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[nextpage title=”Introduction”]

The CAPSTONE M is the latest power supply series from Rosewill, coming with the 80 Plus Gold certification, Japanese capacitors, and now with a modular cabling system. Also, the manufacturer guarantees operation at 50° C. Available in 450 W, 550 W, 650 W, and 750 W versions, let’s see how the 550 W model fared in our tests.

This power supply series is manufactured by Super Flower, being a rebranded Super Flower SF-550P14XE unit, which is also sold as the Kingwin LZG-550.

Rosewill Capstone 550wFigure 1: Rosewill CAPSTONE-550M power supply

Rosewill Capstone 550wFigure 2: Rosewill CAPSTONE-550M power supply

The Rosewill CAPSTONE-550M is 6.7” (170 mm) deep, using a 140 mm ball bearing fan on its bottom (Rosewill RL4B1402512M, which is actually manufactured by Globe Fan).

The reviewed power supply has a modular cabling system with four connectors, which can be used by any SATA, peripheral or video card modular cable. The cables that are permanently attached to the power supply are protected with nylon sleeves that come from inside the unit. This power supply comes with the following cables:

  • Main motherboard cable with a 20/24-pin connector, 22.8” (58 cm) long, permanently attached to the power supply
  • One cable with two ATX12V connectors that together form an EPS12V connector, 25.2” (64 cm) long, permanently attached to the power supply
  • One cable with two six/eight-pin connectors for video cards, 18.5” (47 cm) to the first connector, 5.9” (15 cm) between connectors, modular cabling system
  • One cable with four SATA power connectors, 18.5” (47 cm) to the first connector, 5.9” (15 cm) between connectors
  • One cable with two SATA power connectors and two standard peripheral power connectors, 18.5” (47 cm) to the first connector, 5.9” (15 cm) between connectors
  • One cable with three standard peripheral power connectors and one floppy disk drive power connector, 18.5” (47 cm) to the first connector, 5.9” (15 cm) between connectors

All wires are 18 AWG, which is the minimum recommended gauge. The cable configuration is adequate for a 550 W unit.

Rosewill Capstone 550wFigure 3: Cables

Let’s now take an in-depth look inside this power supply.

[nextpage title=”A Look Inside the Rosewill CAPSTONE-550M”]

We decided to disassemble this power supply to see what it looks like inside, how it is designed, and what components are used. Please read our “Anatomy of Switching Power Supplies” tutorial to understand how a power supply works and to compare this power supply to others.

On this page we will have an overall look, and then in the following pages we will discuss in detail the quality and ratings of the components used.

Rosewill Capstone 550wFigure 4: Top view

Rosewill Capstone 550wFigure 5: Front quarter view

Rosewill Capstone 550wFigure 6: Rear quarter view

Rosewill Capstone 550wFigure 7: The printed circuit board

[nextpage title=”Transient Filtering Stage”]

As we have mentioned in other articles and reviews, the first place we look when opening a power supply for a hint about its quality, is its filtering stage. The recommended components for this stage are two ferrite coils, two ceramic capacitors (Y capacitors, usually blue), one metalized polyester capacitor (X capacitor), and one MOV (Metal-Oxide Varistor). Very low-end power supplies use fewer components, usually removing the MOV and the first coil. 

Even though this power supply has two X capacitors more than the minimum required, it doesn’t have an MOV, which is the component in charge of absorbing spikes coming from the power grid.

Rosewill Capstone 550wFigure 8: Transient filtering stage

On the next page, we will have a more detailed discussion about the components used in the Rosewill CAPSTONE-550M.

[nextpage title=”Primary Analysis”]

On this page we will take an in-depth look at the primary stage of the Rosewill CAPSTONE-550M. For a better understanding, please read our “Anatomy of Switching Power Supplies” tutorial.

This power supply uses one GBU806 rectifying bridge, which is attached to the same heatsink as the active PFC and switching transistors. This bridge supports up to 8 A at 100° C. So, in theory, you would be able to pull up to 920 W from a 115 V power grid. Assuming 80% efficiency, the bridge would allow this unit to deliver up to 726 W without burning itself out. (Or 828 W at 90% efficiency.) Of course, we are only talking about this particular component. The real limit will depend on all the components combined in this power supply.

Rosewill Capstone 550wFigure 9: Rectifying bridge

The active PFC circuit uses one IPW60R165CP MOSFET. This transistor supports up to 21 A at 25° C or 13 A at 100° C in continuous mode (see the difference temperature makes) or up to 61 A at 25° C in pulse mode. This transistor p
resents a 165 mΩ maximum resistance when turned on, a characteristic called RDS(on). The lower the number the better, meaning that the transistor will waste less power, and the power supply will have a higher efficiency.

The active PFC circuit is controlled by an NCP1653A integrated circuit.

Rosewill Capstone 550wFigure 10: Active PFC controller

The output of the active PFC circuit is filtered by one 390 µF x 400 V Japanese electrolytic capacitor, from Chemi-Con, labeled at 85° C.

