Corsair VX450W Power Supply Review

Primary Analysis

We were very curious to check what components were chosen for the power section of this power supply and a
lso how they were set together, i.e., the design used. We were willing to see if the components could really deliver the power announced by Corsair.

From all the specs provided on the databook of each component, we are more interested on the maximum continuous current parameter, given in ampères or amps for short. To find the maximum theoretical power capacity of the component in watts we need just to use the formula P = V x I, where P is power in watts, V is the voltage in volts and I is the current in ampères.

We also need to know under which temperature the component manufacturer measured the component maximum current (this piece of information is also found on the component databook). The higher the temperature, the lower current semiconductors can deliver. Currents given at temperatures lower than 50° C are no good, as temperatures below that don’t reflect the power supply real working conditions.

Keep in mind that this doesn’t mean that the power supply will deliver the maximum current rated for each component as the maximum power the power supply can deliver depends on other components used – like the transformer, coils, the PCB layout, the wire gauge and even the width of the printed circuit board traces – not only on the specs of the main components we are going to analyze.

For a better understanding of what we are talking here, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one GBU806 rectifying bridge in its primary stage, which can deliver up to 8 A (rated at 100° C). This bridge is attached to the same heatsink where the switching transistors are located. This is more than adequate rating for a 450 W power supply. The reason why is that at 115 V this unit would be able to pull up to 920 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 736 W without burning this component. Of course we are only talking about this component and the real limit will depend on all other components from the power supply.

On the active PFC circuit two FQH18N50V2 power MOSFET transistors are used, each one capable of handling up to 20 A at 25° C or 12.7 A at 100° C in continuous mode, or up to 80 A at 25° C in pulse mode. These transistors are located on a separated heatsink, together with the active PFC diode.

Figure 8: Active PFC transistors and diode.

On the switching section this power supply uses another two FQH18N50V2 power MOSFET transistors in two-transistor forward configuration. As mentioned these transistors are capable of handling up to 20 A at 25° C or 12.7 A at 100° C in continuous mode, or up to 80 A at 25° C in pulse mode each and are located on the same heatsink as the rectifying bridge.

Figure 9: Rectifying bridge and switching transistors.

The primary section is controlled by a CM6800 integrated circuit, which is a very popular active PFC and PWM controller combo. It is located on a small printed circuit board attached to the main board.

Figure 10: PFC and PWM controller combo.