1. A power supply apparatus comprising a power supply module including:
a wind tunnel structure including two power supply substrates with different voltage levels and insulation members forming
two faces of the wind tunnel structure other than faces formed by the power supply substrates, each of the power supply substrates
having a cooling unit mounted on only one of surfaces thereof, the power supply substrates being opposed with the cooling
units adjacent to each other; and
another wind tunnel arranged in a downstream of the wind tunnel structure,
wherein the two power supply substrates are electrically connected to each other via a transformer and a capacitor arranged
in the other wind tunnel.