Author Topic: Clarification and comments on power supply schematic  (Read 1090 times)

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Offline d4n13lTopic starter

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Clarification and comments on power supply schematic
« on: August 10, 2018, 12:58:15 am »
Hi,
I'm starting with semiconductor and my goal project is to make my own variable power supply and understand how it all works. I've been searching for schematics (without ICs, I attached one schematic). Here the supply's output is taken from the emitter of the power transistor. I think it resembles a common base configuration but in that configuration the emitter is supposed to be the input not the output, so can someone explain how is it working here?

Also any comments you may have on this schematic would be appreciated.
 

Offline JS

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Re: Clarification and comments on power supply schematic
« Reply #1 on: August 10, 2018, 01:11:56 am »
It's a common collector configuration, I think that should help you to continue, feel free to keep asking.

JS
If I don't know how it works, I prefer not to turn it on.
 

Offline d4n13lTopic starter

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Re: Clarification and comments on power supply schematic
« Reply #2 on: August 16, 2018, 05:11:11 am »
I think I understand how the circuit works now, except I don't see why they used a second transformer for the reference voltage? what advantage can it have over setting Vref directly from the main transformer?

I reorganize the schematic for clarity, it looked terrible before.
 

Offline glarsson

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Re: Clarification and comments on power supply schematic
« Reply #3 on: August 16, 2018, 08:07:34 am »
The second transformer is used to create a negative voltage.
 

Offline rstofer

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Re: Clarification and comments on power supply schematic
« Reply #4 on: August 16, 2018, 01:54:33 pm »
The second transformer is used to create a negative voltage.

Without which you can't set the output voltage close to 0V.
 


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