FSP Zen (FSP300-60GNF)

The FSP Zen looks quite strange even when compared with other fanless PSUs which usually have large protruding heatsinks. The Zen is a neat box without any jutting details at all.

Most of the case is covered with small-meshed vent grids (it would be better to have a larger mesh from the technical point of view, I should note). The power supply is only cooled by means of convection: warm air from the system case comes in through the grid in the case of the power supply and then goes out through its rear panel.

You can’t see anything inside after you’ve removed the cover – the components of the PSU are hidden under the three large heatsinks. Note that they differ from heatsinks in fan-cooled PSUs: instead of small bars with thin and densely placed fins we have massive aluminum blocks with thick fins here.

The top parts of the heatsinks can be removed (all junctions are carefully covered with thermal paste) to reveal us the internal design of the PSU:

The power semiconductor elements are distributed among three heatsinks rather than between two, as usual. The PSU’s high-voltage elements (the active PFC device and the transistors of the main and standby regulators) reside on the first two heatsinks; the third heatsink carries the diode packs of the output low-voltage rectifiers. A separate perforated heatsink positioned perpendicularly to the others cools the diode bridge on the PSU output (this bridge doesn’t heat up much, so there’s no need to add anything to the top of this heatsink).

The 270µF 450V smoothing capacitor that stands after the PFC device is rated for a temperature of 105°C, while ordinary PSUs usually have 85°C capacitors on their output. This is a reasonable solution. The capacitor itself doesn’t heat up much, of course, but the proximity of a hot heatsink might tell negatively on its service life as there are no strong airflows inside the case. A rather large active PFC coil is located near the capacitor. The choke coils of the line filter can also be seen on the snapshot (between the diode-bridge heatsink and the rear panel of the PSU). The line filter is complete, so I have no complaints about it.