SilverStone ST45SF-G Power Supply Review

Secondary Analysis

As one would expect in a high-efficiency power supply, the SilverStone ST45SF-G 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 two IRLB3034PbF MOSFETs, each one supporting up to 343 A at 25° C or 243 A at 100° C in continuous mode, or up to 1,372 A at 25° C in pulse mode, with a maximum RDS(on) of 1.7 mΩ.

Figure 16: 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 individual printed circuit boards located in the secondary section of the power supply. Each converter is controlled by an APW7073 integrated circuit and uses one CSD86350Q5D MOSFET. This transistor supports up to 40 A at 25° C in continuous mode and up to 120 A at 25° C in pulse mode, with a maximum RDS(on) of 2.7 mΩ.

Figure 17: One of the DC-DC converters

Figure 18: One of the DC-DC converters

The outputs of the power supply are monitored by a PS223 integrated circuit, which supports over voltage (OVP), under voltage (UVP), over current (OCP), and over temperature (OTP) protections. There are two +12 V over current channels, but the manufacturer decided to use only one of them, therefore resulting in this unit having a single +12 V rail configuration.

Figure 19: Monitoring circuit

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

Figure 20: Capacitors