BFG ES-800 Power Supply Review

Secondary Analysis

The design used on the secondary from ES-800 is similar to the one used by some other power supplies we reviewed recently, like Corsair HX850W and Seasonic M12D 750 W. The main transformer is directly connected to a bank of eight SBR4045CT Schottky Rectifiers in charge of producing the +12 V output. Each one of these rectifiers can deliver up to 40 A (20 A per internal diode at 110° C with a typical voltage drop of 0.47 V. We are now indicating the voltage drop, as this spec has direct impact on efficiency. Voltage drop is a small amount of voltage that is wasted by the diode when it is conducted. The lower this number, the lower the waste and thus the higher efficiency is. This bank has a maximum theoretical current of 228.6 A (20 A x 8 / 0.70). This theoretical limit is for the whole secondary, as the +5 V and +3.3 V are produced from +12 V.

Figure 14: Rectifiers.

The +5 V and +3.3 V outputs are produced from the +12 V output using two NTB125N2RG MOSFET transistors each. Each MOSFET is capable of delivering up to 95 A at 25° C in continuous mode and a maximum RDS(on) of only 0.0062 ohms (6.2 mΩ), promising to provide high efficiency.

Figure 15: Transistors used for the +5 V and +3.3 V outputs.

This power supply uses a PS232S monitoring integrated circuit, which is in charge of the power supply protections. Unfortunately there is no information about this circuit on the manufacturer’s website.

Figure 16: Monitoring circuit.

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