Enermax Liberty ECO 500 W Power Supply Review
By Gabriel Torres on January 28, 2009


Introduction

Hardware Secrets Golden Award

The new Liberty ECO series from Enermax comes to replace their popular Liberty DXX series, featuring a modular cabling system, 120 mm fan, active PFC and labeled at 40° C – i.e., the manufacturer guarantees that the unit can deliver its labeled power at this temperature. The main problem with the Liberty DXX series was efficiency, which dropped below 80% if you pulled more than 60% the unit’s maximum load. Since we had already reviewed Liberty DXX 500 W it will be really interesting to review Liberty ECO 500 W to see how this new version compares to the old version. Is Liberty ECO 500 W a good product or has the same efficiency issue as Liberty DXX 500 W? Can it really deliver 500 W? Check it out.

Enermax Liberty ECO 500 W
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Figure 1: Enermax Liberty ECO 500 W.

This power supply is small, being only 5 1/2” (140 mm) deep, featuring a 120 mm fan on its bottom and active PFC circuit, allowing Enermax to market this product in Europe. According to the manufacturer this unit has efficiency between 80% and 86% and we are going to measure this, especially because it was the main flaw with Liberty DXX series.

As mentioned Liberty ECO 500 W comes with a modular cabling system, which can be seen on the pictures below. The connectors used here are completely different from the ones used on Liberty DXX, being identical to the ones used on MODU82+ series from the same manufacturer.

Enermax Liberty ECO 500 W
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Figure 2: Enermax Liberty ECO 500 W.

The connectors used on the modular cabling system are flawed. If you pull any cable attached to the modular cabling system without pressing its lateral latches the plastic part from the connector comes off, as you can see in Figure 3. You can easily put this part back in its place, the problem is that this plastic part fits the pins in two different positions! If this happens to you, pay close attention to the other connectors to make sure to insert the plastic part using the same orientation, i.e., matching the location of the squared and trapezoidal holes with the one used by the other connectors.

Enermax Liberty ECO 500 W
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Figure 3: The plastic part from the connector comes off if you pull the cable without pressing its latches.

Enermax Liberty ECO 500 W
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Figure 4: Cables from the modular cabling system.

The motherboard cables come from inside the power supply and are protected by a nylon sleeving that also comes from inside the unit. The main motherboard cable uses a 24-pin connector and this unit comes with two ATX12V connectors that together form an EPS12V connector.

Cables for peripherals are available on the modular cabling system, and the product comes with four cables: One cable with two 6/8-pin video card auxiliary power connectors (even thought this connectors are available on the same cable, they are connected to the power supply using individual wires), one cable with three SATA power plugs, one cable with two SATA power plugs and two standard peripheral power connectors and one cable with three standard peripheral power connectors and one floppy disk drive power connector.

The number of plugs is satisfactory for a mainstream PC.

All wires are 18 AWG, which is the correct gauge to be used nowadays.

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

A Look Inside The Liberty ECO 500 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.

The first thing that caught our eye when disassembling this unit was the fan, which is the same one as used on MODU82+ and PRO82+ series from the same manufacturer: a dual-voltage fan, using a four-pin connector, which allows it to be quieter than traditional fans (this proved to be true during our tests).

The second thing we noticed was that internally Liberty ECO 500 W has nothing to do with Liberty DXX 500 W: they use completely different projects. So we were expecting to see very different results on our tests as well. Internally Liberty ECO resembles PRO82+ and MODU82+ units, but we could see enough differences between them to say that they use slightly different projects.

Enermax Liberty ECO 500 W
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Figure 5: Overall look.

Enermax Liberty ECO 500 W
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Figure 6: Overall look.

Enermax Liberty ECO 500 W
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Figure 7: 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.

This power supply is flawless on this stage, providing two extra Y capacitors and one extra ferrite coil, plus an extra X capacitor after the rectification bridge. On this power supply the MOV is located after the rectifying bridge and not before, as usual.

Enermax Liberty ECO 500 W
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Figure 8: Transient filtering stage (part 1).

Enermax Liberty ECO 500 W
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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 Liberty ECO 500 W.

Primary Analysis

On this page we will take an in-depth look at the primary stage of Liberty ECO 500 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one GBU10J rectifying bridge in its primary, which support up to 10 A at 100° C. This component is clearly overspec'ed: at 115 V this unit would be able to pull up to 1,150 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 920 W without burning this component. Of course we are only talking about this component and the real limit will depend on all other components from the power supply.

Enermax Liberty ECO 500 W
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Figure 10: Rectifying bridge.

For the active PFC circuit Liberty ECO 500 W uses two 2SK2698 power MOSFET transistors, which one capable of delivering up to 15 A in continuous mode  or up to 60 A in pulse mode, both values rated at 25° C.

The active PFC capacitor is Japanese from Hitachi and rated at 85° C.

