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.
