Contents
- 1Introduction
- 1.1Packaging and accesories
- 2Connectors & cabling
- 2.1Casing & cooling
- 3Input filtering
- 4Primary side
- 4.1+5 V stand-by rail
- 5Secondary side
- 5.1Build quality
- 6Load testing
- 6.1Loading +5 V SB
- 6.2Combined loading
- 6.3Combined loading ripple
- 6.4Crossloading, overloading
- 6.5Crossloading, overloading ripple
- 7Conclusion and evaluation
- 7.1Thanks
Secondary side
The S12G and similar Seasonic units have only single positive rail winding on the main transformer, the +12 V. The negative rail (with much smaller winding) is −12 V. This +12 V rail is actively rectified by two NXP PSMN2R6-40YS (100 A at 100 °C/651 A pulsed at 25 °C and 40 V, RDS(On) 3.7 mΩ at 25 A and 100 °C) transistors in LFPAK package, together with two SBR10U45D1 rectifiers (semi-synchronnous rectification). Heat from this silicon is conducted away using a piece of metal soldered in the board which has aluminium heatsink mounted to it. Aluminium on the board with DC-DC modules covers Anpec APW7159 two-channel controller, which consists of 3+4 transistors Infineon IPD060N03L G (50/350 A at 25 °C and 30 V, RDS(On) 6 mΩ at 30 A and 25 °C). The +12 V rail is then separated into two rails with separate over-current protection, monitored by Silicon Touch Technology PS223 monitor IC, placed on another small daughterboard. It also monitors under/overvoltage and turns the PSU on/provides the Power Good signal.
Five Enesol Enecap RL 470 μF/16 V polymer capacitors are used for filtration of the +12 V rail before it is split into two rails, then there are two KZH 3900/16 for each output rail, behind their Pi coils. One rail is for PCIe connectors, the other one for everything else. Two other polymers are on the input of each DC-DC module, on their output is KZE 3300/10 and 2200/16 for each rail (+3.3 and +5 V). The −12 V rail has KY 1000/16 and KZE 2200/16. There is also a Rubycon ZLH 68/25 for filtration of the feed for fan (from transistor speed controller). The Enesol RL polymers have specified lifetime of 3000 hours at 105 °C, their true manufacturer is Taiwanese Matsuki Precision Ceramic Corporation. The Enesol was found as another daugther company/brand connected with new Korean factory back in 2004, later (2006) they fused again back into Matsuki.
Build quality
As usual I will focus on the overall build quality and other things like electrical safety here as the quality of the components used was already discussed before. Both thermistor and varistor here are insulated with additional layer of heatshrink, there are also multiple pieces of insulation foil between components; the insulation is OK for high-end unit. Higher quality fiberglass PCB is used, primary and secondary side separation is good. SMD components in the stand-by rail circuitry are covered with glue as protection from moisture.
I somewhat do not understand placing the differential choke right next to the main transformer, I wonder if such high overall ripple is caused by this as the choke must radiate interference. There is also some mess on the soldering of this choke, both soldering flux and solder residue, I found approx. four tiny solder balls. I have seen worse from Seasonic, this soldering is quite OK (it even seems there are no manual repairs) so lets take off two points here for the solder balls. As usual, components are covered in silicone glue. I hate this stuff!
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