about ground in two power supply

[ashwini]

i am going to design power supply with two supply of 5volt and 12volt in one circuit,but with two different ground.how i design that one?

[AJISH ALFRED]

Hi Ashwini,

Any circuit, system or connected devices should have a single ground point. If you want two seperate ground wires at output, simply commect one end of the wires to the common ground point of the power supply circuit

[Pete Braven]

Hi Ashwini,

I think what you are trying to get is two isolated supplies off a single transformer?

It is technically possible by using a transformer with two separate, isolated secondary windings. Then separate voltage regulator circuits such as LM317 (variable) or LM7805 and LM7812, which would give isolation of both the positive and negative side of each output.

You would need to have something like a 0 – 12 + 0 – 12 transformer with a full bridge rectifier on each winding.

It’s an odd configration but one which used to turn up on old televisions to keep the HT circuits isolated from the rest. Basically we didn’t want to be touching anything remotely connected to 25KV,.. because it hurt!!

[Author]

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