Logisys PS600A12 Power Supply Review

Secondary Analysis

The +12 V output uses one BYW51-200 rectifier, which supports up to 16 A (8 A per internal diode at 156° C, 0.97 V maximum voltage drop), giving us a maximum theoretical current of 16 A or 192 W for the +12 V output. It is important to understand that this rectifier is of the “ultra fast” type, not “Schottky.”

The +5 V output uses one ESAD83-004 (“D83-004”) Schottky rectifier, which supports up to 30 A (15 A per internal diode at 90° C, 0.55 V maximum voltage drop), giving us a maximum theoretical current of 30 A or 150 W for the +5 V output.

The +3.3 V output uses another ESAD83-004 Schottky rectifier, giving us a maximum theoretical current of 30 A or 99 W for the +3.3 V output.

All these numbers are theoretical. The real amount of current/power each output can deliver is limited by other components, especially by the coils used on each output.

Here you can clearly see three things. First, the +5 V output is “stronger” than the +12 V output, which is a typical scenario for power supplies projected more than 10 years ago. Nowadays the most current/power is pulled from the +12 V output (because there is where the CPU and the video cards are connected to) and, therefore, this output should be the “strongest.” Second, the +12 V rectifier is an “ultra fast” model, not a “Schottky” model, also showing how obsolete this unit it. And, third, if we add up all the maximum theoretical powers we get 441 W, so it is simply impossible for this power supply to be a 600 W model.

Figure 13: +3.3 V, +12 V and +5 V rectifiers

The protections of this unit are built discretely using an LM339 voltage comparator. We couldn’t figure out which protections are really implemented.

Figure 14: Voltage comparator