Corsair HXi Series 750 W Review 13

Corsair HXi Series 750 W Review

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. Our main tool for the disassembly of the PSU is a Thermaltronics TMT-9000S soldering and rework station. It is of extreme quality and is equipped with a matching de-soldering gun. With such equipment in hand, breaking apart every PSU is like a walk in the park!

Corsair HX750i Parts Description
Primary Side
Transient Filter6x Y caps, 2x X caps, 2x CM chokes,
1x MOV
Bridge Rectifier(s)1x GBJ25L06
Inrush Current ProtectionNTC Thermistor & Relay
APFC Mosfets2x Infineon IPP50R140CP
APFC Boost Diode1x C3D08060A
Hold-up Cap(s)2x Nippon Chemi-Con (400V, 390uF each, 105°C, KMR)
Main Switchers2x Infineon IPP50R140CP
APFC ControllerInfineon ICE3PCS01G - CM03X
Digital ControllerPIC32MX
Switching ControllerInfineon ICE2HS01G
Secondary Side
+12V6x Infineon BSC014N04LS
5V & 3.3VDC-DC Converters: 6x M3004D fets
PWM Controller: APW7159
Filtering CapacitorsElectrolytics: Chemi-Con (KZE, 105C)
Polymers: Apaq, Enesol
Supervisor ICWeltrend WT7502 & 2x Weltrend WT7518
Fan ModelNR135L (12 V, 0.22 A, Fluid Dynamic Bearing)
5VSB Circuit
Rectifying DiodePFR20V45CT
Standby PWM Controller-

This is the exact same platform as in the HX1000i we reviewed a while ago, with some small component changes since this unit's maximum power output is lower. As you can see in the table above, analog components control most of the unit's functions, while an MCU (microcontroller) is the digital link between the analog controllers and the Corsair Link software. The software's only control functions are its ability to change the fan's speed and to toggle between single and multi +12V-rail mode; the PSU is set to multi +12V-rail mode by default. The primary side uses a half-bridge topology and an LLC resonant converter, while mosfets generate the +12V rail in the secondary side. Two DC-DC converters also generate the minor rails. Like the 1 kW unit, the primary side's heatsinks are pretty small, and there are no actual heatsinks in the secondary side.

We would also like to mention a weird rattling sound whenever we turned the unit upside down or even shook it slightly, and while we had our suspicions, we were only sure once we took the unit apart: a screw was the cause, and it didn't belong anywhere in particular. This screw apparently fell into the unit during the assembly process, or through the fan grill. It could have easily caused a short, and we wonder how Corsair's engineers missed it considering the fact that this specific unit was pre-tested by one since it was accompanied by a Chroma report. However, mistakes can happen, although such significant ones could easily lead to a dangerous short. You hopefully won't run into such a unit, but as a general rule, we advise you to shake a new PSU you buy for your system a bit before installing it. If you hear any strange sounds that could somehow be indicative of a lose part, make sure to have it replacemed. The above is surely an unorthodox testing method, but it can still save you from a world of hurt.

Two Y caps are installed at the AC receptacle, and there are another four Y caps, of which two are right after the bridge rectifier, two X caps, two CM chokes, and an MOV on the main PCB. As such, the transient filter is exactly the same as in the HX1000i.

A single GBJ25L06 bridge rectifier, bolted to a dedicated heatsink, is used, and it can handle up to 25 A, which are more than enough for this unit.

The APFC converter utilizes two Infineon IPP50R140CP fets and a C3D08060A boost diode. Both bulk caps are provided by Nippon Chemi-Con (400V, 390 uF each or 780 uF combined, 105°C, KMR series).

There is obviously an NTC thermistor for protection against large inrush currents, and the electromagnetic relay that isolates it from the circuit once it finishes its job, which increases the PSU's efficiency a bit and allows the thermistor to cool down faster.

Like in the HX1000i, the APFC controller, an Infineon ICE3PCS01G, and a CM03X Green PFC controller are on a vertical daughter-board right next to the APFC's choke. The same board also contains the resonant controller, an Infineon ICE2HS01G IC.

The main switchers are two Infineon IPP50R140CP fets.

As has already been mentioned, there are no heatsinks in the secondary side. All mosfets that generate the +12V rail, six Infineon BSC014N04LSs, reside on two vertical daughter-boards with four Chemi-Con electrolytic caps between them. Several bus bars on these boards not only transfer power, but also cool down the fets. Note that the HX1000i uses the exact same type and number of mosfets to generate the +12V rail, which makes this a particularly strong setup for the smaller HX750i.

Both VRMs (Voltage Regulation Modules) are on a large vertical PCB. The common PWM controller is an Anpec APW7159, and each VRM uses three M3004Ds. We also found an LM2904 op-amp amplifier on this PCB.

A Weltrend WT7502 supervisor IC is installed on the mainboard, and we also found two more WT7518 supervisor ICs on the modular PCB. These provide OCP for the +12V rail and can be disabled through Corsair Link if you prefer a single, powerful +12V rail.

We found the MCU (PIC32MX) that allows the PSU to talk with the Corsair Link software on this board. The latter application allows you to monitor and log fan speed and current, along with +3.3V, +5V, and +12V voltages. It can also control fan speed or monitor power-out, check power-in and efficiency, or enable and disable OCP on the +12V rails.

At the face of the modular PCB are many Enesol and Apaq polymer caps. These provide some extra ripple filtering. Some thick cables on the back of the same PCB transfer power to the modular sockets.

Soldering quality is good, without any ugly solder joints or long component leads.

The cooling fan is Corsair's favorite FDB fan with model number NR135P (12 V, 0.22 A). It'll last a long time since it utilizes a Fluid Dynamic Bearing. It also features a silent operation, enhanced by this unit's semi-passive option and relaxed fan profile.
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