Corsair AX 860 W

Corsair AX 860 W

Voltage Regulation, Hold-up Time & Inrush Current »

A Look Inside & Component Analysis

Before reading this page, we strongly suggest a look at this article, which will help you understand the internal components of a PSU much better.


The previous AX generation was based on Seasonic's KM2 platform. The new AX units are still made by Seasonic, but they utilize the fresh KM3 platform that houses many improvements over the older one which, by the way, is still a solid performer. Below, you will find a short list of those improvements, which you will probably find pretty interesting.
  1. 12V Line regulation is ±2% instead of the ±3%
  2. Flat, Black DC Cables
    • Easier for system builds
      Looks match current chassis internals better
      Better for airflow in system
  3. Increased number of possible CPU/PCIe cable options
    • KM2 had, on the PSU side, 2x12Pin + 1x8Pin connectors for the CPU & PCIe cables
      KM3 has 5x8Pin, which offers extra cable options
  4. KM3 is Full Bridge as compared to KM2's Half Bridge
    • Improved reliability and efficiency
  5. MOSFETs on daughter card instead of main PCB
    • Improves space utilization on main PCB for safety and cooling
      Allows for increase of the ground-pad size on the main PCB, which improves efficiency
  6. 9A, 85°C high-current connectors
    • Added security and reliability


As usual, we will start our internal description by the transient filtering stage. It starts at the AC receptacle with a small PCB that houses four Y caps, a CM choke, and a single X cap. As you can see, the aforementioned PCB is fully covered by a metal shield for EMI suppression. On the main PCB, we find the other transient components. They include two CM chokes, two pairs of X and Y caps, and an MOV. This area also has the thermistor responsible for protection against large inrush currents and the corresponding electromagnetic relay that cuts it off the circuit once the start-up phase finishes.


As bridge rectifiers, two GBJ1506s are used, and they are quite powerful for this unit since each one can handle up to 15 A of current, which results in a combined total of 30 A being supported.


The standby Quasi-Resonant PWM Controller is an ICE2QR4765 IC.


In the APFC, two IPP60R125CP fets are used along with a CREE C3D08060A boost diode.


The PFC controller, an NPC1654 IC, is housed on this small vertical daughter-board.


The main switchers are four Infineon IPP50R250CPs arranged into a full-bridge topology. Exactly the same ones are used in the lower capacity AX760 unit. Along with the full-bridge topology, an LLC resonant converter is utilized for an efficiency boost.


The LLC resonant controller, a Champion CM6901 IC, is housed on a PCB in the secondary side. The same PCB also houses all +12V rectifying fets. For this platform (KM3), Seasonic technicians chose to remove the +12V fets from the solder side of the main PCB. They installed them on this board in order to provide them with better cooling. The second heatsink, used for the cooling of the +12V fets, has a thermistor that provides information to the fan-speed control circuit.

The secondary side mostly uses Chemi-Con electrolytic caps, but we also found some Enesol polymer caps, to cool down the +12V rectifying fets, under the heatsink.

The DC-DC converters that generate the minor rails are installed directly on the modular PCB for smaller energy losses during power transfers. Their PWM controller is an APW7159 IC, and each one uses three Infineon BSC0906NS fets.


Many Enesol polymer caps are installed on the front of the modular PCB for ripple filtering of the DC outputs. The two chokes are utilized by the DC-DC converters.


The supervisor IC is installed on a vertical PCB and is a Weltrend WT7527. We also found an LM393 dual-voltage comparator on the same PCB. The WT7527 supports OCP for up to two +12V virtual rails, but this PSU only has one.


Soldering quality on the main PCB is impeccable, something that goes without saying with Seasonic's high-end implementations.


The 120 mm diameter cooling fan, a San Ace 120, is provided by Sanyo Denki, and its quality is very high. It uses double ball-bearings, and its exact model number is 9S1212F404 (12 V, 0.19 A, 2.200 RPM, 70.6 CFM). The older AX750 and AX850 models used the same fan. Corsair wisely decided that there was no reason for a change with their new AX models.
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