In Win GreenMe 750 W Power Supply Review

Secondary Analysis

The In Win GreenMe 750 W uses a DC-DC design in its secondary. This means that the power supply is basically a +12 V unit, with the +5 V and +3.3 V outputs produced by two smaller power supplies connected to the main +12 V rail. This design is used to increase efficiency.

The maximum theoretical current that 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. As an exercise, we can assume a duty cycle of 30 percent.

The +12 V output uses four PFR40L60PT Schottky rectifiers, each supporting up to 40 A (20 A per internal diode at 110° C with a 0.65 V maximum voltage drop). This gives us a maximum theoretical current of 114 A or 1,371 W for the +12 V output. However, keep in mind that the +5 V and the +3.3 V outputs are generated from the +12 V output.

Figure 13: Two of the four +12 V rectifiers and the +5VSB rectifier

As explained, the +5 V and +3.3 V outputs are produced by two DC-DC converters. Each is located on a small daughterboard soldered to the main printed circuit board. In Figures 14 and 15, you can see the physical aspect of one of these converters. Each is controlled by a uP3872B integrated circuit, using two QM3004D (marked “M3004D”) and two QM3016D (marked “M3016D”) MOSFETs. Each QM3004D supports up to 55 A at 25° C or 40 A at 100° C in continuous mode or up to 110 A at 25° C in pulse mode, with an RDS(on) of 8.5 mΩ, while each QM3016D supports up to 96 A at 25° C or 68 A at 100° C in continuous mode or up to 192 A at 25° C in pulse mode, with an RDS(on) of 4 mΩ.

Figure 14: One of the DC-DC converters

Figure 15: One of the DC-DC converters

This power supply uses a WT7579 monitoring integrated circuit. This chip supports over voltage (OVP), under voltage (UVP), over current (OCP), and over temperature (OTP) protections. There are four +12 V over current protection (OCP) channels, matching the number of +12 V rails advertised by the manufacturer.

Figure 16: Monitoring circuit

The electrolytic capacitors that filter the outputs are from Teapo and Samxon and labeled at 105° C, as usual.