Rosewill Tachyon 750 W Power Supply Review

Secondary Analysis

As one would expect in a high-efficiency power supply, the Rosewill Tachyon 750 W uses a synchronous design, where the Schottky rectifiers are replaced with MOSFETs. Also, the reviewed product uses a DC-DC design in its secondary. This means that the power supply is basically a +12 V unit, with the +5 V and +3.3 V outputs produced by two smaller power supplies connected to the main +12 V rail. Both designs are used to increase efficiency.

The +12 V output uses four IPP041N04N G MOSFETs, each one supporting up to 80 A at 100° C in continuous mode and up to 400 A at 25° C in pulse mode, with a maximum RDS(on) of 4.1 mΩ. Strangely, the AZZA Platinum 750 W uses different transistors here (IPP023N04N G, supporting up to 90 A at 100° C in continuous mode and up to 400 A at 25° C in pulse mode, with a maximum resistance of only 2.3 mΩ).   

Figure 15: The +12 V transistors

As explained, the +5 V and +3.3 V outputs are produced by two DC-DC converters, which are situated on a single printed circuit board located in the secondary section of the power supply. Each converter is controlled by one NCP1587A integrated circuit and uses two IPD060N03L MOSFETS, each supporting up to 50 A at 100° in continuous mode and up to 350 A at 25° C in pulse mode, with a maximum RDS(on) of 6 mΩ. On the AZZA Platinum 750 W, each output uses four IPD040N03L MOSFETs, each supporting up to 76 A at 100° C in continuous mode and up to 400 A at 25° C in pulse mode, with a maximum RDS(on) of 4 mΩ.

Figure 16: The DC-DC converters

Figure 17: The DC-DC converters

We didn’t see an integrated circuit for monitoring the power supply outputs. Since the Power Good wire and sensors were connected to the small printed circuit board where the resonant controller was attached, our best guess is that the enigmatic SF29601 controller, with the aid of four operational amplifiers provided by an LM324 integrated circuit, did the trick.  

The elect
rolytic capacitors available in the secondary are also Japanese, from Chemi-Con, and labeled at 105° C, as usual.

Figure 18: Capacitors