Each of the high current grounds must be short and have wide traces. As a
general rule, the common terminal of the filter capacitors should be the only
points where the other grounds couple into the high current AC grounds. The
only exception may be the control ground.
3.14.3 The AC Voltage Node
There is one node within each switching power supply that has the highest ac
voltage compared to the others. This node is the ac node found at the drain (or
collector) of the power switch. In nonisolated dc/dc converters, this node is also
connected to the inductor and catch (or output) rectifier. In transformer-
isolated topologies, there are as many ac nodes ...