids). Well, i bought a 55x2 torrid, and attached it to the bosoz psu (no modification's) giving me nice 60vdc regulated out, without any problem, except that the irf9610/irf610, was getting very very hot. I simply added big heatsink's for solution to this, and the bosoz had been working fine since then.

Grollin's back then told me, that i needed big sink's, cause of my 2x55torrid, but can somebody explain me why ??? As i see it the voltage out of the recitifier would be ~76v, having 16v down to the 60vdc regulated ??? what is the problem ???

Anyway, i have also this quistion... Right now, i am building a pass psu (like bozos psu), but the psu should give me out +36 / -36v DC. I have used a zener-string of 6pcs. 6,8v zener 3Watt giving me ~40,8v on that string. I am in doubt, what kind of torrid i should use... Should it be 2x40 or just my 2x55, i simply can't figure it out.

Thank you in advance.

Jesper.

[Zen Mod]

Originally posted by lykkedk
Hi. I know, this had been discussed a lot of time before, but i am in doubt of something i asked a long time ago.

When i 3-4years ago, was building my BoSoZ, i could not find torrrid's with 2x30 (i would not back then buy 2pcs. of 30v torids). Well, i bought a 55x2 torrid, and attached it to the bosoz psu (no modification's) giving me nice 60vdc regulated out, without any problem, except that the irf9610/irf610, was getting very very hot. I simply added big heatsink's for solution to this, and the bosoz had been working fine since then.

Grollin's back then told me, that i needed big sink's, cause of my 2x55torrid, but can somebody explain me why ??? As i see it the voltage out of the recitifier would be ~76v, having 16v down to the 60vdc regulated ??? what is the problem ???

Anyway, i have also this quistion... Right now, i am building a pass psu (like bozos psu), but the psu should give me out +36 / -36v DC. I have used a zener-string of 6pcs. 6,8v zener 3Watt giving me ~40,8v on that string. I am in doubt, what kind of torrid i should use... Should it be 2x40 or just my 2x55, i simply can't figure it out.

Thank you in advance.

Jesper.

smtms I'm not sure are you teasing us or you really don't know some basic things ........... ?

use 2x40Vac donut..... it's perfectly fine for series reg and 2x36Vdc output after reg


or use 2x55 if you have enough heatsinks and caps with enough voltage

[CheffDeGaar]

To get the preregulation DC voltage, take your transformer output voltage (55V), multiply it by square root of 2 (55V x 1.414) and substract some 2 Volts to account for the voltage drop in the rectifier bridge.
Then you get 75V7 DC before your mosfet. If the regulator outputs 60V, your mosfet will handle 75.7-60=15.7V. Multiply this figure with the current needed by the BoSoZ (in amps) and you get the mosfet dissipated power.
Compare it with allowed power on an IRF/TO220, and you'll see that heatsinking must be big

And starting from the opposite, take your output voltage, add 5V for regulator operation, add 2V for bridge losses, divide it by 1.414 and you get your AC voltage for transformer. For 36V, a classical 30V transformer will do.

Hope this helps

[lykkedk]

ZenMod... Please don't misunderstand me!, well if you see, the quotet message a 60v torrid would give even more heat right ???- This excatly i don't understand.

Then you get 75V7 DC before your mosfet. If the regulator outputs 60V, your mosfet will handle 75.7-60=15.7V. Multiply this figure with the current needed by the BoSoZ (in amps) and you get the mosfet dissipated power.

Why is Nelson using a 60v torrrid then, this dosen't make since, using theese calculations. I know the basic rule's... (i think ). But that the 'oppisite' of that calculation. ?

Thanx for replys anyway. Hope to get some more explanation's through!
Please bare with me then

[Zen Mod]

you know - your first post doesn't ring a clear bell in my head just because there are almost too much variations of BOSOZ ( mainly in neg voltage for PSU) so I'm almost always confused if I don't see exact schmtc ;
anyway....

if you use 2x40Vac donut for pumpkin reg ,then you'll have (lookin' at just one side ) after bridge and first cap bank:

40 x 1,41 = 55 to 56Vdc , including bridge losses ;

few volts down doesn't matter, when you wire load....... (active part of preamp) ;

so- difference is ,say 20V between input and output of reg ;

for one channel current consumption is 50mA (if I remember well ) , so dissipation is 20Vx50mA =1W per series mosfet.........

almost nothing

same calculations you can use for any reg you made , and things will be clearer to you,if not to me

[jacco vermeulen]

Originally posted by Zen Mod
for one channel current consumption is 50mA

Same same for bitsj of SoZ, even less.
Question is if lykkediki did not have a much higher bias level, which would be the primary cause of an overheated mosfet in the regulator.

[Zen Mod]

Originally posted by jacco vermeulen


Same same for bitsj of SoZ, even less.
Question is if lykkediki did not have a much higher bias level, which would be the primary cause of an overheated mosfet in the regulator.

dear Carrot Guru, do not confuse me more than I am already ........

he's makin' dreky now ........

without exact BOSOZ schmtc I can't tell anything ......... regarding BOSOZ

[lykkedk]

It's this voltagereguaĺator used in good old faschion bosoz
http://passdiy.com/pdf/balzenpre.pdf

I just modificated the zenerstring to 6x6,8v zeners = 40,8v and use a 55vx2 torrid, first attemp didn't succes... don't know problem right now.
Will try figure out later.

Jesper.

[CheffDeGaar]

A bit unfair from you to let us play a guessing game with so little clues.
Measure the Mosfet Vgs, the voltage drop across the 4K75 feeding the zeners, the current drawn by the bosoz, and do the maths to see where the current goes.

[lykkedk]

Sry... I wasen't expecting help (try myself this time) ...

Well at my first attemp, i had mounted a 3,3k resistor for feeding the zenerstring's, actually the regulator was giving me 36+ an 36- here so it might had worked. (I just dident try to load it with anything at this point) I was powering it down, because the 3,3k resistors (R101+R102) was getting hot. I then was fiddeling around with some other values here, but then it suddently stoppet regulating (2blown irf's i quess).

This is where i am now.

Maybe it's to much for the regulator to regulate down from 75v to 36v (~40v) The original bosoz psu only regulates down from 80v to 60v. That was mainly the reason i had lowered the R101/R102 down to 3,3k instead of 4,7k, i was thinking that the zeners needed more currency then. (see now, that it's not the case )

Magura just called me up on the phone (Thanx Morten) and helped me out, so i think i will find a sollution to this tomorrow or so... It shoulden't be so hard to make right ?

Thanx any! for helping me out, and i think cheffDeGaar is right about my bosoz causing the extra heat in my old regulator. The regulator when it's done, will surely be for dreking pumpkin as ZenMod 'guessed' hehe.

Jesper.