Voltage multiplier

Mooly · 2010-02-20 8:38 am

Don't go away... I'll post a picture and then delete it

Mooly · 2010-02-20 8:46 am

Question for you ?

Is the 48 volt supply supposed to fully float ? The diagram clearly shows the "ground symbol" as being the same ground for the 48 volt supply and the lower dual supply.

Are these meant to be one and the same as shown ?

Mooly · 2010-02-20 8:59 am

Did you get the diagram showing the wiring ?

argonrepublic · 2010-02-21 3:19 am

Thank you mooly for extenstive teaching in this area. I stared at the diodes for a while and then came back to it. Voltages are way up now but for some reason, my regulators became inactive after changing transformer secondaries and closing all four diodes. I did further homework and learned about protection diodes on regulators. This project has become loaded with lessons.

Mooly · 2010-02-21 7:20 am

Have you got it to work then ?

argonrepublic · 2010-02-25 2:49 am

Wow this is a strange circuit I have everything working. I was having some difficulty getting my second circuit up to 48Volts. Now that it is up to 48 Volts, the LM317 is only allow a maximum of 35Volts out. I had the same issue with LM337. It only works properly when incorrectly wired. It is a Fairchild. I had to swap inputwith output to get it to provide max rail voltage.

Mooly · 2010-02-25 7:48 am

Strange in the way it's drawn yes.

Looking closer at the diagram the pin outs for the LM337 are labelled wrong. Also it's not really "gnd" it's the "adjust" pin and that is pin 1, not pin 2 as shown.

Good you have got it working

argonrepublic · 2010-02-25 3:05 pm

I actually wired them in accord with Fairchilds datasheet. I guess I am making progress so I will just take my time and keep learning until I understand why my circuit is acting the way it is.

ginetto61 · 2020-11-20 11:07 am

Hi ! i found this old thread on voltage multipliers and i thought reasonable to attach here my kind question

i do not know if what i have attached is that of a voltage multiplier schematic

I really need some help to understand what those two 2sd667 do the DC voltage ... do they increase it ? how much ? how the multipligation factor can be calculated ?

If someone can direct me to some explanation of this circuit i would be very grateful.
I would like to increase the Vgain even further to mod a unit.
But i do not know if i have to change resistors and bjts with more powerful/higher volatge ones.
Current need about 1A absolute max ...
Thanks a lot to anyone
Have a nice day
gino

Vovk Z · 2020-11-20 3:54 pm

TR1 is a main active element of an active low-freq filter (a cap multiplier). TR2 is just an overcurrent protection.
To make it work up to 1 A you have to set up that protection to a bit higher than 1 A.
Ube of any bipolar transistor is about 0.5-0.6V when it starts to open, so R4 = 0.5V/1A = 0.5 R.
So, you may begin with R4 = 0.47 Ohm 1W.
You have to decrease the value of R5, of cause, too.

ginetto61 · 2020-11-20 4:20 pm

Vovk Z said:
TR1 is a main active element of an active low-freq filter (a cap multiplier). TR2 is just an overcurrent protection.

Hi ! thank you so much for your kind reply and very helpful advice.
Please let me elaborate a little. I have found this schematic and i wanted to understand what is the function of the circuit included within the dotted line
So it filters the ripple without increasing the incoming voltage. Great !
I do not think that it also regulates the voltage because i do not see any zener
can a voltage regulation function be added maybe placing a zener diode at TR1 base ?

To make it work up to 1 A you have to set up that protection to a bit higher than 1 A.
Ube of any bipolar transistor is about 0.5-0.6V when it starts to open, so R4 = 0.5V/1A = 0.5 R.
So, you may begin with R4 = 0.47 Ohm 1W.
You have to decrease the value of R5, of cause, too

Thanks a lot, I have understood No problem. I said 1A but it could be much less actually It is for preamps. When i will have the current i will calculate the R as you instruct.
There is a mirroring negative part with 2sb647 complementary parts to get the negative rail.
Is it possible to add V regulation also ?

Sorry .. i understand only now that i am OT ? what i have to search ... cap multiplier ? sorry again

Vovk Z · 2020-11-20 6:31 pm

Yes, you may add a Zener in parallel to C3 or after R3. The filtering effect will lower but it will regulate a voltage with a Zener stability.

ginetto61 · 2020-11-21 8:25 am

Vovk Z said:
Yes, you may add a Zener in parallel to C3 or after R3. The filtering effect will lower but it will regulate a voltage with a Zener stability.

Hi again, in understand now that my question was completely OT and i feel sorry for that.

Anyway i end here saying thank you very much to you. I am very interested in AC ripple filtering techniques applied in particular to smps.
I already knew of passive filters like RC or LC or more complex combinations of L, R and C. I knew nothing about active filters i will be trying to learn something, for instance the advantages of active versus passive filtering. I understand that the circuit that i have attached acts also as a cap multiplier ? so smaller caps can be used with an enhanced effect ?
Thanks a lot again. Have a nice day, gino

Voltage multiplier

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