Seasonic Prime Fanless 700 W Review 24

Seasonic Prime Fanless 700 W Review

Voltage Regulation Stability & Ripple »

Component Analysis

Before reading this page, we strongly suggest looking at this article, which will help you better understand the insides of a PSU.

Seasonic Prime Fanless TX-700 Parts Description
General Data
Manufacturer (OEM)Seasonic
PCB TypeDouble-Sided
Primary Side
Transient Filter5x Y caps, 3x X caps, 2x CM chokes, 1x MOV, 1x Champion CM02X (Discharge IC)
Bridge Rectifier(s)2x Vishay LVB2560 (600 V, 25 A @ 105 °C)
Inrush Current ProtectionNTC Thermistor (MF72-5D20L) (5 ohm) & Relay
APFC MOSFETs2x Infineon IPP60R099C7 (600 V, 14 A @ 100 °C, Rds (on): 0.099 ohm)
APFC Boost Diode1x CREE C3D06060A (600 V, 6 A @ 154 °C)
Bulk Cap(s)2x Nippon Chemi-Con (400 V, 470 uF each or 940 uF combined, 2,000 h @ 105 °C, KMR)
Main Switchers4x Infineon IPP50R140CP (550 V, 15 A @ 100 °C, Rds (on): 0.14 ohm)
IC Driver(s)2x Silicon Labs Si8230BD
APFC ControllerOn Semiconductor NCP1654
Switching ControllerChampion CM6901T2X
TopologyPrimary Side: APFC, full-bridge & LLC converter
Secondary Side: synchronous rectification & DC-DC converters
Secondary Side
+12 V MOSFETs8x Infineon BSC014N04LS
(40 V, 125 A @ 100 °C, Rds (on): 1.4 mOhm)
+5 V & +3.3 VDC-DC Converters:
6x Infineon BSC0906NS
(30 V, 40 A @ 100 °C, Rds (on): 4.5 mOhm)
PWM Controllers:
ANPEC APW7159C
Filtering Capacitors

Electrolytic:
1x Nichicon (4–10,000 h @ 105 °C, HE),
1x Nichicon (2–5,000 h @ 105 °C, HD),
1x Nippon Chemi-Con (4–10,000 h @ 105 °C, KΒY),
1x Nippon Chemi-Con (5–6,000 h @ 105 °C, KZH),
1x Rubycon (3 - 6,000 h @ 105 °C, YXG),
1x Nippon Chemi-Con (4–10,000 h @ 105 °C, KY)

Polymer:
14x FPCAP
10x Nippon Chemi-Con

5V to 5VSB ORing SBRs3x MCC MBR1045ULPS SBR (45 V, 10 A)
Supervisor ICWeltrend WT7527V (OCP, OVP, UVP, SCP, and PG)
5VSB Circuit
Rectifier(s)1x Infineon IPA65R1K5CE FET (650 V, 3.3 A @ 100 °C, Rds (on): 1.5 ohm)
1x MCC MBR1045ULPS SBR (45 V, 10 A)
Standby PWM ControllerLeadtrend LD7750R


The PCB is large to increase the space between parts for better airflow. Moreover, there are heatsinks everywhere since there is no active cooling. Even the main transformer is fitted with a heatsink, which is good since it can get quite hot. To offer better load regulation on the minor rails and increase efficiency through lower energy losses on power transfers, the DC-DC converters handling these rails are on the modular PCB. A thick cable is used to feed the VRMs of the minor rails 12 V—a bus bar would have been better.


The transient/EMI filter stages include five Y and three X caps. Two CM chokes and a Champion CM02X discharge IC are also used.


A Metal Oxide Varistor (MOV) handles voltage surges, while an NTC thermistor and relay combination suppresses large inrush currents.


The bridge rectifiers are powerful, able to handle up to 50 A of current, which is way more than what this power supply will require.


The APFC converter uses two Infineon FETs and a CREE boost diode, which I expected to be stronger since all parts for this PSU are over spec. The bulk caps are by Chemi-Con, and their combined total capacity is 940 uF, so the hold-up time will easily exceed 17 ms.


The APFC controller is an On Semiconductor NCP1654. It is on a vertical daughter-board, which looks strange since it is quite small, so it would easily fit on the main PCB. Seasonic probably did this for ease of swappability.


The four main FETs are by Infineon and installed in a full-bridge configuration.


The unit's main transformer has a large heatsink on top of it to help it keep its temperatures low.


This photos shows the unit's resonant controller and resonant tank, parts of the LLC resonant converter.


The FETs regulating the +12 V rail are installed on the solder side of the main PCB. Heatsinks on the other side of the PCB handle their thermal load.


Two DC-DC converters generate the minor rails. They are installed on the modular PCB to be closer to the peripheral and main ATX sockets for lower voltage drops.


Seasonic used topnotch caps since there is no active cooling and their operating temperatures will be higher than typical. Many polymer caps are used, and these are significantly more tolerant to high operating temperatures than electrolytic ones.


The 5VSB circuit uses three MCC ORing diodes to combine current from the 5 V circuit and deliver it to the 5VSB rail.


The standby PWM controller is a Leadtrend LD7750R.


The supervisor IC is a Weltrend WT7527V, which provides all essential protection features but OTP. The latter is implemented through another circuit.


Several polymer caps are installed on the face of the modular PCB. The supervisor IC and TPS54231 buck-converter IC are also installed here.


Soldering quality is good.
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May 25th, 2022 07:15 EDT change timezone

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