SilverStone Element ST50EF-Plus 500 W Power Supply Review
Secondary Analysis
Contents
This power supply uses three 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%.
The +12 V output is produced by one STPS60L45CW Schottky rectifier, which has a maximum current limit of 60 A (30 A per diode at 135° C, 0.50 V voltage drop). This gives us a maximum theoretical current of 43 A or 514 W for the +12 V output.
The +5 V output is produced by another STPS60L45CW Schottky rectifier, giving us a maximum theoretical power of 214 W for this line.
The +3.3 V output is produced by one 40CPQ060 Schottky rectifier, which supports a maximum current of 40 A (20 A per diode at 120° C, 0.49 V voltage drop), giving us a maximum theoretical current of 29 A or 94 W for the +3.3 V output.
What is unique about this power supply is the use of a MOSFET transistor to rectify the -12 V output (it is used an IRF2807 transistor, which is capable of handling up to 58 A at 100° C in continuous mode).
Figure 12: +5 V and +3.3 V rectifiers and -12 V transistor.
Figure 13: +12 V rectifier.
This power supply uses a WT7517 monitoring integrated circuit, which is in charge of the power supply protections. It supports over voltage (OVP), under voltage (UVP), over current (OCP) and over temperature (OTP) protections. This power supply really implemented the over temperature protection, which we could confirm by the presence of two thermal sensors, one for controlling the fan and one for this circuit. In most power supplies the monitoring integrated circuit supports over temperature protection but this protection isn’t activated, as the thermal sensor necessary for this protection to work is not installed.
Figure 14: Monitoring integrated circuit.
Electrolytic capacitors from the secondary are from Teapo and Su’scon and labeled at 105° C.