Cooler Master GX 450 W Power Supply Review
By Gabriel Torres on March 29, 2011


Introduction

Hardware Secrets Silver Award

The Cooler Master GX power supply series was released a while ago with 550 W, 650 W, and 750 W models. Now the manufacturer is releasing a 450 W version. Let’s see if it is a good buy.

It is important to understand that while the other GX models are manufactured by Seventeam (relabeled PWL series units), the GX 450 W is manufactured by Enhance Electronics and is internally identical to the BFG LS-450 (except for the active PFC transistor).

Cooler Master GX 450 W power supply
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Figure 1: Cooler Master GX 450 W power supply

Cooler Master GX 450 W power supply
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Figure 2: Cooler Master GX 450 W power supply

The Cooler Master GX 450 W is 6.3” (160 mm) deep, using a 120 mm fan on its bottom. This fan is an ADDA AD1212MS-A71GL, which is a sleeve bearing fan with a maximum rotation of 2,050 rpm and a maximum airflow of 80.5 cfm.

This unit features active PFC, of course, and doesn’t come with a modular cabling system. The cables are protected with nylon sleeves and the unit comes with the following cables and connectors:

All wires are 18 AWG, except the +3.3 V, +5 V and +12 V wires on the main motherboard cable, which are thicker (16 AWG).

The cable configuration is compatible with a mainstream 450 W product, with only one video card power connector and a reduced number of peripheral power connectors. We wish there were more space between the SATA connectors.

Cooler Master GX 450 W power supply
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Figure 3: Cables

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

A Look Inside the Cooler Master GX 450 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.

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. The printed circuit board of the GX 450 W is completely different from the one used on the other GX models and, as mentioned, it is identical to the BFG LS-450, which is not manufactured anymore.

Cooler Master GX 450 W power supply
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Figure 4: Top view

Cooler Master GX 450 W power supply
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Figure 5: Front quarter view

Cooler Master GX 450 W power supply
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Figure 6: Rear quarter view

Cooler Master GX 450 W power supply
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Figure 7: The printed circuit board

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 power supply, this stage is flawless. It has two X capacitors and two Y capacitors more than the minimum required.

Cooler Master GX 450 W power supply
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Figure 8: Transient filtering stage (part 1)

Cooler Master GX 450 W power supply
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Figure 9: Transient filtering stage (part 2)

In the next page we will have a more detailed discussion about the components used in the Cooler Master GX 450 W.

Primary Analysis

On this page we will take an in-depth look at the primary stage of the Cooler Master GX 450 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one GBU806 rectifying bridge on its primary, which is attached to an individual heatsink. This component 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 736 W without burning itself out. Of course, we are only talking about this component, and the real limit will depend on all the other components in this power supply.

Cooler Master GX 450 W power supply
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Figure 10: Rectifying bridge

The active PFC circuit uses only one transistor, an IPW50R140CP, which supports up to 23 A at 25° C or up to 15 A at 100° C (note the difference temperature makes) in continuous mode, or up to 56 A in pulse mode at 25° C. This transistor presents a 140 mΩ resistance when turned on, a characteristic called RDS(on). The lower this number the better, meaning that the transistor will waste less power and the power supply will have a higher efficiency. The BFG LS-450 used a more powerful transistor here (32 A at 25° C or 20 A at 100° C).

The electrolytic capacitor that filters the output of the active PFC circuit is Japanese, from Matsushita (Panasonic), and labeled at 105° C.

In the switching section, two STP12NM50 MOSFETs are used in the traditional two-transistor forward configuration. Each one supports up to 12 A at 25° C or up to 7.5 A at 100° C in continuous mode, or up to 48 A at 25° C in pulse mode, with an RDS(on) of 350 mΩ.

Cooler Master GX 450 W power supply
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Figure 11: One of the switching transistors, active PFC diode, and active PFC transistor

The primary is controlled by a CM6806 active PFC/PWM combo.

Cooler Master GX 450 W power supply
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Figure 12: Active PFC/PWM combo controller

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

Secondary Analysis

The Cooler Master GX 450 W has four Schottky rectifiers attached to its secondary heatsink.

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. As an exercise, we can assume a duty cycle of 30%.

The +12 V output uses one STPS30L60CW Schottky rectifier for its direct rectification (30 A, 15 A per internal diode at 130° C, 0.75 V maximum voltage drop) and one 40CPQ060 Schottky rectifier for the “freewheeling” part of the rectification (40 A, 20 A per internal diode at 120° C, 0.68 V maximum voltage drop). This gives us a maximum theoretical current of 43 A or 514 W for the +12 V output.

The +5 V output uses one STPS30L40CW Schottky rectifier (30 A, 15 A per internal diode at 135° C, 0.74 V maximum voltage drop), giving us a maximum theoretical current of 21 A or 107 W for the +5 V output.

The +3.3 V output uses one STPS40L45CW Schottky rectifier (40 A, 20 A per internal diode at 130° C, 0.7 V maximum voltage drop), giving us a maximum theoretical current of 29 A or 94 W for the +3.3 V output.

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.

