Secondary Analysis

This power supply uses four Schottky rectifiers on its secondary, however they are connected on a way that is different from other power supplies.

Nowadays on power supplies with four rectifier packs we usually have two of them connected in parallel rectifying the +12 V line, one rectifying the +5 V and another rectifying the +3.3 V line. This reflects the current usage of power supply, where most of the power is pulled from the +12 V outputs. In the past most of the power was concentrated on the +5 V outputs.

On this power supply, however, the two rectifiers that are connected in parallel are in charge of the +5 V outputs and they are used, at the same time, for helping the rectification on the +12 V line. This is the first time we’ve seen such exotic configuration. To help you to understand this configuration, we have drawn a simple schematics of the secondary from this power supply on Figure 13.

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Figure 13: The secondary.

All four Schottky rectifiers are the same: DF40S4. Each pack can handle up to 40 A at 106º C. This gives a maximum theoretical power of 132 W for the +3.3 V output, 400 W for the +5 V output and 480 W for the +12 V output. The maximum current each line can really deliver will depend on other components, especially the transformer, the coil, the capacitor and the wire gauge used.

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Figure 14: Secondary rectifiers.

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Figure 15: Secondary rectifier and -12 V voltage regulator.

This power supply uses a thermal sensor on its secondary heatsink (see Figure 16; to take this picture we removed the secondary heatsink), which is used to control the fan speed according to the power supply internal temperature and also to shut it down in the case of an overheating situation.

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Figure 16: Thermal sensor.

This power supply uses a PS223 monitoring integrated circuit (see it on Figure 16), which is in charge of the power supply protections, like OCP (over current protection). This IC also provides over voltage protection (OVP), under voltage protection (UVP) and over temperature protection (OTP), but not over power protection (OPP).

The active PFC capacitor is Japanese from Chemi-Con and rated at 85º C, while the electrolytic capacitors from the secondary are rated at 105º C.

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