In the switching section, two IPA50R250CP MOSFETs are used in a resonant configuration. Each supports up to 13 A at 25° C or 9 A at 100° C in continuous mode or 31 A at 25° C in pulse mode, with a maximum RDS(on) of 250 mΩ.

Rosewill Capstone 550wFigure 11: Active PFC transistors, active PFC diode, and one of the switching transistors

The switching transistor is managed by an SF29601 resonant controller, which is a custom solution from Super Flower. This integrated circuit is located in the secondary and also provides the necessary protection circuitry.

Rosewill Capstone 550wFigure 12: Resonant controller

Let’s now take a look at the secondary of this power supply.

[nextpage title=”Secondary Analysis”]

The Rosewill CAPSTONE-550M uses a DC-DC design in its secondary. This means that the power supply is basically a +12 V unit, with the +5 V and +3.3 V outputs produced by two smaller power supplies connected to the main +12 V rail. Also, the +12 V output uses a synchronous design where the rectifiers were replaced with MOSFETs. Both designs are used to increase efficiency.

The +12 V output uses four IPP041N04N G MOSFETs, each one supporting up to 80 A at 100° C in continuous mode or up to 400 A at 25° C in pulse mode, with a maximum RDS(on) of 4.1 mΩ.

Rosewill Capstone 550wFigure 13: Two of the four +12 V transistors

As explained, the +5 V and +3.3 V outputs are produced by two DC-DC converters. Both are located on the same daughterboard that is soldered to the main printed circuit board. Each converter is controlled by an NCP1587A integrated circuit and uses two ME70N03S MOSFETs. Each transistor supports up to 62 A at 25° C or 50 A at 70° C in continuous mode or up to 100 A at 25° C in pulse mode, with a maximum RDS(on) of 11 mΩ. 

Rosewill Capstone 550wFigure 14: The DC-DC converter

Rosewill Capstone 550wFigure 15: The DC-DC converter

The outputs of this power supply are monitored by the resonant controller, which doubles as the monitoring circuit.

The electrolytic capacitors that filter the outputs are also Japanese, from Chemi-Con, and labeled at 105° C, as usual.

[nextpage title=”Power Distribution”]

In Figure 16, you can see the power supply label containing all the power specs.

Rosewill Capstone 550wFigure 16: Power supply label

As you can see, this unit has a single +12 V rail, so there is not much to talk about here.

How much power can this unit really deliver? Let’s find out.

[nextpage title=”Load Tests”]

We conducted several tests with this power supply, as described in the article, “Hardware Secrets Power Supply Test Methodology.” 

First we tested this power supply with five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity (actual percentage used listed under “% Max Load”), watching the behavior of the reviewed unit under each load. In the table below, we list the load patterns we used and the results for each load.

If you add all the powers listed for each test, you may find a different value than what is posted under “Total” below. Since each output can have a slight variation (e.g., the +5 V output working at +5.10 V), the actual total amount of power being delivered is slightly different than the calculated value. In the “Total” row, we are using the real amount of power being delivered, as measured by our load tester.

The +12VA and +12VB inputs listed below are the two +12 V independent inputs from our load tester. During this test, both inputs were connected to the power supply’s single +12 V rail. (The power supply’s EPS12V connector was installed on the +12VB input of the load tester.)

Input Test 1 Test 2 Test 3 Test 4 Test 5
+12VA 4 A (48 W) 8 A (96 W) 12 A (144 W) 16.5 A (198 W) 20 A (240 W)
+12VB 4 A (48 W) 8 A (96 W) 12 A (144 W) 16 A (192 W) 20 A (240 W)
+5 V 1 A (5 W) 2 A (10 W) 4 A (20 W) 5 A (25 W) 6 A (30 W)
+3.3 V 1 A (3.3 W) 2 A (6.6 W) 4 A (13.2 W) 5 A (16.5 W) 6 A (19.8 W)
+5VSB 1 A (5 W) 1.5 A (7.5 W) 2 A (10 W) 2.5 A (12.5 W) 3 A (15 W)
-12 V 0.5 A (6 W) 0.5 A (6 W) 0.5 A (6 W) 0.5 A (6 W) 0.5 A (6 W)
Total 116.5 W 220.8 W 334.5 W 450.5 W 548.8 W
% Max Load 21.2% 40.1% 60.8% 81.9% 99.8%
Room Temp. 45.3° C 44.8° C 45.2° C 46.2° C 47.6° C
PSU Temp. 46.9° C 46.0° C 45.8° C 46.8° C 48.6° C
Voltage Regulation Pass Pass Pass Pass Pass
Ripple and Noise Pass Pass Pass Pass Pass
AC Power 129.8 W 243.3 W 373.5 W 513.2 W 634.0 W
Efficiency 89.8% 90.8% 89.6% 87.8% 86.6%
AC Voltage 115.4 V 114.6 V 114.3 V 111.6 V 110.5 V
Power Factor 0.981 0.990 0.993 0.994 0.995
Final Result Pass Pass Pass Pass Pass

The Rosewill CAPSTONE-550M passed our tests with flying colors.

