[HACK]Adding a constant current pot to a power supply to work as CC CV (TL494)?

[MikeLemon]

Hello,

So I have this SMPS unit:



and would like to add a variable resistor to a TL494 based power supply I've seen other people do it but on another types and would like to know how to do it in here where is the resistor that controls the current limiting and what value pot should it be replaced with?
Help is very appreciated.

Thanks for your time.



Here is the reference schematic in the datasheet.

[David Hess]

A 1 kilohm variable resistor in place of R1 would do it.

[MikeLemon]

A 1 kilohm variable resistor in place of R1 would do it.

Aight Thanks I'll try it out and send a feedback.

[MikeLemon]

A 1 kilohm variable resistor in place of R1 would do it.

So I located that resistor on my PSU and it was 68KOhm so I replaced it with a 50KOhm Pot now when connecting a 2A load to it and turnin the pot to min or max it doesn't have any affect on voltage or current you sure it's that resistor?

Also what is the math for the current behind it?

[MikeLemon]

Hello,

So I have this SMPS unit:



and would like to add a variable resistor to a TL494 based power supply I've seen other people do it but on another types and would like to know how to do it in here where is the resistor that controls the current limiting and what value pot should it be replaced with?
Help is very appreciated.

Thanks for your time.



Here is the reference schematic in the datasheet.

[David Hess]

A 1 kilohm variable resistor in place of R1 would do it.

So I located that resistor on my PSU and it was 68KOhm so I replaced it with a 50KOhm Pot now when connecting a 2A load to it and turnin the pot to min or max it doesn't have any affect on voltage or current you sure it's that resistor?

Also what is the math for the current behind it?

That is the resistor on the schematic which can be used to alter the current limit.

Resistor divider R2 and R1 apply a 1 volt reference to the inverting input of the current error amplifier at pin 15.  When the voltage across R13 reaches 1 volt indicating that 10 amps are present, the current error amplifier takes over and limits the current.  Lowering the value of R1 lowers the reference voltage applies to pin 15 lowering the maximum current.

[T3sl4co1l]

I don't see a current transformer, nor an auxiliary power supply for the controller.

I doubt you'll be able to get much adjustable range before the controller starts hiccuping, and no such thing as CC operation.

Tim

[MikeLemon]

I don't see a current transformer, nor an auxiliary power supply for the controller.

I doubt you'll be able to get much adjustable range before the controller starts hiccuping, and no such thing as CC operation.

Tim

So you say leave it?

[T3sl4co1l]

If you want to go to great lengths, it could be used as a starting point, perhaps -- but if you just want a thingy, yeah, better to leave it.

Tim