[FrankSL]

Hi all,
This is my first post on the new site, my nickname on RO was Wes.
I have a question for Bo Hansen or anyone that can see the schem of his power supply on his site:
PSU

I can't undertand how the voltage doubler works in the 48V section. To my little understanding of these circuits it looks that the diode that is in series with the 100uF cap on the left should be placed after the other diode, i mean connected between the cathode of the vertical diode and the transistor collector.
Can anyone explain me this?
Thanks,
Frank

[NewYorkDave]

That's a classic half-wave voltage doubler circuit.

Here's two of many webpages that explain voltage doublers:

http://www.tubecad.com/january2000/page14.html
http://www.tpub.com/neets/book7/27m.htm

[Bo Hansen]

Hi Frank,

As New York Dave say, it is a usal classic half wave voltage doubler, and there are also half wave rectification for the +/- 18 voltage.
Why only half wave rectifcation, when full wave have better ripple rejection
Because the thought was that a usal 24 volts AC wall plug-in adaptor shall be the AC feed to this power supply, and to get +/- and phantom voltage are the half wave rectification the best way to do this.
The regulation is ok in this case because one API card draw very low current and after the 78/79 regulators and the phantom pass transistor the voltage is clean and nice.

--Bo

[FrankSL]

Hi,
many thanks for the links and explanation. Unfortunately my ideas are not that clear... :grin:
 I knew how the circuits in those links you gave me work, they are standard voltage doubler as you said.

Now please look at Bo's circuit, it has a cap and diode in series... I just can't understand how the cap can charge with that diode in series... circuits in those links show the diode placed between the other diode and the output... I can post a picture of what I mean if you want.
I even simulated that circuit and it looks that the output voltage is not correct...
Thanks,
Frank

[FrankSL]

Wooops....
Sorry, I'just discovered that I had an old version of Bo's page saved on my disk... It must have been corrected after I saved it, now it looks good to me also... :grin:
Thanks and sorry for my mistake,
Frank

[Bo Hansen]

Frank,

Maybe I understand your problem now,

In January when I display this schematic for the first time I discover a drawing fault in the voltage doubler, the first diode was connected in series with the capacitor and not to the AC/0V ground that it is now (since february)
So maybe you have printing out this schematic under january and refer to this old schematic when we discuss this matter now.

Here are the valid schematic since february 2004
http://w1.316.telia.com/~u31617586/

--Bo

[Bo Hansen]

Frank,

Ah, just now in same time I post my last message, you have discover the problem your self.

Sorry, for the drawing fault from the first time.

--Bo

[FrankSL]

No problem Bo, thanks for the quick help!
Frank

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