In the switching section, another two 2SK2698 power MOSFETs are used on the traditional two-transistor forward configuration. The specs for these transistors you can read above.

Enermax Liberty ECO 500 W
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Figure 11: Two of the four power MOSFET transistors used on the primary.

The primary is controlled by a CM6802 PWM/PFC controller combo, which is a new version of the famous CM6800 that consumes less power.

Enermax Liberty ECO 500 W
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Figure 12: PWM/PFC controller.

Now let’s analyze the secondary section from Liberty ECO 500 W.

Secondary Analysis

Liberty ECO 500 W uses four Schottky rectifiers on its secondary.

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%. Of course the maximum current (and thus power) this line can really deliver will depend on other components, especially the coil.

The +12 V output is produced by two 40CPQ060 Schottky rectifiers in parallel, each one supporting up to 40 A (20 A per internal diode at 120° C). This gives us a maximum theoretical current of 57 A [(20 A x 2)/(1 – 0.30)] or 686 W for the +12 V output.

The +5 V output is produced by one STPS30L30CT Schottky rectifier, which is capable of delivering up to 30 A (15 A per internal diode at 140° C). So the maximum theoretical current the +5 V output can deliver is of 21 A [15 A/(1 – 0.30)] or 107 W.

The +3.3 V output is produced by one S30SC4M Schottky rectifier, which is capable of delivering up to 30 A (15 A per internal diode at 126° C). So the maximum theoretical current the +3.3 V output can deliver is of 21 A or 71 W.

Enermax Liberty ECO 500 W
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Figure 13: +3.3 V rectifier, +5 V rectifier and +12 V rectifier (the other +12 V rectifier is on the opposite side).

This power supply uses a PS223 monitoring integrated circuit, which is in charge of the power supply protections. This integrated circuit provides over current protection (OCP), over voltage protection (OVP), under voltage protection (UVP) and over temperature protection (OTP, not implemented on Liberty ECO series), but not over power protection (OPP). According to Enermax OPP is implemented on the primary side, through the CM6802 integrated circuit.

Enermax Liberty ECO 500 W
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Figure 14: Monitoring integrated circuit.

The electrolytic capacitors from the secondary are from CEC (manufactured in China) and labeled at 105° C, as usual.

Power Distribution

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

Enermax Liberty ECO 500 W
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Figure 15: Power supply label.

This power supply features two +12 V virtual rails distributed like this:

Now let’s see if this power supply can really deliver 500 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.

+12V1 and +12V2 are the two independent +12V inputs from our load tester and during out tests the +12V1 input was connected to the power supply +12V1 (main motherboard cable) and +12V2 (peripheral power connectors and video card auxiliary power connector) rails, while the +12V2 input was connected to the power supply +12V1 rail (EPS12V connector).

Input

Test 1

Test 2

Test 3

Test 4

Test 5

+12V1

4 A (48 W)

7 A (84 W)

11 A (132 W)

14.5 A (174 W)

18 A (216 W)

+12V2

3 A (36 W)

7 A (84 W)

10 A (120 W)

14 A (168 W)

18 A (216 W)

+5V

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

104.3 W

197.8 W

302.0 W

402.8 W

501.8 W

% Max Load

20.9%

39.6%

60.4%

80.6%

100.4%

Room Temp.

48.5° C

47.9° C

48.0° C

48.8° C

50.0° C

PSU Temp.

51.7° C

50.8° C

50.7° C

51.9° C

52.7° C

Voltage Stability

Pass

Pass

Pass

Pass

Pass

Ripple and Noise

Pass

Pass

Pass

Pass

Pass

AC Power (1)

118 W

222 W

343 W

467 W

600 W

Efficiency (1)

88.4%

89.1%

88.0%

86.3%

83.6%

AC Power (2)125.2 W233.5 W360.4 W488.4 W623.0 W
Efficiency (2)83.3%84.7%83.8%82.5%80.5%
AC Voltage111.6 V110.5 V108.8 V108.1 V106.6 V
Power Factor0.9750.9840.9870.9900.993

Final Result

Pass

Pass

Pass

Pass

Pass

Updated 06/25/2009: We re-tested this power supply using our new GWInsteak GPM-8212 power meter, which is a precision instrument and provides accuracy of 0.2% and thus presenting the correct readings for AC power and efficiency (results marked as "2" on the table above; results marked as "1" were measured with our previous power meter from Brand Electronics, which isn't so precise as you can see). We also added the numbers for AC voltage during our tests, an important number as efficiency is directly proportional to AC voltage (the higher AC voltage is, the higher efficiency is). Also, manufacturers usually announce efficiency at 230 V, which usually inflates efficiency numbers. We added power factor (PF) numbers as well. These numbers measure the efficiency of the power supply active PFC circuit. This number should be as close to 1 as possible. Under light load (20% load, i.e., 100 W), the active PFC circuit from this unit isn't as good as when operating under higher loads, but 0.975 is still a good number.

