Seasonic X-Series 560 W Power Supply Review

Secondary Analysis

This power supply uses a synchronous design in 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 IPD036N04L MOSFETs, each one capable of handling up to 90 A at 25° C or up to 87 A at 100° C in continuous mode or up to 400 A at 25° C in pulse mode, with an RDS(on) of only 3.6 mΩ. These transistors are soldered directly on the solder side of the printed circuit board, and the power supply housing is used as a heatsink for them. The +5 V and +3.3 V are produced from the +12 V output, but just as an exercise if all power from this unit was pulled exclusively from the +12 V rail, this unit would have a maximum theoretical current of 249 A or 2,983 W. These are the same transistors used in the X-400 Fanless and X-Series 650 W.

Figure 14: +12 V transistors

Usually power supplies that use DC-DC converters in the secondary to generate the +5 V and +3.3 V outputs have two separate printed circuit boards installed in the secondary, one for each output. Like other “X-Series” power supplies from Seasonic, in the X-Series 560 W these converters are installed on the modular cabling printed circuit board.

Figure 15: The DC-DC converter

Figure 16: The DC-DC converter

Both outputs are managed by an APW7159 PWM controller, and each output is generated by four IPD060N03L MOSFETs, each one capable of handling up to 50 A at 100° C in continuous mode, or 350 A at 25° in pulse mode, with an RDS(on) of only 6 mΩ. These are the same components used in the X-400 Fanless, but the X-Series 650 W uses different components here.

In Figure 17, you can see how there are several solid capacitors in the secondary (and the capacitors that aren’t solid are made in Japan, by Chemi-Con), and how Seasonic added some interesting heatsinks connected straight to the printed circuit board.

Figure 17: Heatsinks and solid capacitors

The secondary is monitored by a PS223 integrated circuit. This chip supports OCP (over current protection), over voltage protection (OVP), under voltage protection (UVP) and over t
emperature protection (OTP).

Figure 18: Monitoring circuit