Articles: Cases/PSU

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It is easy to identify the real maker of this PSU by its internal design. It is the well-known and respectable Seasonic. You can sometimes learn the manufacturer by the UL certificate number even without opening the PSU case but Corsair has obtained its own certificates.

The internal component layout of the VX450W represents a typical modern power supply. Its load-bearing semiconductor components are distributed among three heatsinks (from left to right): a heatsink with the transistors and diodes of active power factor correction (PFC), a heatsink with switching transistors, and a heatsink with output diode packs. The first two heatsinks are rather slim (2mm) black-painted aluminum bars with turned out ribs. The third heatsink consists of two such bars fastened together. You shouldn’t be surprised at this simplicity. Too massive and branchy heatsinks may even worsen the efficiency of cooling by producing more resistance to the airflow and thus reducing the speed of the latter. I have seen practical examples of this point quite a lot of times in my practice.

The PSU follows a classic circuit design with joint voltage regulation. There are two toroidal chokes next to the output cables, one of which regulates the +3.3V voltage while the other, the +5V and +12V voltages both together. It means that the voltage in the +5V rail depends on the load on the +12V rail and vice versa.

There are two chokes and noise filter’s capacitors near the exterior panel of the PSU. In the left part of the case, in between the heatsinks, there is an active PFC choke. You can see it clearly in the first photo of the PSU’s interior. The small additional card located nearby carries a chip that combines PFC and main regulator controllers. I couldn’t discern its marking as the chip was almost pressed to one of the heatsinks. The standby voltage regulator is based on an Infineon ICE2A0565Z.

KZE series electrolytic capacitors from United Chemi-Com are installed at the PSU’s output. They are rated for a temperature up to 105°C and are specifically designed for switching power supplies, besides other applications.

There is one 400V/330µF capacitor at the PSU’s input. Many reviewers note with pleasure that it is rated for a temperature of 105°C as well, but the temperature range is actually unimportant for a high-voltage capacitor and does not affect the PSU’s service life. This capacitor just doesn’t get too hot at work. Instead, I am rather surprised at its operating voltage. When the PSU is turned on, this capacitor’s voltage is 380V which is only 20 volts below the permissible maximum.

The transistors and diodes are installed in a curious way. They are all designed in compact TO-220 packages and are glued with thermal paste to aluminum bars that are somewhat larger in diameter than the package. The bars are screwed up to the heatsink via an insulating pad. This solution must be due to the low thermal conductivity of the insulating pads: the developer increased the heat dissipation area by using those aluminum bars.

The PSU is cooled with a 120x120x25mm fan (Adda AD1212MB-A71GL, 2050rpm). It uses a 2-pin connection.

About one fourth of the fan is covered with a piece of translucent celluloid film in order to achieve optimal airflows within the PSU housing. The latter has vent holes in the exterior panel only. If the fan were open fully, there would a high-pressure zone with slow airflow near the blank back panel whereas cooling efficiency depends directly on the speed of the air. When the front part of the fan is covered with the film as in this PSU, the airflow goes only into the back part of the PSU, then along the heatsinks, and out through the perforated front.

Having a total output power of 450W, the PSU can provide up to 396W (33A) across its +12V power rail. This rail is not divided into “virtual” multiple outputs, so you won’t have any problems connecting a couple of graphics cards, for example.

I want to remind you that the “virtual” division of the +12V rail is implemented for the sake of compliance with the safety regulations according to which the output power on any of user-accessible connectors of a PSU must not be higher than 240VA. When the load capacity of the +12V rail grew up beyond that mark, the developers began to install individual current limiters (set at about 18A) on the different output cables of the PSU. As a result, you could get the full output power of the PSU from all its cables combined, but only 12*18=216W from each cable taken individually. This solution can provoke some problems, for example when the PSU has two +12V output lines one of which powers the CPU and the other, the rest of the components. If the power consumption of the “rest of the components” is higher than 216W (this may happen if you have two graphics cards in SLI mode), the PSU will shut down due to the overload on the specific +12V line although it still has some reserve of wattage.

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