PC Power & Cooling Silencer Mk II 500 W Power Supply Review

Secondary Analysis

As explained in the Introduction, the 500 W model uses a different design on the secondary compared to the more powerful members in the Silencer Mk II family: it uses a traditional design using Schottky rectifiers, while the other models use a synchronous design (meaning that the Schottky rectifiers were replaced by MOSFET transistors in order to increase efficiency) with DC-DC converters (the +5 V and +3.3 V outputs are generated by two small power supplies attached to the +12 V output).

The maximum theoretical current each 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. As an exercise, we can assume a duty cycle of 30%.

The +12 V output uses two S30D60C Schottky rectifiers, each one supporting up to 30 A (15 A per internal diode at 125° C, 0.70 V maximum voltage drop), giving us a maximum theoretical current of 43 A or 514 W for the +12 V output.

The +5 V output uses two S30D45C Schottky rectifiers, giving us a maximum theoretical current of 43 A or 214 W for the +5 V output.

The +3.3 V output uses another two S30D45C Schottky rectifiers, giving us a maximum theoretical current of 43 A or 141 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.

Figure 14: +5VSB, +3.3 V, +5 V and +12 V rectifiers

This power supply uses a PS224 monitoring integrated circuit, which supports over voltage (OVP), under voltage (UVP) and over current (OCP) protections. The over current protection circuit available in this integrated circuit has four channels, one for +3.3 V, one for +5 V, and two for +12 V. However, in this power supply only one +12 V OCP channel is used, as it has a single-rail design.

Figure 15: Monitoring circuit

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