The present invention provides magnetic structure, particularly an isolation
transformer, which includes a shield to prevent radiation of electromagnetic interference
("EMI"). The magnetic structure includes a support structure, or bobbin, on which
are mounted windings formed from electrical conductors. The windings are electrically
connected to termination points, which provide the electrical interconnections
for the magnetic structure. A magnetic core can be included in the support structure
to provide optimal magnetic properties to the device. An EMI shield formed from
a metallic foil such as copper is wrapped around the winding to prevent the radiation
of EMI. The EMI shield is connected to a shield pin in the support structure by
a conductive strap such that the shield pin is electrically connectable to a fixed
potential through a safety rated capacitor to provide a low impedance path for
currents induced in the EMI shield. The magnetic structure is particularly useful
as an isolation transformer in an isolated power supply.