Introduction

We also like to review low-end products from time to time so people with a serious budget restriction can have an idea whether it is worthwhile to buy cheap products or not. Today we are going to take an in-depth look at eXtreme Power Plus 400 W (RS-400-PCAR-A3) from Cooler Master. Can it really deliver its rated power? Let’s see.

We’ve already reviewed the 460 W (RS-460-PMSR-A3) and 500 W (RS-500-PCAR-A3) models from this same series. The 460 W model wasn’t capable of delivering its labeled capacity and the 500 W model failed our tests because, even though it could deliver its labeled wattage, it presented a huge noise/ripple problem. Let’s see the fate of this 400 W model.

Members of eXtreme Power Plus series are manufactured by AcBel Polytech. It is important to note that Cooler Master has an older series called eXtreme Power (without the “Plus”) where the units are presumably manufactured by Seventeam.

By the way, how about the fantastic statement “As sealed stick was removed, lost or damaged, it shall be out of warranty validity” on the power supply label? When Chinese manufacturers will stop using on-line translators and hire someone that can speak English to write their labels?

Another interesting information from the label: “The +3.3 V & +5 V & +12V1 & +12V2 combine (sic) power shall not exceed 361.5 W.” Well, if you add this to the 12.5 W maximum power for the +5VSB output and 6 W maximum power for the -12 V output we have a 380 W power supply…

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Figure 1: Cooler Master eXtreme Power Plus 400 W power supply.

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Figure 2: Cooler Master eXtreme Power Plus 400 W power supply.

Cooler Master eXtreme Power Plus 400 W is 5 ½” (140 mm) deep, using a 120 mm fan on its bottom. This unit does not feature a PFC circuit, as you can see by the presence of a 115 V/230 V switch in Figure 1, but at least it is being based on a more modern design than the outdated half-bridge topology, as we will show.

No modular cabling system is provided and only the main motherboard cable have a nylon protection that comes from inside the power supply housing. Only the ATX12V/EPS12V cable use 18 AWG wires. All other wires are 20 AWG, i.e., thinner than recommended.

The cables included are:

• Main motherboard cable with a 20/24-pin connector, 15 ¾” (40 cm) long.
• One cable with two ATX12V connectors that together form one EPS12V connector, 21 5/8” (55 cm) long.
• One cable with one six-pin connector for video cards, 15 ¾” (40 cm) long.
• Two cables with two SATA power connectors and one peripheral power connector each, 15 ¾” (40 cm) to the first connector, 4 ¾” (12 cm) between connectors).
• One cable with three standard peripheral power connectors and one floppy disk drive power connector, 15 ¾” (40 cm) to the first connector, 4 ¾” (12 cm) between connectors.

This configuration is compatible with a low-end 400 W product.

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Figure 3: Cables.

Now let’s take an in-depth look inside this power supply.

A Look Inside The Cooler Master eXtreme Power Plus 400 W

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.

This page will be an overview, while in the following pages we will discuss the quality and ratings of the components used in detail.

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Figure 4: Overall look.

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Figure 5: Overall look.

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Figure 6: Overall look.

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 is an entry-level power supply, it has two MOV’s (installed between the two electrolytic capacitors from the voltage doubler) and three Y capacitors and one X capacitor more than the minimum recommended.

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Figure 7: Transient filtering stage (part 1).

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Figure 8: Transient filtering stage (part 2).

In the next page we will have a more detailed discussion of the components used in the Cooler Master eXtreme Power Plus 400 W.

Primary Analysis

On this page we will take an in-depth look at the primary stage of Cooler Master eXtreme Power Plus 400 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses two GBL06 rectifying bridges, each one supporting up to 4 A at 50º C if a heatsink is used, which is not the case, or up to 3 A at 40º C. At 115 V this unit would be able to pull up to 690 W from the power grid; assuming 80% efficiency, the bridges would allow this unit to deliver up to 552 W without burning themselves. Of course, we are only talking about these components, and the real limit will depend on all the other components in this power supply. Both the 460 W and 500 W versions of this power supplies use two 6 A bridges here.

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Figure 9: Rectifying bridges.

