Compensating for PS parasitic capacitance

[pooge]

It is known to select the orientation of supply lines to the primary of a power supply transformer to minimize the parasitic capacitance to ground, and thereby the ground current.

While this is all well and good, it doesn't eliminate it. Why not ADD capacitance to ground of the appropriate value to balance out the parasitic capacitances, and reduce the ground current due to this effect to zero?

[Sch3mat1c]

Maybe if it's push-pull. And the harmonics are in phase. Which, unless you wound your primary out of coax, they almost certainly are not.

These things are hard to predict, so outright shielding is more effective. Most of the time, bigger capacitors (1-4.7nF) are added between grounds to shunt the noise, hoping that brute force overcomes. It passes tests, so I guess it works.

Tim