Antec Phantom 350: Super-efficient Fanless PSU

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As with several other fanless PSU designs, the Phantom's casing is made of extruded finned aluminum; the case is an external heatsink for the hot components inside. Heat is conducted to the casing, which then transfers the heat into the PC case for convection cooling into the outside air. There is also some radiation of the heat to the air in the PC case.

The entire casing acts as a heatsink. Note grill; there is a similar grill on the other side.

The other side looks identical.

In a long phone conversation, Mr. Han Liu, Antec's Product Development Manager, identified the Phantom design team's primary concerns. His comments are summarized here:

"High Efficiency: Efficiency is important for all PSUs, but especially for a fanless one, because it determines how much heat the PSU has to dissipate. The higher the efficiency, the less heat generated. Antec engineers succeeded in making the Phantom a truly high efficiency PSU that has no equal at this time. Part of its high efficiency can be attributed to the use of a Full Wave rectifier instead of the commonly used half-wave rectifier circuit. (NOTE: For an introduction to the differences between full-wave and half-wave rectifier circuits, please check this source: Rectifier circuits in All About Circuits.)

"Truly Effective Passive Cooling: While previous fanless ATX PSU designs have done a decent job of transferring the heat from the internal heatsinks to the external casing by conduction, many of the large components such as capacitors, coils and transformers are left with little or no cooling. This is because existing fanless PSUs are simple adaptations of fan-cooled PSUs in which such components were cooled by the airflow of the fan. Electrolytic capacitor, in particular, are adversely affected by heat and dry up over time, losing their effectiveness.

"In the Phantom, it is assumed that there is little or no airflow through the PSU. Every hot component is set up to have a direct heat conduction path to the internal heatsinks and/or the outer casing heatsinks. This means that even without direct airflow across those components, they have effective cooling by direct conduction. This thorough design ensures component longevity, which is why Antec can offer a 3-year warranty on the Phantom."

The photos below show some of the details for improved component cooling in the Phantom 350.

Back panel.

Back panel with grill removed.

In the photo directly above, the large coil (inductor) on the right is bonded to a vertical aluminum piece that acts as a heatsink path. It is also connected through a thermal interface (TI) pad to the main heatsink next to it. That heatsink is attached along its entire length to the external casing with a TI pad. The central yellow transformer is similarly attached to the outer casing, as is a second coil to its right.

Inside panel removed.

The photo above shows the other side. The capacitor on the right has a TI pad between its top and the outer casing, and also is pressed up against the HS next to it. In the heatsink next to the bunched wires, an inductor embedded within with a TI pad along its curved perimeter.

(Note: There are no more photos of the interior. Neither the top nor the bottom panel could be removed easily, so rather than force them and break something, those panels remained in place.)

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