Aerocool E85M-550 Power Supply Review
Secondary Analysis
Contents
This power supply has four Schottky rectifiers attached to the secondary heatsink.
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%.
The +12 V output is generated using two SBR30A50CT Schottky rectifiers connected in parallel, each one having a current limit of 30 A (15 A per internal diode at 110° C, 0.55 V maximum voltage drop). This gives us a maximum theoretical current of 43 A or 514 W for the +12 V output. The V12XT-600 uses two 40 A rectifiers here (57 A/686 W maximum theoretical output).
The +5 V output is generated using one STPS30L45CT Schottky rectifier, which is able to handle up to 30 A (15 A per internal diode at 110° C, 0.74 V maximum voltage drop). This gives us a maximum theoretical current of 21 A or 107 W for the +5 V output. The V12XT-600 uses a different component here, but with the same specs.
The +3.3 V output is generated using another STPS30L45CT Schottky rectifier. This gives us a maximum theoretical current of 21 A or 107 W for the +3.3 V output. The V12XT-600 uses two 30 A rectifiers here (43 A/141 W maximum theoretical limit).
Of course these are all theoretical figures. The real current limits will depend on other components, especially on the coil used.
Figure 14: The +5 V and one of the +12 V rectifiers
Figure 15: The other +12 V and the +3.3 V rectifiers
The outputs are monitored by a WT7525 integrated circuit. This circuit supports over voltage (OVP), under voltage (UVP), and over current (OCP) protections. This circuit offers four over current protection channels (one for +3.3 V, one for +5 V, and two for +12 V), correctly matching the number of +12 V rails advertised by the manufacturer (two).
Figure 16: Monitoring circuit
The electrolytic capacitors available in the secondary are from Teapo and labeled at 105° C.