This unit is based on a single-transistor forward topology, which is good to see, since usually low-end units are based on the obsolete half-bridge design. Two 2SK4115 power MOSFET transistors are connected in parallel on the switching section. Each transistor is capable of handling up to 7 A at 25º C in continuous mode, or up to 21 A at 25º C in pulse mode, so the switching section can deliver up to 14 A at 25º C. Unfortunately the manufacturer does not provide the current limits at 100º C. These transistors present an RDS(on) of 1.6 Ω, which is very high (i.e., bad, low efficiency). This number measures the resistance provided by the transistors when they are turned on; the lower this number, the better (higher efficiency). The 460 W model uses different transistors here but with the same current limits, while the 500 W model uses more powerful 9 A transistors here.

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Figure 10: One of the switching transistors.

The switching transistors are controlled by a UC3843 PWM controller, which is located on the primary.

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Figure 11: PWM controller.

The two electrolytic capacitors from the voltage doubler are from Elite and labeled at 85º C.

Now let’s take a look at the secondary of this power supply.

Secondary Analysis

This power supply has four Schottky rectifiers on its secondary and an LM7912 voltage regulator in charge of the -12 V output.

The maximum theoretical current each line can deliver is given by the formula I / (1 - D), where D is the duty cycle used and I is the maximum current supported by the rectifying diode. Just as an exercise, we can assume a typical duty cycle of 30%.

The +12 V output is produced by two SBR20100CT Schottky rectifiers, each one supporting up to 20 A (10 A per internal diode at 150º C, 0.82 V maximum voltage drop), giving us a maximum theoretical current of 29 A or 343 W for the +12 V output. Both 460 W and 500 W models use rectifiers with the same specs.

The +5 V output is produced by one STPS3045CT Schottky rectifier, which supports up to 30 A (15 A per internal diode at 150º C, 0.84 V maximum voltage drop), giving us a maximum theoretical current of 21 A or 107 W for the +5 V output. The 460 W and 500 W models use two 20 A rectifiers connected in parallel here.

The +3.3 V output is produced by another STPS3045CT Schottky rectifier, giving us a maximum theoretical current of 21 A or 71 W for the +3.3 V output. The 460 W and 500 W models use two 20 A rectifiers connected in parallel here.

All these numbers are theoretical. The real amount of current/power each output can deliver is limited by other components, especially by the coils used on each output.

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Figure 12: -12 V voltage regulator, +3.3 V, +5 V and +12 V rectifiers.

The outputs are monitored by a WT7527 integrated circuit, which supports OVP (over voltage protection), UVP (under voltage protection) and OCP (over current protection). This circuit has four over current channels. Additionally this power supply has an LM339 integrated circuit (which has four voltage comparators inside) for other protections.

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Figure 13: Monitoring integrated circuit.

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Figure 14: Monitoring integrated circuit.

The electrolytic capacitors from the secondary are from Ltec.

Power Distribution

In Figure 15, you can see the power supply label containing all the power specs.

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Figure 15: Power supply label.

As you can see, according to the label this unit has two +12 V rails. Inside the unit we could clearly see two shunts (current sensors) and the monitoring integrated circuit used by this unit supports over current protection, so this unit really has two +12 V rails (click here to understand more about this subject). The two rails are divided like this:

• +12V1 (solid yellow wire): ATX12V/EPS12V connector.
• +12V2 (yellow with black stripe wire): All other connectors.

This is the typical distribution used on unit with two +12 V rails and it is good since it separates the CPU (ATX12V/EPS12V) from the video cards.

Now let’s see if this power supply can really deliver 400 W.

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 how the reviewed unit behaved 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 power listed for each test, you may find a different value than what is posted under “Total” below. Since each output can vary slightly (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. On 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 the +12VA input was connected to the power supply +12V2 rail, while +12VB was connected to the power supply +12V1 rail (EPS12V connector).

