Corsair HX750i: the basis for RMi series

Primary side

The layout is highly familiar, but there is more components. First we have the Vishay LVB1560 bridge rectifier, capable of delivering 15 A continuously at 600 V and 125 °C (or 400 A peak for 8.3 ms at 25 °C). It has its own black aluminium heatsink. The voltage drop (counting for losses) is just 0.9 V per diode at 7.5 A. Then there is quite massive PFC choke, triple insulated on the bottom side (PCB + tape + epoxy). The power silicon operating the PFC consists of two transistors and a diode this time, but still have separate heatsink. They are the Infineon IPA50R140CP (23/56 A at 550 V and 25 °C, RDS(On) 0.14 Ω at 14 A and 25 °C, 0.32 Ω at 150 °C) in TO-220FP package. The diode then is the usual Cree C3D08060 (23/220 A at 600 V and 25 °C, drop of 1.8 V at 25 °C or 2.4 V at 175 °C) in TO-220AC package.


As for the bulk cap charged from the PFC, there are two of them, both Nippon Chemi-Con KMR 390 μF/400 V. This series has a minimum lifetime of 2000 hours at maximum temperature (105 °C) and ripple. The switching transistors they feed are the same Infineon IPA50R140CP the PFC section uses, in half-bridge LLC resonant topology. The Infineon ICE2HS01G controller is used as a driver, while the ICE3PCS01G controls the boost-type PFC.


There is also the Champion Micro CM03X to reduce no-load (or low load) power consumption. All these three microchips are placed on the daughterboard (with EMI-shielded backside) located next to the switching transistor heatsink. Notice how it all forms separate corridors to channel the cooling air. A transformer with Corsair logo and 45 mm wide core is used to transfer the power to secondary side.

+5 V stand-by rail

The stand-by rail is the same as within the RMx/RMi units. It is being controlled by On-Bright OB5269CP flyback PWM microcontroller, which is powered directly from the input filtering section. It controlls Ubiq Semiconductor QM03N65D MOSFET (3/6 A at 650 V and 25 °C, RDS(On) 4 Ω at 1.5 A) in TO-252 SMD package (it is on the solder side of the board). Chemi-Con KY capacitors are used for feedback and other circuitry around the stand-by rail.


Corsair-labeled transformer with 20mm wide core is used for transformation and PFC Device Corporation PFR20V45CT (20/250 A at 45 V and 25 °C, drop of 0.47 V per diode at 10 A and 25 °C) rectifier for single-wave rectification. Chemi-Con caps are used again for the filtration, this time KZE 2200/16 and KY 1000/10. So far so good, though capacitor with longer lifetime rating than KZE could have been used (KZE has just 4000 hours for D10).

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