Rosewill Capstone Modular 750 W 0

Rosewill Capstone Modular 750 W

Voltage Regulation & Efficiency »

A Look Inside

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


The OEM of this unit is Super Flower, a company which righteous earned a place among the elite PSU manufacturers thanks to their top performing and high quality products, which usually feature a very good price/performance ratio. The platform that the new Capstone is based on utilizes a resonant converter to achieve higher efficiency and in the secondary synchronous rectification is used along with two DC-DC converters for the generation of the minor rails. As you can see this is a modern platform worthy of a PSU that plays in the high-end category.


On the AC receptacle there aren't any transient filtering components since all are installed on the main PCB. Here we found three X caps, two pairs of Y caps (the second after the bridge rectifier) and two CM chokes. Unfortunately Super Flower didn't equip the transient filter with an MOV. Finally, as you can see the On/Off switch is connected to the main PCB through a large two pin connector. This makes removal of the main PCB (e.g. for servicing purposes) a breeze since you don't have to desolder anything. We wish all OEMs would use this method to connect the main PCB with the power wires. This would be also a blessing for all PSU reviewers, at least to the ones that don't have a desoldering station.


The bridge rectifier is bolted to the PFC/primary heatsink and a smaller one. Its model number is GBU1506 and it can handle up to 15A of power. Here we should note that once we removed the above heatsink to our surprise we discovered that there was no thermal compound between the heatsinks and the bridge so thermal dissipation is restricted. Apparently this isn't much of a problem since the bridge is already strong enough to cope with this unit's energy demands but nevertheless we applied some thermal grease to this area before we re-assembled the unit.


The APFC uses two IPW50R140CP fets along with a boost diode (CREE C3D06060) to shape the input current sinusoidal and boost the pulsating rectified mains up to a loosely regulated ~380V DC bus voltage. The single hold up cap is provided by Nippon Chemi-Con (560μF, 400V, 105°C, KMQ series). Between the aforementioned cap and the PFC choke we find a thermistor, responsible for protection against large inrush currents and a relay to bypass it once it finishes its job.


The PFC controller, an NCP1653A IC, is installed on a small vertical daughter-board located next to the APFC choke. It is protected from EMI/RFI by yellow vinyl tape and a thin copper shield which is totally covered by the tape.


The main choppers are a pair of Infineon IPP50R199CP fets.


The standby PWM controller is an ICE3B0565 IC.


The secondary heatsink houses four IPP041N04N fets. This type of fets have an Rds(on) value of 4.1 mΩ meaning that when they are fully conducting their resistance is 4.1 mΩ. Briefly for those who don't know anything about Rds(on), the higher this value is the more energy dissipation we have on the fets so efficiency takes a big hit especially as the load increases.


All filtering capacitors in the secondary side are Japanese (Chemi-Con) and along with the electrolytics (all rated at 105°C, KZE series) we also find several polymer ones.


Both Voltage Regulation Modules (VRMs) are housed on the same PCB and four metal plates shield the mosfets from EMI/RFI noise.


The role of the LLC controller along with the supervisor duties in the secondary side, handles a propriety SF29601 IC. It is housed on a vertical PCB in the secondary and on the rear side of the same PCB we find an LM324A Quad Operation Amplifier to assist in the protections scheme.


On the front side of the modular PCB there are some extra filtering Nippon caps. On the rear side soldering quality is good although not top notch.


Soldering quality on the main PCB is well above average but still cannot match the high-end implementations of Delta and Seasonic. Nevertheless Super Flower is catching up in this area and in the near future we expect them to match the soldering quality of the above two OEMs that so far dominated the PSU manufacturing field (with some exceptions of course, e.g. Flextronics Corsair AX1200).


The cooling fan wears Rosewill's logo but its model number (RL4ZB1402512M) reveals that it is actually made by Globe Fan. It uses ball bearings, so it has an extended lifetime compared to a sleeved bearings one and it can reach up to 1200RPM with 24.9dBA max noise output, so it is considered a quiet fan. This pdf provides further information about the specific fan.
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