[nextpage title=”Introduction”]
Corsair recently released the third version of their popular TX power supply series, dubbed “M” for “Modular.” However, it is really important to understand that this new version isn’t simply a TX or TX V2 power supply with a modular cabling system added; the internal design is completely different. The TX M series has 550 W, 650 W, 750 W, and 850 W models, all with 80 Plus Bronze certification. (The TX V2 series doesn’t have a 550 W version, and Corsair still offers a 950 W model under the first TX series.) We’ve already reviewed the 750 W version of the TX M series; now it is time to review the entry-level, 550 W model.
The manufacturer behind the TX M series is CWT, the same manufacturer that was in charge of the first version of the TX series. The TX V2 series, however, is manufactured by a different company (Seasonic). Therefore, the TX M series power supplies can’t be TX V2 units with a modular cabling system added.
Figure 1: Corsair TX550M power supply
Figure 2: Corsair TX550M power supply
The Corsair TX550M is 6.3” (160 mm) deep, using a 140 mm ball bearing fan on its bottom (Yate Loon D14BH-12).
This unit has a modular cabling system with four connectors, two for video cards (blue) and two for SATA and peripheral power connectors (black). The power supply comes with four cables permanently attached to it, and they 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, 18.5” (47 cm) long, permanently attached to the power supply
- One cable with two ATX12V connectors that together form an EPS12V connector, 23.6” (60 cm) long, permanently attached to the power supply
- Two cables, each with one six/eight-pin connector for video cards, 23.6” (60 cm) long, modular cabling system
- One cable with three SATA power connectors, 13.8” (35 cm) to the first connector, 5.9” (15 cm) between connectors, permanently attached to the power supply
- One cable with three SATA power connectors, 15.4” (39 cm) to the first connector, 5.9” (15 cm) between connectors, modular cabling system
- One cable with three standard peripheral power connectors, 14.6” (37 cm) to the first connector, 5.9” (15 cm) between connectors, permanently attached to the power supply
- One cable with three standard peripheral power connectors, 15” (38 cm) to the first connector, 5.9” (15 cm) between connectors, modular cabling system
- Two adapters to convert a standard peripheral power connector into a floppy disk drive power connector
All wires are 18 AWG, which is the minimum recommended gauge.
The cable configuration is adequate for a 550 W power supply.
Figure 3: Cables
Let’s now take an in-depth look inside this power supply.
[nextpage title=”A Look Inside the Corsair TX550M”]
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.
Figure 4: Top view
Figure 5: Front quarter view
Figure 6: Rear quarter view
Figure 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.
In this stage, this power supply is flawless, with one X capacitor and two Y capacitors more than the minimum required.
Figure 8: Transient filtering stage (part 1)
Figure 9: Transient filtering stage (part 2)
On the next page, we will have a more detailed discussion about the components used in the Corsair TX550M.
[nextpage title=”Primary Analysis”]
On this page we will take an in-depth look at the primary stage of the Corsair TX550M. For a better understanding, please read our “Anatomy of Switching Power Supplies” tutorial.
This power supply uses one GBU1006 rectifying bridge, which is attached to an individual heatsink. This bridge supports up to 10 A at 100° C, so in theory, you would be able to pull up to 1,150 W from a 115 V power grid. Assuming 80% effi
ciency, the bridge would allow this unit to deliver up to 920 W without burning itself out. Of course, we are only talking about this particular component. The real limit will depend on all the components combined in this power supply.
Figure 10: Rectifying bridge
The active PFC circuit uses only one transistor, an IPW60R190E6, which supports up to 20.2 A at 25° C or 12.8 A at 100° C in continuous mode (note the difference temperature makes), or 59 A at 25° C in pulse mode. These transistors present a 190 mΩ 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. Notice in Figure 11 how the manufacturer added a metal plate between the transistor and its heatsink in order to improve thermal dissipation.
Figure 11: The active PFC transistor
The output of the active PFC circuit is filtered by a Japanese capacitor, from Chemi-Con, labeled at 105° C.
In the switching section, two MDF18N50 MOSFETs are used in the traditional two-transistor forward configuration. Each of these transistors supports up to 18 A at 25° C or 11 A at 100° C in continuous mode (note the difference temperature makes), or 72 A at 25° C in pulse mode, with a 220 mΩ RDS(on).
Figure 12: The switching transistors
The primary is controlled by the omnipresent CM6800 active PFC/PWM combo controller.
Figure 13: Active PFC/PWM combo controller
Let’s now take a look at the secondary of this power supply.
[nextpage title=”Secondary Analysis”]
The Corsair TX550M 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. This design improves efficiency.
The +12 V output uses five STPS3045CT Schottky rectifiers (30 A, 15 A per internal diode at 155° C, 0.84 V maximum voltage drop).
Figure 14: +12 V rectifiers
As explained, the +5 V and +3.3 V outputs are produced by two DC-DC converters, which are physically located on the modular cabling printed circuit board. They are controlled by an APW7159 integrated circuit, using eight AP72T03GH MOSFETs, four for each output. Each transistor supports up to 62 A at 25° C or 44 A at 100° C in continuous mode, up to 190 A at 25° C in pulse mode, and 9 mΩ RDS(on).
Figure 15: The DC-DC converters
Figure 16: The DC-DC converters
This power supply uses a WT7502 monitoring integrated circuit, which is a very simple chip, supporting only over voltage (OVP) and under voltage (UVP) protections. On the solder side of the printed circuit board shown in Figure 17, there is an LM393 voltage comparator, which we guess makes the missing protections.
Figure 17: Monitoring circuit
The electrolytic capacitors that filter the +12 V output are also Japanese, from Chemi-Con, and are labeled at 105° C, as usual, while the capacitors that filter the +5 V and +3.3 V outputs are solid. See Figure 15.