This power supply could really deliver 500 W at 50° C, which is terrific.

Enermax Liberty ECO 500 W achieved very good efficiency during our tests. If you pull up to 60% of its maximum labeled capacity (300 W) you will have at least 83% efficiency, peaking 84.7% when you pull 40% of its labeled maximum power (200 W). If you pull 80% of its labeled capacity (400 W) efficiency drops to 82.5%, still a good. At 100% load (500 W) efficiency dropped a lot, but was still above the 80% mark, at 80.5%.

So Liberty ECO series has a far better performance than the old Liberty DXX series. Enermax PRO82+ and MODU82+ series continue have an even higher efficiency, but they are more expensive.

Voltage regulation was also excellent, with all voltages within 3% from their nominal values – better than what is defined by ATX standard, which says they must be within 5% their nominal values. The exception was -12 V, which was however still within 5% from its nominal value (the tolerance for this particular output is 10%).

Noise and ripple levels were another highlight from this product, achieving values far below the maximum allowed – noise level at +12 V outputs was only at ¼ of the maximum allowed, while noise level at +5 V and +3.3 V was less than 2/5 the maximum allowed. Below you can see the noise and ripple levels during test number five, when the unit was delivering 501.8 W. Just to remember, the maximum allowed is 120 mV for the 12 V outputs and 50 mV for +5 V and +3.3 V outputs. All values are peak-to-peak.

Enermax Liberty ECO 500 W
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Figure 16: Noise level at +12V1 with the reviewed power supply delivering 501.8 W (34 mV).

Enermax Liberty ECO 500 W
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Figure 17: Noise level at +12V2 with the reviewed power supply delivering 501.8 W (34.4 mV).

Enermax Liberty ECO 500 W
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Figure 18: Noise level at +5 V with the reviewed power supply delivering 501.8 W (19.6 mV).

Enermax Liberty ECO 500 W
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Figure 19: Noise level at +3.3 V with the reviewed power supply delivering 501.8 W (14.6 mV).

Now let’s see if we can pull even more power from Liberty ECO 500 W.

Overload Tests

Before overloading power supplies we always test first if the over current protection (OCP) circuit is active and at what level it is configured. For this test we installed only cables that were connected to the unit’s +12V1 rail (main motherboard cable and EPS12V cable), turned the unit on with the pattern for our test number five and increased current at +12V1 until we saw the unit shutting down. This happened when we tried to pull more than 32 A. We think this value is too high, especially when the label says that the limit for each +12 V rail if of 24 A. We prefer to see OCP configured at a level closer to what is printed on the label.

We could easily overload this unit. The problem was that if we tried to pull more than what is describe in the table below, ripple jumped through the roof. Pulling even more the unit wouldn’t turn on, which is great (probably the OVP or UVP in action, as the oscillation at the output was too big).

Below you can see the maximum amount of current/power we could pull from this unit. Noise level was still well within specs, at only 50 mV on both +12V1 and +12V2 inputs.

Input

Maximum

+12V1

21 A (252 W)

+12V2

21 A (252 W)

+5V

6 A (30 W)

+3.3 V

6 A (19.8 W)

+5VSB

2.5 A (12.5 W)

-12 V

0.5 A (6 W)

Total

572 W

% Max Load

114.4%

Room Temp.

52.2° C

PSU Temp.

55.9° C

AC Power (1)

690 W

Efficiency (1)

82.9%

AC Power (2)724.0 W
Efficiency (2)79.0%
AC Voltage106.1 V
Power Factor0.994

With Enermax Liberty ECO 500 W delivering more than 500 W efficiency dropped below the 80% mark (consider the results marked as "2", as they are the correct ones, measured with our precision power meter).

Main Specifications

Enermax Liberty ECO 500 W power supply specs include:

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

Conclusions

We were really impressed by Enermax Liberty ECO 500 W, and it is always good to see a manufacturer improving their product line. Liberty ECO series has absolutely nothing to do with the previous Liberty DXX series: it uses a completely different internal design that provides a far higher efficiency.

Everything is perfect on Liberty ECO 500 W: high efficiency (between 83% and 85% if you pull up to 300 W; pulling 400 W you will see 82.5% efficiency; and at full load efficiency drops to 80.5%, but definetely this product wasn't developed to work full time delivering 500 W), very low noise and ripple levels, right number of cables for the mainstream user and excellent price (USD 100 at Newegg.com).

The only reason we would recommend someone to buy a different product is if you need even more cables or if you want a product with an even higher efficiency. In this case, however, there is no other option but looking for a more expensive product.

Originally at http://www.hardwaresecrets.com/article/Enermax-Liberty-ECO-500-W-Power-Supply-Review/688


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