Corsair AX1200i Digital ATX Power Supply Preview

The Corsair AX1200i Digital PSU features a fully modular design, which means all of its cables, including the ATX and EPS cables, can be removed. Some would argue that having a connector in-line with these critical power leads adds resistance and potentially dirties the feed, which is technically correct, but in practice the effects are minimal. Regardless, that’s the reason it’s common to find partially modular power supplies on the market as well.

Corsair AX1200i Digital PSU: Fully Modular Connectors, 140mm Cooling Fan

In terms of its physical dimensions, the Corsair AX1200i isn’t any larger than other high-end power supplies in its class. The unit measures 50mm x 86mm x 200mm, not including any depth added by attached cables. Both sides of the unit are adorned with attractive “Corsair AX1200i” badges, while the top sports a single decal with technical specifications. The bottom of the unit is home to a single, 140mm cooling fan. The inside face of the AX1200 is loaded with modular connectors and a self-test button, while the outside face has a power switch and a 3-pin power cord receptacle.

The AX1200i’s technical specifications are impressive to say the least. The unit features a single +12v rail design with a max output rating of 100.4A, or 1204.8W. The +3.3v and +5v feeds are rated for 30A each. Corsair claims the units are tested at 50’C ambient temperature to derive these ratings, which is a higher temperature than where most power supplies are tested. Although the unit has a single +12v rail design, we should point out that the AX1200i’s DSP and digitally-controlled power output can be configured as a virtual multi-rail device as well, with individual PCI-E over-current protection (OCP) trip points. The AX1200i also features digital interleaved power factor (PF) and PWM control, Over-Voltage Protection (OVP) and Over-Current Protection (OCP) on the 12v, 5v, and 3.3v rails, Over-Temperature Protection (OTP), and Short-Circuit Protection (SCP).

The AX1200i's DSP Control Board Is visible in the foreground...

Although its relatively high output power rating is attractive, the real standout feature of the Corsair AX1200i is its digitally controlled power. The AX1200i is the first desktop PC power supply to use a DSP, or Digital Signal Processor, to provide ultra-tight voltage regulation, < +/- 1.5% on the +12v rail according to Corsair, with low ripple and noise that’s up to 3x better than the ATX specification. The DSP also allows for dynamic, on-the-fly performance tuning and optimization.

In addition to DSP control, the AX1200i features individual DC-DC regulation for its 3.3v, 5v and 12v rails, and secondary side synchronous rectification, which utilizes lower-loss MOSFETs than more conventional output rectification schemes. The modular connector board’s PCB is also comprised of 4-layers to ensure a better ground return plane, lower resistance and low voltage drops than less sophisticated modular PSUs.

The Corsair AX1200i features a server-grade power train architecture and uses high-temp, Japanese capacitors

The use of a DSP in the control circuit also allowed Corsair to decrease the number of discrete components within the PSU. And because the AX1200i uses Zero Voltage Switching and Zero Current Switching (ZVS / ZVC) technology as well, the end result is very high efficiency. In fact, the unit is rated for 92%+ efficiency and has earned an 80 PLUS Platinum rating. The integration of a DSP (and inclusion of a Corsair Link USB dongle) also gives the AX1200i the ability to interface with Corsair’s Corsair Link real-time monitoring and control software, which we’ll talk about on the next page.

Other features of the Corsair AX1200i Digital PSU include a low-noise 140mm PWM cooling fan and a handy self-test switch. The cooling fan ramps up based on load, but won’t even spin until the load on the PSU exceeds 30% or 360W. The high efficiency of the PSU also results in less heat output than typical power supplies though, which minimizes the need for loud, active cooling. Throughout our real-world testing, the fan in the AX1200i was barely audible. Even when we manually cranked the fan speed up to 100%, it was still very quiet and barely audible over our other system components.

The self-test switch is also something new to the desktop PSU world, at least in our experience. With a push of a button, the AX1200i will run a series of diagnostic tests to ensure the cooling fan and DC output voltage rails are working properly. We hope you’ll never have to use it, but the inclusion of a self-test switch is a quick, simple way to test the PSU and could save users considerable time when diagnosing system failures.