[nextpage title=”Power Distribution”]
In Figure 18, you can see the power supply label containing all the power specs.
Figure 18: Power supply label
This power supply 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 t
he power supply’s single +12 V rail.
| 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 A (5 W) | 1.5 A (7.5 W) | 2 A (10 W) | 2.5 A (12.5 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 | 115.8 W | 220.2 W | 334.6 W | 446.2 W | 546.8 W |
| % Max Load | 21.1% | 40.0% | 60.8% | 81.1% | 99.4% |
| Room Temp. | 47.4° C | 45.7° C | 45.5° C | 46.1° C | 47.7° C |
| PSU Temp. | 51.1° C | 52.8° C | 52.6° C | 52.8° C | 53.6° C |
| Voltage Regulation | Pass | Pass | Pass | Pass | Pass |
| Ripple and Noise | Pass | Pass | Pass | Pass | Pass |
| AC Power | 137.5 W | 254.6 W | 388.8 W | 525.3 W | 654.0 W |
| Efficiency | 84.2% | 86.5% | 86.1% | 84.9% | 83.6% |
| AC Voltage | 116.6 V | 116.2 V | 113.7 V | 111.8 V | 110.5 V |
| Power Factor | 0.980 | 0.993 | 0.996 | 0.997 | 0.997 |
| Final Result | Pass | Pass | Pass | Pass | Pass |
The Corsair TX550M passed our tests with flying colors.
Efficiency was between 83.6% and 86.5% during our tests, which is terrific. It is great to see that this unit can really present efficiency above 82% at full load under higher temperatures, since several power supplies with the 80 Plus Bronze certification fail to provide 82% minimum efficiency under this scenario.
Voltages were closer to their nominal values (3% regulation) during all tests, which is what we want to see to consider a power supply “perfect.” 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 Corsair TX550M provided extremely low ripple and noise levels, as you can see in the table below.
| Input | Test 1 | Test 2 | Test 3 | Test 4 | Test 5 |
| +12VA | 12.6 mV | 15.2 mV | 20.2 mV | 26.8 mV | 34.4 mV |
| +12VB | 14.2 mV | 17.4 mV | 24.6 mV | 34.4 mV | 44.0 mV |
| +5 V | 8.6 mV | 8.2 mV | 7.8 mV | 8.8 mV | 8.8 mV |
| +3.3 V | 6.8 mV | 6.8 mV | 7.2 mV | 7.6 mV | 7.4 mV |
| +5VSB | 9.2 mV | 10.8 mV | 12.4 mV | 14.2 mV | 16.8 mV |
| -12 V | 18.8 mV | 26.6 mV | 40.8 mV | 55.6 mV | 68.2 mV |
Below you can see the waveforms of the outputs during test five.
Figure 19: +12VA input from load tester during test five at 546.8 W (34.4 mV)
Figure 20: +12VB input from load tester during test five at 546.8 W (44.0 mV)
Figure 21: +5V rail during test five at 546.8 W (8.8 mV)
Figure 22: +3.3 V rail during test five at 546.8 W (7.4 mV)
Let’s see if we can pull more than 550 W from this unit.
[nextpage title=”Overload Tests”]
Below you can see the maximum we could pull from this power supply. We couldn’t pull more than that because the power supply shut down, showing that its protections were working well. During this test, all voltages were still inside the tighter 3% regulation. Ripple and noise levels on the +12 V and -12 V outputs, however, skyrocketed to 138.4 mV and 115.6 mV, respectively. Efficiency was still above 82%, which is outstanding.
| Input | Overload Test |
| +12VA | 23 A (276 W) |
| +12VB | 23 A (276 W) |
| +5 V | 8 A (40 W) |
| +3.3 V | 8 A (23.4 W) |
| +5VSB | 3 A (15 W) |
| -12 V | 0.5 A (6 W) |
| Total | 638.4 W |
| % Max Load | 116.1% |
| Room Temp. | 44.9° C |
| PSU Temp. | 52.8° C |
| AC Power | 772 W |
| Efficiency | 82.7% |
| AC Voltage | 111.1 V |
| Power Factor | 0.998 |
[nextpage title=”Main Specifications”]
The main specifications for the Corsair TX550M power supply include:
- Standards: ATX12V 2.31 and EPS12V 2.92
- Nominal labeled power: 550 W
- Measured maximum power: 638.4 W at 44.9° C
- Labeled efficiency: 85% minimum at 50% load (i.e., 275 W), 80 Plus Bronze certification
- Measured efficiency: Between 83.6% and 86.1%, 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 separate cables
- SATA Power Connectors: Six on two cables, one permanently attached to the power supply
- Peripheral Power Connectors: Six on two cab
les, one permanently attached to the power supply - Floppy Disk Drive Power Connectors: Two using adapters
- Protections (as listed by the manufacturer): NA
- Are the above protections really available? The monitoring integrated circuit only supports over voltage (OVP) and under voltage (UVP) protections. Over power (OPP) and short-circuit (SCP) protections are present.
- Warranty: Five years
- Real Manufacturer: CWT
- More Information: https://www.corsair.com
- Average Price in the US*: USD 100.00
* Researched at Newegg.com on the day we published this review.
[nextpage title=”Conclusions”]
We were very impressed by the Corsair TX550M power supply, which proved to be a flawless product, with high efficiency between 83.6% and 86.1% at high temperatures, voltages closer to their nominal values than required (3% regulation), and extremely low noise and ripple levels.
At USD 100, this unit is not the cheapest 550 W power supply around, but if you are the kind of user who prefers to pay a little bit more to have a better product, the Corsair TX550M is the right choice.