A Look Inside

The first hint for a high Quality PSU can be seen when taking a first look at it. There is a nice design and high quality case.
Seasonic decided to go for a Sanyo Denki San Ace Fan, which is absolute high end and not often seen in standard PC PSUs. Right at the Input there is a YO15T1 (250V, 15A, CX = 0.1uF, CY= 3300pF*2, Commom Mode (CM choke) = 2*0.3uH) from Yunpen Electronic. At the PCB the transient filtering stage continues with two X, four Y, a CM amd DM choke and four MOV (Metal-Oxid-Varistor). Aditionally there is a NTC Tremistor for inrush curent limitation. A mechanical relais shorts the NTC Termistor for normal operation. The transient filtering stage is well done. We have not seen many PSUs with such an extensive input filtering.

Two GBJ 2506 (25A) are used for rectification. The PFC Booster consists of two IPW60R099CP Mosfets (650V, 0.1Ohm, 31A) and one C3D101060 (600V, 10A, Qc 25nC) SiC Schottky Diode. The APFC is controled by a NCP1654 (54B65) from ON Semiconductor. The NCP1654 has a gate driver performance of 1.5A. This PSU has three APFC capacitors from Nippon Chemi-Con (KMR series; 330uF, 420V, 105C each). Four 60R160C6 (650V, 0.16Ohm, 23.8 A) Mosfets are used on the primary side of the LLC resonance concerter. The LLC resonance converter is controled by a CM6901. The primary side of this PSU is rock solid. Especially the costly transient filtering stage and the high end japanese Nippon Chemi-Con Capacitors are excellent.




On the secundary side eight BSC018N04LS (40V, 1.8mOhm, 100A) Mosfets do the 12V rectification. Those Mosfets are high quality. However the design is basically the same as on Seasonic's X-Series PSU's with lower wattage rating. It seems to us, that the design has been developed for a PSU in the 850W area is now being upscaled, mainly by the use of better components. In our view this design is to close to the limit of a hardware breakdown. Especially the area between the transformer connection and the first Mosfet is weak. Seasonic did also not strengthen this area with an additional copper plate. This has the issue of a relatively high electrical and thermal resistance. This results in a high temperature of the Mosfets (especially the one closest to the transformer) at high loads. The Mosfets are additionaly cooled with a thermal pad, that has been connected to the Case, which also gets very warm under high load at the area of the Mosfets. In this PSU the +12V is the middle connection and also phisicaly in the middle, the Mosfets are switching the ground.



We are also not so happy with the 12V distribution after the rectification. The connection to the front PCB with the 3.3 and 5V converters and the connectors is relatively weak. A PS232 is used for the surveillance of the four 12V rails. Those 4 rails are generated with four coils. There is even a fifth coil for the 3.3 and 5V converter supply. What we highly like to see is that Seasonic makes heavy use of high end japanese Nippon Chemi-Con copacitors on the secondary side. In fact all capacitors we see are from Nippon Chemi-Con with a 105°C rating. Extremely high end. Thank you Seasonic!

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Page 1 - Introduction

Page 2 - Preview

Page 3 - Delivery / Specs

Page 4 - A Look Inside

Page 5 - Input/Output Power and Efficiency

Page 6 - Result Analysis and Discussion

Page 7 - Conclusion

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