Simple 0 -100vdc bench supply circuit anywhere

Thread Starter

chucknnc

Joined Feb 12, 2015
8
I need a simple 0-100vdc supply for the bench, does not need to be regulated. I will be using a 3 amp powerstat autotransformer for control. I can't find a circuit anywhere on the web, every search turns up switching PS. What ever happened to the old time analog circuit websites that were there years ago?
I know this is simple and should only require a bridge, cap of proper value and bleed resistor, still a schematic/circuit of one would be nice.
 

Ian0

Joined Aug 7, 2020
3,280
The variac will give you 0-270V AC from a 230V input, so you need a 230V to 60V isolating transformer followed by a rectifier and smoothing capacitor to get 100V DC.
 

Thread Starter

chucknnc

Joined Feb 12, 2015
8
The variac will give you 0-270V AC from a 230V input, so you need a 230V to 60V isolating transformer followed by a rectifier and smoothing capacitor to get 100V DC.
Yep, got a isolation trans, but not sure what value cap or if I need a LC circuit. I have several 0-90vdc motor controllers so maybe that would be a better option, just need something that goes higher than my 40v lab supply.
 

crutschow

Joined Mar 14, 2008
27,759
got a isolation trans, but not sure what value cap or if I need a LC circuit. I have several 0-90vdc motor controllers so maybe that would be a better option
You do need the isolation transformer.
What type of output do those motor controllers have?

Otherwise use the variac, a diode bridge, and a large filter capacitor to get a DC output.
The size of the capacitor will be determined by the maximum current output, and the amount of ripple you can tolerate.
An LC circuit would reduce the ripple, but inductors of that size are large and expensive.
 

Thread Starter

chucknnc

Joined Feb 12, 2015
8
You do need the isolation transformer.
What type of output do those motor controllers have?

Otherwise use the variac, a diode bridge, and a large filter capacitor to get a DC output.
The size of the capacitor will be determined by the maximum current output, and the amount of ripple you can tolerate.
An LC circuit would reduce the ripple, but inductors of that size are large and expensive.
motor controllers are from industrial plant 120vac in 0-90vdc out, they were pulled from service as AC vfd's were taking over, it
looks like alot of weight with transformer and variac, althou I have plenty laying around, maybe I will reconsider a Chinese switching supply. Work bench is always overcrowded so that becomes a priority.
 
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