PC Power & Cooling Silencer 760 W Power Supply Review

Secondary Analysis

This power supply uses a DC-DC design in its secondary, meaning that this unit is basically a +12 V power supply, with the +5 V and +3.3 V outputs being generated by two smaller power supplies attached to the +12 V output.

The +12 V output is rectified by eight SBR40S45CT Schottky rectifiers, each one supporting up to 40 A (20 A per internal diode at 110° C, 0.55 V maximum voltage drop). Three are used for the direct rectification and five are used on the “freewheeling” part of the rectification. This gives a maximum theoretical current of 171 A or 2,057 W for the +12 V rail.

Figure 14: Five of the eight +12 V rectifiers

As already explained, the +5 V and +3.3 V outputs are obtained through two smaller switch-mode power supplies connected to the +12 V output. They are both located on the same daughterboard, which makes use of two APW7073 PWM controllers and seven APM2556N MOSFETs, with a maximum RDS(on) of only 7.2 mΩ.

Figure 15: The DC-DC converter

Figure 16: The DC-DC converter

The secondary is monitored by a PS223 integrated circuit. This chip supports OCP (over current protection), over voltage protection (OVP), under voltage protection (UVP) and over temperature protection (OTP). This circuit has four OCP channels (+3.3 V, +5 V and two +12 V), but the manufacturer decided to use only one for the +12 V output, making this power supply a single-rail unit.

Figure 17: Monitoring circuit

Electrolytic capacitors found in the secondary are also Japanese, from Chemi-Con.