Cooler Master Silent Pro M 850 W Power Supply Review

Secondary Analysis

This power supply uses ten Schottky rectifiers on its secondary. 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. Just as an exercise, we can assume a typical duty cycle of 30%.

For the +12 V output six SBR40U60CT Schottky rectifiers are used, each one supporting up to 40 A (20 A per diode at 100° C, 0.60 V maximum voltage drop). Two of them are used for the direct rectification and four are used for the “freewheeling” portion (i.e., discharge the coil). For our math we should consider the portion with the lower current limit, which is the direct rectification one. This gives us a maximum theoretical current of 114 A or 1,371 W for the +12 V output.

The +5 V output uses two SBR30U30CT Schottky rectifiers connected in parallel, each one supporting up to 30 A (15 A per diode at 140° C, maximum voltage drop of 0.54 V). This gives a maximum theoretical current of 43 A or 214 W for the +5 V output.

The +3.3 V output uses another two SBR30U30CT Schottky rectifiers connected in parallel, giving a maximum theoretical current of 43 A or 141 W for the +3.3 V output.

Figure 13: Rectifiers.

This power supply uses a PS224 monitoring integrated circuit, which supports over voltage (OVP), under voltage (UVP) and over current (OCP) protections. Any other protection this unit may have is implemented outside this integrated circuit. On Silent Pro M 850 W we could see two thermal sensors, meaning that this power supply really implements over temperature protection (OTP).

Figure 14: Monitoring circuit.

Electrolytic capacitors from the secondary are also Japanese, from Chemi-Con and labeled at 105° C.