We were very curious to check what components were chosen for the power section of this power supply and also 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 50º 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 and the wire gauge – 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 GBJ1506 rectifying bridge on its primary stage, which can deliver up to 15 A (rated at 100º C). This component is clearly overspec'ed: at 115 V this unit would be able to pull up to 1,725 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 1,380 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.
Four power MOSFET transistors are used on this power supply primary, two on the active PFC circuit and two on the switching section. On the active PFC circuit two 20N60C3 are used. These transistors have a maximum rated current of 45 A each at 25º C or 20 A at 110º C in continuous mode or up to 300 A at 25º C in pulsating mode.
On the switching section two FQPF18N50V2 power MOSFET transistors in two-transistor forward switcher configuration are used, and each one has a maximum rated current of 72 A in pulsating mode, which is the mode used, as the PWM circuit feeds these transistors with a square waveform. In continuous mode they can deliver up to 18 A @ 25º C or up to 12.1 A @ 100º C.
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Figure 12: MOSFET transistors used on the primary.
For a better understanding on the relationship between these transistors, we drew a simplified diagram of this section of HX620W power supply, see Figure 13.
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Figure 13: Simplified diagram of this power supply showing the location of its four MOSFET transistors.
A very interesting feature from this power supply is that its fuse is inside a fireproof rubber protection. So this protection will prevent the spark produced on the minute the fuse is blown from setting the power supply on fire.
The primary section is controlled by a UCC28515 integrated circuit, which is an active PFC and PWM controller combo. It is located on a small printed circuit board shown on Figure 14.
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Figure 14: Active PFC and PWM controller integrated circuit.
