Sense Wire on a powersupply

[jrz126]

I have a Power-One Linear 5V supply that I'm planning on using as just a benchtop supply. The unit has 5V sense connection, which should be connected at the load so that the supply can adjust for any voltage drops in the wires. (I think thats how its supposed to work?). Right now I have this sense wire connected to +5V at the supply and Im reading 5.5V. Can I just throw a pot or something on the sense wire so that I would be able to achieve an output alittle closer to 5V?

 

[rizzo]

Hello JRZ126,
I think that if you place a trimmer on the feedback, you can only make the power supply to see less voltage, so it will try to increase it. No good.
1) Have you tried to load a little the supply, e.g. with a resistor? If you tested it with no load or very light load, this could be the reason why you get the excess 0.5V. Some power supply tend to go higher in output voltage when too lightly loaded.
2) I do not know this brand of power supply, but there could already be a trimmer, inside the circuit, to adjust the output.

Good luck

Ezio

 

[JimB]

Usually there are sense terminals for the +ve and -ve sides of the output from the PSU, If you dont want to use remote sensing just connect the +S to +ve output terminal and -S to the -ve output terminal.
It is also usual for there to be a low value resistor (10 to 100 ohm) built into the PSU and connects the sense terminal to the output terminal. The idea is that if the sense wire becomes disconnected, the sense will still see the psu terminal voltage and regulate at a sensible level. If the sense is open circuit, the output could rise up to any value and damage the load, if the load is sensitive to over voltage.

All the PowerOne PSU I have seen have a voltage adjustment pot on the circuit board somewhere.
As Rizzo says, dividing the output before feeding it back to the sense will just give you a higher output voltage.

JimB

 

[Dean Huster]

Most of the modular supplies I've seen (i.e., those made by Lambda and Hewlett-Packard) have the voltage adjustment as a screwdriver adjustment on the rear panel. Certainly +5.5 volts is not right. Unless you intend to have a high current application going that runs the supply on its high end for current supply, jumpering the sense and output connections and using 2-wire operation on your bench makes the most sense (oooh!). It's in your best interest to search around the Internet or contact Power-One for a manual for your particular model. There's nothing nicer (well, almost) than having an operator's and/or service manual for all of your equipment.

Dean

 

[jrz126]

There were a couple of pots on the circuit board, I'll try playing with them sometime tonight. Thanks.

 

[JimB]

There were a couple of pots on the circuit board, I'll try playing with them sometime tonight. Thanks.

If it is just a single output PSU, I think you will find that one of the pots is a voltage adjustment, and the other is a current limit adjustment.

JimB