Secondary Analysis
Contents
Even though this power supply has two transformers, the output of all +12 V rectifiers are connected together.
This power supply uses eight Schottky power rectifiers on its secondary, four 63CPQ100 (60 A at 153° C, 30 A per internal diode) and four 40CTQ045 (40 A at 116° C, 20 A per internal diode).
The +12 V output uses all the four 63CPQ100 Schottky rectifiers. Two of them are connected to one transformer and the other two are connected to the other transformer, however the outputs of all four rectifiers are connected together. The maximum theoretical current the +12 V line can deliver is given by the formula I / (1 – D), where D is the duty cycle used and I is the maximum current supported by the rectifying diode (which in this case is made by four 30 A diodes, two of them connected, in parallel, to the first transformer, and another two connected, in parallel, to the second transformer). Just as an exercise, we can assume a typical duty cycle of 30%. This would give us a maximum theoretical current of 171 A or 2,057 W for the +12 V output. The maximum current this line can really deliver will depend on other components, in particular the coil used. This output is clearly overspec’ed.
For the +5 V output two 40CTQ045 are used. The maximum theoretical current the +5 V line can deliver is given by the formula I / (1 – D), where D is the duty cycle used and I is the maximum current supported by the rectifying diode (which in this case is made by two 20 A diodes in parallel). Just as an exercise, we can assume a typical duty cycle of 30%. This would give us a maximum theoretical current of 57 A or 286 W for the +5 V output. The maximum current this line can really deliver will depend on other components, in particular the coil used.
The +3.3 V output also uses two 40CTQ045 Schottky rectifiers, connected to a dedicated transformer output, which is terrific. On the vast majority of power supplies even when the +3.3 V output has its own rectifiers, they are connected to the same transformer output as the +5 V line, so the transformer limits the maximum current (and thus power) the +5 V and +3.3 V lines can deliver together (a concept called “combined power”). Using the same math the +3.3 V output would be capable of delivering up to 189 W. Like we said before, the other components used on the power supply will limit the maximum current and power this output can actually deliver.
On the pictures below you can see the rectifiers used on this powe
r supply secondary.
Figure 24: Rectifiers used on the secondary.
Figure 25: Rectifiers used on the secondary.
In Figure 26, you can see the thermal sensor from this power supply, in charge of changing the speed of the fans according to the power supply internal temperature. Usually this component is found attached directly to the secondary heatsink or right below it, but on this power supply it is located inside the +12 V coil.
Figure 26: This power supply thermal sensor is located inside the +12 V coil.
