Variable DC power supply

Submitted by Denis on Fri, 04/17/2020 - 00:43



because i am a beginner i need a little bit of help from you guys. I have fixed power supply model PS1303 it was fixed to 13.8V and i have added to it ammeter and in inside was small pottentiometer 470k for adjusting voltage from 12 to 16V. I replaced that with B500K and now i can adjust my voltage from 6.8 to 25V.I also for good measure replaced caps that were 100uF 25V to 100uF 35V.The question is can i somehow make it adjustable from 0-25V and what would be next step to do. Power supply uses transformer and a small board that converts AC to DC, also one 2N3055 transistor.

Thank you wery much for your help and opinions. 



The bridge rectifier gives a continuous pulsating DC signal. Then capacitors are used to filter the pulsating signal into a smooth non-pulsating DC. Finally, the voltage is regulated using a regulator IC.
A variable dc power supply is one of the most useful tools on the electronics hobbyist's workbench. This circuit is not an absolute novelty, but it is simple, reliable, "rugged" and short-proof, featuring variable voltage up to 24V and variable current limiting up to 2A.

  Joined November 07, 2019      124
Thursday at 04:25 PM

Can you provide any schematic or the internal circuit pictures? (Schematic is what that is mainly required).

But it is best to use proper buck-boost regulator additionally across the output for configuring it to a 0-25V power supply unit.


However, it can be done as far as transistor based switching device is concerned. It will be helpful if you provied proper schematic, if possible.

  Joined February 12, 2018      696
Monday at 02:11 PM

According to me directly using a variable resistor or potentiometer is not a good practice, because same thing you can do with a fan regulator. For this you need to attach a power supply regulator LM317, which is commonly used in DC variable power supply. Other thing you can do is that you can purchase a DC to DC buck converter for getting variable voltage supply. I suggest you to get more assistance from Sierra Software Ltd. technical support team about products and techniques.

  Joined May 23, 2020      48
Saturday at 02:49 PM