Cooler Master GX 450 W power supply
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Figure 13: +3.3 V, +5 V and +12 V rectifiers

This power supply uses a PS223 monitoring integrated circuit, which supports over voltage (OVP), under voltage (UVP), over temperature (OTP), and over current (OCP) protections. The over current protection circuit available in this integrated circuit has four channels, one for +3.3 V, one for +5 V, and two for +12 V. However, in this power supply only one +12 V OCP channel is used, as it has a single-rail design.

Cooler Master GX 450 W power supply
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Figure 14: Monitoring circuit

The electrolytic capacitors available in the secondary are from Teapo and labeled at 105° C.

Power Distribution

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

Cooler Master GX 450 W power supply
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Figure 15: Power supply label

This power supply has a single +12 V rail, so there is not much to talk about here.

Let’s now see if this power supply can really deliver 450 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 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 were connected to the power supply single +12 V rail (the EPS12V connector was installed on the +12VB input).

Input

Test 1

Test 2

Test 3

Test 4

Test 5

+12VA

3 A (36 W)

6.5 A (78 W)

9.5 A (114 W)

13 A (156 W)

16 A (192 W)

+12VB

3 A (36 W)

6.5 A (78 W)

9.5 A (114 W)

13 A (156 W)

16 A (192 W)

+5V

1 A (5 W)

2 A (10 W)

4 A (20 W)

5 A (25 W)

7 A (35 W)

+3.3 V

1 A (3.3 W)

2 A (6.6 W)

4 A (13.2 W)

5 A (16.5 W)

7 A (23.1 W)

+5VSB

1 A (5 W)

1 A (5 W)

1 A (5 W)

1.5 A (7.5 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

89.4 W

180.3 W

268.9 W

361.3 W

450.1 W

% Max Load

19.9%

40.1%

59.8%

80.3%

100.0%

Room Temp.

44.4° C

45.2° C

45.5° C

46.2° C

46.4° C

PSU Temp.

45.2° C

45.3° C

45.8° C

45.9° C

46.2° C

Voltage Stability

Pass

Pass

Pass

Pass

Pass

Ripple and Noise

Pass

Pass

Pass

Pass

Pass

AC Power

105.1 W

208.4 W

314.0 W

430.7 W

553.3 W

Efficiency

85.1%

86.5%

85.6%

83.9%

81.3%

AC Voltage

117.7 V

117.5 V

117.2 V

115.7 V

114.4 V

Power Factor

0.927

0.940

0.954

0.964

0.978

Final Result

Pass

Pass

Pass

Pass

Pass

The Cooler Master GX 450 W can really deliver its labeled wattage at high temperatures. During our test five, however, the unit shut down from time to time due to its over temperature protection kicking in (this protection was available, as we could clearly see by the presence of two thermal sensors, one for this circuit and one for the fan circuit).

Efficiency was high, between 81.3% and 86.5%, which was a great surprise since this unit has only the standard 80 Plus certification.

Voltage regulation was very good, with all positive voltages within 3% of their nominal values, except for the +5 V output during test one (but it was still inside the proper range; the -12 V output was outside this tighter regulation but was still inside the proper range as well). This means that voltages were closer to their nominal values than required by the ATX12V specification, which says positive voltages must be within 5% of their nominal values and negative voltages must be within 10% of their nominal values.

Noise and ripple levels were always below the maximum allowed. At +5 V and +3.3 V they were extremely low, while on +12 V they were above what we’d like to see to consider this unit impeccable but still below the maximum allowed. Below you can see the results for the power supply outputs during test number five. The maximum allowed is 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.

Cooler Master GX 450 W power supply
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Figure 16: +12VA input from load tester during test five at 450.1 W (81.6 mV)

Cooler Master GX 450 W power supply
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Figure 17: +12VB input from load tester during test five at 450.1 W (74.2 mV)

Cooler Master GX 450 W power supply
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Figure 18: +5V rail during test five at 450.1 W (12.2 mV)

Cooler Master GX 450 W power supply
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Figure 19: +3.3 V rail during test five at 450.1 W (7.4 mV)

If we tried to pull more than 450 W the unit would immediately shut down.

Main Specifications

The specs of the Cooler Master GX 450 W include:

Conclusions

The Cooler Master GX 450 W is a good mainstream power supply, with high efficiency (between 81.3% and 86.4%), very good voltage regulation, and low noise and ripple levels.

It is very important to understand that the 450 W model uses a completely different internal design compared to the more powerful models from the GX series.

The fact that the over temperature protection kicked in during our full load test can be seen as a good thing or as a bad thing. On the good side, we know the unit has this protection and it is working. On the bad side, this probably means that the secondary heatsink is under-dimensioned and/or the over temperature protection is set to trigger at a value that is too low.

The fact that we couldn’t pull more than 450 W from is also a double-edged sword. Some users will like that the unit has its protections working at a tight configuration, while others would prefer that the unit had some margin for overloading.

At a suggested price of only USD 50 – with stores probably offering less than that – the Cooler Master GX 450 W comes with an excellent cost/benefit ratio for users that want an inexpensive yet safe power supply with high efficiency.

Originally at http://www.hardwaresecrets.com/article/Cooler-Master-GX-450-W-Power-Supply-Review/1234


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