Tom's Hardware Verdict

The Corsair AX850 is the best 850-watt PSU you can get, thanks to its high-efficiency and low noise levels, but you’ll pay a premium for it.

Pros

+
Quiet Operation
+
Efficient
+
Great performance overall
+
Long hold-up time
+
Top build quality
+
Ten-year warranty

Cons

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Expensive
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EPS connectors should use 16AWG wires
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Short distance between the peripheral connectors
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High OCP on the minor rails

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Specifications and Part Analysis

If you need the best 850W power supply and you don't have a restrictive budget, the AX850 should be among your top choices. It registers high performance in all areas: efficiency, load regulation, ripple suppression, transient response and, on top of that, it is dead silent as well. This unit is based on the Seasonic Prime Titanium platform, which is the best analog design today. With such great analogue platforms, someone could wonder why spend more on digital ones, where all major functions are controlled by micro-controllers instead of analogue ICs. As we see it, in the near future the AX860i will be probably replaced by the AX850, which easily meets its performance, although this is a bit of a paradox, a digital platform to get replaced by an analogue one.

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The higher the efficiency levels the lower the thermal loads, so the cooling fan has less work to do and can rotate at lower speeds. Large heat sinks can also help in this, with a recent example being the Rog Thor 1200W unit. Nonetheless, you still need high efficiency levels since if the heat sinks reach their limits, increased airflow will be needed to handle heat dissipation and keep the temperatures of the internals low.

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Manufacturer (OEM)	Seasonic
Max. DC Output	850W
Efficiency	80 PLUS Titanium, ETA-A+ (91-94%)
Noise	LAMBDA-A+ (15-20 dB[A])
Modular	✓ (Fully)
Intel C6/C7 Power State Support	✓
Operating Temperature (Continuous Full Load)	0 - 50°C
Over Voltage Protection	✓
Under Voltage Protection	✓
Over Power Protection	✓
Over Current (+12V) Protection	✓
Over Temperature Protection	✓
Short Circuit Protection	✓
Surge Protection	✓
Inrush Current Protection	✓
Fan Failure Protection	No
No Load Operation	✓
Cooling	135mm Fluid Dynamic Bearing Fan (HA13525L12F-Z)
Semi-Passive Operation	✓ (Selectable)
Dimensions (W x H x D)	152 x 87 x 172mm
Weight	2 kg (4.41 lb)
Form Factor	ATX12V v2.4, EPS 2.92
Warranty	10 Years

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Modular Cables
Description	Cable Count	Connector Count (Total)	Gauge	In Cable Capacitors
ATX connector 20+4 pin (610mm)	1	1	16-20AWG	Yes
4+4 pin EPS12V (650mm)	2	2	18AWG	Yes
6+2 pin PCIe (670mm+100mm)	4	8	16-18AWG	Yes
SATA (460mm+110mm+110mm+110mm)	4	16	18AWG	No
4 pin Molex (550mm+100mm+100mm)	2	6	18AWG	No
FDD Adapter (110mm)	1	1	22AWG	No
AC Power Cord (1400mm)	1	1	14AWG	-

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General Data
Manufacturer (OEM)	Seasonic
Platform Model	Prime
Primary Side
Transient Filter	6x Y caps, 3x X caps, 2x CM chokes, 1x MOV
Inrush Protection	NTC Thermistor & Relay
Bridge Rectifier(s)	2x Vishay LVB2560 (600V, 25A @ 105°C)
APFC MOSFETS	2x Infineon IPP60R099CP (650V, 19A @ 100°C, 0.099 Ohm)
APFC Boost Diode	1x CREE C3D10060 (600V, 10A @ 153°C)
Hold-up Cap(s)	2x Nippon Chemi-Con (400V, 680uF & 470uF or 1150uF combined, 2000h @ 105°C, KMR)
Main Switchers	4x Infineon IPP50R140CP (550V, 15A @ 100°C, 0.140 Ohm)
Drivers For Main Switchers	2x Silicon Labs Si8230BD
APFC Controller	ON Semiconductor NPC1654
Switching Controller	Champion CM6901
Topology	Primary side: Full-Bridge & LLC Resonant Converter Secondary side: Synchronous Rectification & DC-DC converters
Secondary Side
+12V MOSFETS	4x Infineon BSC014N04LS (40V, 100A @ 100°C, 1.4 mOhm)
5V & 3.3V	DC-DC Converters: 6x Infineon BSC0906NS PWM Controller: APW7159
Filtering Capacitors	Electrolytics: Nippon Chemi-Con (105°C, W, KYB) 1x Chemi-Con (5VSB circuit, 5-6,000h @ 105°C, KZH) Polymers: FPCAP, Nippon Chemi-Con
Supervisor IC	Weltrend WT7527V (OVP, UVP, OCP, SCP, PG )
Fan Model	Hong Hua HA13525L12F-Z (135mm, 12V, 0.22A, 1600 RPM, Fluid Dynamic Bearing)
5VSB Circuit
Buck Converter	Leadtrend LD7750R
Rectifiers	STMicroelectronics STU6N65K3 (650V, 3A @ 100°C, 1.3mOhm), Infineon BSC0906NS (30V, 40A @ 100°C, 4.5mOhm)
-12V Circuit
Buck Converter	Lite-On LSP5523 (3A max output current )

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In the primary side a full-bridge topology is utilized along with an LLC resonant converter, while in the secondary side we meet a synchronous rectification scheme and a pair of DC-DC converters, which regulate the minor rails. Finally, the mid-speed cooling fan is made by Hong Hua and it uses a fluid dynamic bearing, which besides a long lifetime also provides silent operation. The highly-relaxed fan profile plays a notable part as well, in keeping the noise low.

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