Input	Test 1	Test 2	Test 3	Test 4	Test 5
+12VA	2.5 A (30 W)	5.5 A (66 W)	8 A (96 W)	10.5 A (126 W)	14 A (168 W)
+12VB	2.5 A (30 W)	5.5 A (66 W)	8 A (96 W)	10.5 A (126 W)	13 A (156 W)
+5V	1 A (5 W)	2 A (10 W)	4 A (20 W)	6 A (30 W)	8 A (40 W)
+3.3 V	1 A (5 W)	2 A (6.6 W)	4 A (13.2 W)	6 A (19.8 W)	8 A (26.4 W)
+5VSB	1 A (5 W)	1 A (5 W)	1.5 A (7.5 W)	2 A (10 W)	2 A (10 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	78.2 W	156.4 W	233.3 W	309.6 W	392.4 W
% Max Load	19.6%	39.1%	58.3%	77.4%	98.1%
Room Temp.	44.7º C	43.9º C	44.0º C	45.5º C	47.7º C
PSU Temp.	48.0º C	47.7º C	47.5º C	48.0º C	49.6º C
Voltage Regulation	Pass	Pass	Pass	Pass	Pass
Ripple and Noise	Pass	Pass	Pass	Fail on +12 V	Fail on +12 V
AC Power	106.5 W	199.2 W	299.2 W	405.4 W	534.0 W
Efficiency	73.4%	78.5%	78.0%	76.4%	73.5%
AC Voltage	116.5 V	115.8 V	114.7 V	113.5 V	111.9 V
Power Factor	0.597	0.639	0.648	0.658	0.670
Final Result	Pass	Pass	Pass	Fail	Fail

Cooler Master eXtreme Power Plus 400 W can really deliver its labeled power at high temperatures. However, power isn’t everything.

Efficiency was always below 80%, varying between 73% and 78%.

Voltages were inside the required range. In fact during the first three tests all voltages were inside a 3% range from their nominal values. Translation: voltages closer to their nominal voltages than required, since ATX12V specification allows a 5% tolerance. During tests four and five +12 V outputs got outside this tight regulation, but they were still inside their required values.

But what really kills this unit is its very high noise and ripple levels. During tests four and five these levels surpassed the 120 mV limit on +12 V outputs, at 128.8 mV and 147.6 mV, respectively. Below you can see the results for test five. The maximum allowed is 120 mV on +12 V and 50 mV on +5 V and +3.3 V. All these numbers are peak-to-peak figures.

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Figure 16: +12VA input from load tester at 392.4 W (147.6 mV).

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Figure 17: +12VB input from load tester at 392.4 W (144.6 mV).

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Figure 18: +5 V rail with power supply delivering 392.4 W (34.4 mV).

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Figure 19: +3.3 V rail with power supply delivering 392.4 W (19.2 mV).

Since this unit was already presenting noise levels above the maximum allowed, we decided not to overload it.

Main Specifications

Cooler Master eXtreme Power Plus 400 W power supply specs include:

• ATX12V 2.3
• Nominal labeled power: 400 W.
• Measured maximum power: 392.4 W at 47.7º C.
• Labeled efficiency: Above 70%
• Measured efficiency: Between 73.4% and 78.5% at 115 V (nominal, see complete results for actual voltage).
• Active PFC: No.
• Modular Cabling System: No.
• Motherboard Power Connectors: One 20/24-pin connector and two ATX12V connectors that together form an EPS12V connector.
• Video Card Power Connectors: One six-pin connector.
• SATA Power Connectors: Four in two cables.
• Peripheral Power Connectors: Five in three cables.
• Floppy Disk Drive Power Connectors: One.
• Protections: over voltage (OVP), over current (OCP), over power (OPP) and short-circuit (SCP). Under voltage protection (UVP) present but not listed by the manufacturer.
• Warranty: Information not available.
• More Information: http://www.coolermaster.com
• Average price in the US: This product is not sold in the USA.

Conclusions

Cooler Master eXtreme Power Plus 400 W is capable to deliver its labeled power at high temperatures. But as we always like to point out, maximum power isn’t everything. This unit presents lousy efficiency and noise and ripple levels above the maximum allowed, which can lead you computer to present random behavior (“freezing,” random resets, Blue Screen of Death, etc) and overload components. Therefore we can’t recommend this product.

The three units from eXtreme Power Plus series that we’ve reviewed so far (400 W, 460 W and 500 W) are based on the same design, and the differences are that the 460 W and the 500 W models use more powerful rectifiers on the +5 V and +3.3 V outputs (the +12 V outputs from these three models use the same rectifiers). The 400 W and the 460 W models use the same switching transistors, while the 500 W model uses more powerful ones.