Efficiency was between 86.6% and 90.8%, virtually matching the 80 Plus Gold certification, which promises a minimum efficiency of 87% at light (i.e., 20%) and full loads, and 90% at typical (i.e., 50%) load. The small difference between what is promised (87%) and what we’ve seen (86.6%) during our full load test can be easily explained by AC voltage, which dropped from 115 V to 110 V, and also by the higher temperature under which we test power supplies.

Voltages were always closer to their nominal values than required (i.e., 3% regulation). The ATX12V specification states that positive voltages must be within 5% of their nominal values, and negative voltages must be within 10% of their nominal values.

Let’s discuss the ripple and noise levels on the next page.

[nextpage title=”Ripple and Noise Tests”]

Voltages at the power supply outputs must be as “clean” as possible, with no noise or oscillation (also known as “ripple”). The maximum ripple and noise levels allowed are 120 mV for +12 V and -12 V outputs, and 50 mV for +5 V, +3.3 V and +5VSB outputs. All values are peak-to-peak figures. We consider a power supply as being top-notch if it can produce half or less of the maximum allowed ripple and noise levels.

The Rosewill CAPSTONE-550M provided extremely low noise and ripple levels, as you can see below.

Input Test 1 Test 2 Test 3 Test 4 Test 5
+12VA 12.4 mV 16.4 mV 23.8 mV 30.2 mV 36.8 mV
+12VB 11.8 mV 16.4 mV 22.2 mV 30.4 mV 38.2 mV
+5 V 7.4 mV 8.4 mV 9.0 mV 10.2 mV 10.6 mV
+3.3 V 8.8 mV 10.0 mV 12.6 mV 13.8 mV 16.8 mV
+5VSB 6.6 mV 7.6 mV 8.8 mV 9.4 mV 11.2 mV
-12 V 9.8 mV 10.2 mV 12.6 mV 15.4 mV 14.4 mV

Below you can see the waveforms of the outputs during test five.

Rosewill Capstone 550wFigure 17: +12VA input from load tester during test five at 548.8 W (36.8 mV)

Rosewill Capstone 550wFigure 18: +12VB input from load tester during test five at 548.8 W (38.2 mV)

Rosewill Capstone 550wFigure 19: +5V rail during test five at 548.8 W (10.6 mV)

Rosewill Capstone 550wFigure 20: +3.3 V rail during test five at 548.8 W (16.8 mV)

[nextpage title=”Overload Tests”]

Below you can see the maximum we could pull from this power supply. The objective of this test is to see if the power supply has its protection circuits working properly. This unit passed this test, as it shut down if we tried to pull more than listed below. Noise and ripple levels increased, but were still below the maximum allowed. All voltages were still within 3% of their nominal values.

Input Overload Test
+12VA 23 A (276 W)
+12VB 23 A (276 W)
+5 V 8 A (40 W)
+3.3 V 8 A (26.4 W)
+5VSB 3 A (15 W)
-12 V 0.5 A (6 W)
Total 625.8 W
% Max Load 113.8%
Room Temp. 47.9° C
PSU Temp. 52.4° C
AC Power 744.0 W
Efficiency 84.1%
AC Voltage 109.3 V
Power Factor 0.996

[nextpage title=”Main Specifications”]

The main specifications for the Rosewill CAPSTONE-550M power supply include:

  • Standards: ATX12V 2.31 and EPS12V 2.92
  • Nominal labeled power: 550 W
  • Measured maximum power: 625.8 W at 47.9° C
  • Labeled efficiency: Between 87% and 92%, 80 Plus Gold certification
  • Measured efficiency: Between 86.6% and 90.8%, at 115 V (nominal, see complete results for actual voltage)
  • Active PFC: Yes
  • Modular Cabling System: Yes
  • Motherboard Power Connectors: One 20/24-pin connector and two ATX12V connectors that together form an EPS12V connector, permanently attached to the power supply
  • Video Card Power Connectors: Two six/eight-pin connectors on one cable, modular cabling
  • SATA Power Connectors: Six on two cables, modular cabling
  • Peripheral Power Connectors: Five on two cables, modular cabling
  • Floppy Disk Drive Power Connectors: One, modular cabling
  • Protections (as listed by the manufacturer): Over voltage (OVP), over current (OCP), over power (OPP), and short-circuit (SCP)
  • Are the above protections really available? Yes
  • Warranty: Five years
  • Real Model: Super Flower SF-550P14XE
  • More Information: https://www.rosewill.com
  • Average Price in the U.S.*: USD 100.00

* Researched at Newegg.com on the day we published this review.

[nextpage title=”Conclusions”]

The Rosewill CAPSTONE-550M is an outstanding power supply that passed our tests with flying colors. All voltages were within 3% of their nominal values all the time, ripple and noise levels were extremely low, and efficiency was always high.

The original CAPSTONE-550 is sold today for USD 80, while the new version with a modular cabling system is sold for USD 100. We think that paying USD 20 for the modular cabling o
ption is too much for a low-wattage power supply that doesn’t have a lot of cables. In our opinion, the original CAPSTONE-550 provides a better price/performance ratio than the new CAPSTONE-550M. Still, the new unit is an excellent power supply that won’t disappoint.