Hello,
I am looking to cobble together a cheap bench power supply. As you're probably aware, basic buck or boost/buck circuits are readily available from China via eBay or direct via AliExpress. I'm looking to create a supply with steady 5v and 3.3v outputs, and a a variable 0-30v output with constant current control. I want to use spare laptop power bricks as my input source to the voltage regulators.
I see Earth ground as a separate banana socket on most bench power supplies. Assuming that somewhere in the input path there's an isolation transformer, what's the use of the ground?
I would like to have a common circuit ground between my 3 regulators. The problem is, the constant current regulator has the sense resistor on the ground side. Thus I can't tie them all together. However, if I use 2 separate bricks as input, my problem is solved (assuming the two power bricks are isolated from earth ground). Is there any danger with tying together the grounds of two laptop bricks? Of course, in my idea one of the grounds appearing at the output will be through the sense resistor, so I'm actually tying together the grounds through a 0.5 ohm resistor. I wonder if I could end up creating a ground loop or something and fry the resistor out.
Thanks.
I am looking to cobble together a cheap bench power supply. As you're probably aware, basic buck or boost/buck circuits are readily available from China via eBay or direct via AliExpress. I'm looking to create a supply with steady 5v and 3.3v outputs, and a a variable 0-30v output with constant current control. I want to use spare laptop power bricks as my input source to the voltage regulators.
I see Earth ground as a separate banana socket on most bench power supplies. Assuming that somewhere in the input path there's an isolation transformer, what's the use of the ground?
I would like to have a common circuit ground between my 3 regulators. The problem is, the constant current regulator has the sense resistor on the ground side. Thus I can't tie them all together. However, if I use 2 separate bricks as input, my problem is solved (assuming the two power bricks are isolated from earth ground). Is there any danger with tying together the grounds of two laptop bricks? Of course, in my idea one of the grounds appearing at the output will be through the sense resistor, so I'm actually tying together the grounds through a 0.5 ohm resistor. I wonder if I could end up creating a ground loop or something and fry the resistor out.
Thanks.