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 carpenter 2nd April 2009 09:54 AM

Stacking power supplies

2 Attachment(s)
In Zen version 3, Nelson details a power supply. My question is this: can two positive voltage power supplies, such as described in the Zen article, be stacked, piggy-back?

I'm submitting a schematic that I simulated. According to Simetrix, the voltage is smoothed considerably with the second stage.

I'm seeking this particular method because I wish to use higher voltage (125v) on my mid-stage mosfets. I'm not very comfortable operating a chip voltage regulator at this extreme.

 carpenter 2nd April 2009 10:10 AM

2 Attachment(s)
Here's a voltage comparison:

 KevinHeem 2nd April 2009 09:24 PM

I don't think you need to(add a second stage)...try adding zener diodes or increasing the values to get your required voltage. Then try increasing and decreasing the values of C5 and C6.

 carpenter 2nd April 2009 10:23 PM

Did you look at the graph?

 KevinHeem 2nd April 2009 10:25 PM

Yes, can you explain it to me!

 woody 2nd April 2009 10:37 PM

Because the input impedience of the pass mosfet is so darn high
there might be less noise if you replaced the R34 resistor with
a ccs and replaced the zener stack with a resistor. No zener =
no zener noise.

 KevinHeem 2nd April 2009 10:38 PM

From my understanding of the circuit (limited) it is a capacitance multiplier, with the zener diodes holding the voltage constant. Is what you created a capacitance multiplier-multiplier.

 carpenter 2nd April 2009 10:44 PM

Quote:
 Originally posted by KevinHeem Is what you created a capacitance multiplier-multiplier.

Hahahaaa....

I think you're right...

 carpenter 2nd April 2009 10:48 PM

Quote:
 Originally posted by KevinHeem Yes, can you explain it to me!

The first stage has voltage variations of 0.120 volts, while the second stage only has variations of 0.005 volts.

 carpenter 2nd April 2009 10:52 PM

Quote:
 Originally posted by woody Because the input impedience of the pass mosfet is so darn high there might be less noise if you replaced the R34 resistor with a ccs and replaced the zener stack with a resistor. No zener = no zener noise.

The zener stack is what holds the voltage constant. Get rid of the zener stack and the voltage varies, yes?

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