Rosewill Libertas 800 W Power Supply Review

Secondary Analysis

This power supply uses a synchronous design on its secondary, meaning that the Schottky rectifiers were replaced by MOSFET transistors in order to increase efficiency. On top of that, this unit uses a DC-DC design, meaning that this unit is basically a +12 V power supply, with the +5 V and +3.3 V outputs being generated by two small power supplies attached to the +12 V output.

The +12 V output is generated by four IXTP230N075T2 MOSFETs, each one capable of handling up to 75 A at 100° C in continuous mode, with an RDS(on) of only 4.2 mΩ. Two of these transistors are in charge of the direct rectification, while the other two are in charge of the “freewheeling” part of the rectification. A DSB60C45HB Schottky rectifier is used to complement the “freewheeling” part of the rectification.

Figure 14: +12 V transistors

The +5 V and the +3.3 V outputs are generated by two small power supplies found on small daughterboards attached to the +12 V rail. Each of these power supplies is comprised of four ME90N03 MOSFETs (47 A at 70° C, 4.8 mΩ resistance) and one PWM controller (we couldn’t identify as the manufacturer covered this integrated circuit with a black material that was impossible to remove).

Figure 15: The +5 V DC-DC converter

Figure 16: The +5 V DC-DC converter

This power supply uses a PS232S monitoring integrated circuit, which supports over voltage (OVP), under voltage (UVP), and over current (OCP) protections. The over current protection circuit available in this integrated circuit has six channels, one for +3.3 V, one for +5 V, and four for +12 V, but the manufacturer decided to configure this power supply as a single-rail unit.

Figure 17: Monitoring circuit

Electrolytic capacitors in the secondary are from Teapo, labeled at 105° C. Some solid capacitors from CapXon are found as well. The capacitors used on the DC-DC boards are solid, as you can see in Figure 16.