Power Ground and Sigan Ground difference

hi

what is the difference between Power Ground and signal ground in DC DC converters?

What will happen if we connect them together?

Please explain in detail.

Power Ground is the net that typically represents the negative voltage of the power stage. Since high and "noisy" currents flow in this GND it is not recommended to use it as a reference for digital and analog circuits such as the ones present in the control part of the DC/DC converter. This is why the control part is connected to the "signal ground".
Depending on the converter Signal and Power grounds can be connected or not:
- Isolated converters may have signal and power ground isolated from each other.
- In non isolated converters Signal and Power grounds are typically connected but ONLY IN ONE POINT in the PCB. This is crucial to avoid ground current loops that would worsen the converter performance.
- In low power/low voltage converters Power Ground and signal ground can be the same, typically refereed to a common ground plane.

Ernest

It's fine if the control ground and power ground are connected to each other, so long as it's done in a way that minimizes interference between the two. Mainly you have to prevent the switching currents (and preferably DC currents) from flowing through the control ground plane. This is just a matter of good PCB partitioning.

thanks for the reply.

" In non isolated converters signal and power grounds are typically connected but ONLY IN ONE POINT in the PCB. This is crucial to avoid ground current loops".

Does it mean providing parallel ground connection?
Please clarify.

It means they should be connected only in one phisical pont (i.e. only one pcb track connects both grounds).