AcBel Polytech iPower 660 Power Supply Review
By Gabriel Torres on May 13, 2008


Introduction

AcBel Polytech is a very well known OEM manufacturer, producing power supplies for brands such as Cooler Master. Now they seem interested in the retail market and today we are going to completely dissect their iPower 660 model (also known as PS2/660 or PC7016), which should reach the US market pretty soon, to see if it can really deliver its labeled power and what is its internal design.

The first thing we noticed about this power supply is that it isn’t a 660 W model as everyone would assume. See how AcBel used the name “iPower 660” without adding the letter “W” for “watts.” According to the power supply label and to AcBel’s website, iPower 660 is a 610 W power supply with 660 W peak power. So why not labeling it iPower 610 W instead? We simply hate manufacturers that use deceitful naming systems and we honestly think that manufacturers that do such kind of thing should be sued. Because of this we will have to make our tests assuming that this is a 610 W unit, but we will also check if it can deliver 660 W. If this power supply can’t deliver 660 W we honestly hope that the US distributor change its name to reflect its real power capability. We will talk more about this later, after we’ve done our testings.

AcBel iPower 660
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Figure 1: AcBel Polytech iPower 660 power supply.

AcBel iPower 660
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Figure 2: AcBel Polytech iPower 660 power supply.

As it is becoming the new standard, this power supply uses a big 120 mm fan on its bottom (the power supply is upside down on Figures 1 and 2) and a big mesh on the rear side where traditionally we had an 80 mm fan. We like this design as it provides not only a better airflow but the power supply produces less noise, as the fan can rotate at a lower speed in order to produce the same airflow as an 80 mm fan.

This power supply has active PFC, which provides a better usage of the power grid and allowing Acbel Polytech to sell this product in Europe (read more about PFC on our Power Supply Tutorial). AcBel says that this product has 80% efficiency. The higher the efficiency the better – an 80% efficiency means that 80% of the power pulled from the power grid will be converted in power on the power supply outputs and only 20% will be wasted. This translates into less consumption from the power grid (as less power needs to be pulled in order to generate the same amount of power on its outputs), meaning lower electricity bills.

The main motherboard cable uses a 20/24-pin connector and this power supply has two ATX12V connectors that together form an EPS12V connector.

This power supply comes with five peripheral power cables: two 6-pin auxiliary power cables for video cards, two cables containing two standard peripheral power connectors and two SATA power connectors and one cable with three standard power connectors and one floppy disk drive power connector.

The number of connectors provided by this power supply is adequate for a mainstream user, but high-end users would need more connectors, especially more SATA power plugs.

On this power supply all wires are 20 AWG, except the ones used with the two ATX12V connectors, which are 18 AWG. This is ridiculous for a power supply on this power range; all wires should be 18 AWG, especially the ones used on the auxiliary power cables for video cards. On the other hand each video card 6-pin power plug is attached to an individual cable, while on several mainstream power supplies these connectors share the same cable.

On the aesthetic side AcBel Polytech used nylon sleevings on all cables, but they don’t come from inside the power supply housing.

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

A Look Inside The iPower 660

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, and then in the following pages we will discuss in detail the quality and ratings of the components used.

AcBel iPower 660
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Figure 3: Overall look.

AcBel iPower 660
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Figure 4: Overall look.

AcBel iPower 660
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Figure 5: 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.

On this stage this power supply is flawless, providing two extra Y capacitors, one extra X capacitor and a ferrite bead attached to the main AC cable. This power supply also provides an X capacitor after the rectifying bridges.

AcBel iPower 660
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Figure 6: Transient filtering stage (part 1).

AcBel iPower 660
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Figure 7: Transient filtering stage (part 2).

In the next page we will have a more detailed discussion about the components used in the iPower 660.

Primary Analysis

On this page we will take an in-depth look at the primary stage of AcBel Polytech iPoer 660. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses two GBU605 rectifying bridges connected in parallel in its primary, each one supporting up to 6 A at 100° C, so the rectifying section can handle up to 12 A at 100° C. The bridges aren’t attached to a heatsink. This section is clearly overspec'ed: at 115 V this unit would be able to pull up to 1,380 W from the power grid; assuming 80% efficiency, the bridges would allow this unit to deliver up to 1,104 W without burning them. Of course we are only talking about this component and the real limit will depend on all other components from the power supply. Of course the lack of a heatsink would limit this maximum current.

AcBel iPower 660
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Figure 8: Rectifying bridges.

The active PFC circuit uses two FCPF11N60 power MOSFET transistors, which one capable of handling up to 7 A in continuous mode at 100° C (or 11 A at 25° C; see the difference temperature makes) or 33 A in pulse mode at 25° C. These transistors are located on the same heatsink as the switching transistors.

On the switching section this power supply uses another two FCPF11N60 power MOSFET transistors in the traditional two-transistor forward configuration.

AcBel iPower 660
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Figure 9: Active PFC transistor (left) and switching transistor (right).

The primary section of this power supply is controlled by a FAN4800 integrated circuit, which is a PFC/PWM controller combo.

AcBel iPower 660
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Figure 10: Active PFC/PWM controller combo.

Secondary Analysis

This power supply has four Schottky rectifiers on its secondary.

The +12 V output is produced by three STPS20S100CT Schottky rectifiers connected in parallel, each one supporting up to 20 A at 150° C (10 A per internal diode). The maximum theoretical current the +12 V 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 (which in this case is made by three 10 A diodes in parallel). Just as an exercise, we can assume a typical duty cycle of 30%. This would give us a maximum theoretical current of 43 A or 514 W for the +12 V output. The maximum current this line can really deliver will depend on other components, in particular the coil used. Usually good power supplies have this section overspec'ed, which isn't the case with this power supply. We think the manufacturer should have given more headroom here (the maximum teoretical value is too low, probably indicating that this unit won't be able to deliver its labeled power; let's see what really happens later when we pull its full power). This situation is complicated by the fact that the +3.3 V output in generated from the +12 V output (more on this later).

The +5 V output is produced by one SBR30A40CT Schottky rectifier, which supports up to 30 A at 110° C (15 A per internal diode). The maximum theoretical current the +5 V 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 (which in this case is made by one 15 A diodes in parallel). Just as an exercise, we can assume a typical duty cycle of 30%. This would give us a maximum theoretical current of 21 A or 107 W for the +5 V output. The maximum current this line can really deliver will depend on other components, in particular the coil used. Here we think that the current/power limit is too low as well.

If you add both maximum theoretical values we calculated (514 W + 107 W) we have 621 W. Based on the components used on this power supply we don't believe that it can deliver its labeled power. But let's wait and see what happens when we put this unit on our load tester.

This power supply uses a voltage regulator integrated circuit for regulating the -12 V output (7912). This is a great option for producing this output, as it produces a more stable -12 V output.

AcBel iPower 660
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Figure 11: +12 V rectifiers.

AcBel iPower 660
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Figure 12: -12 V voltage regulator, +12 V rectifier and +5 V rectifier.

If you are following us you may have noticed that the +3.3 V rectifier is missing. This power supply uses an exotic configuration, where the +3.3 V output is achieved through a voltage regulator circuit connected to the +12 V output. Since the +3.3 V outputs are being generated using the +12 V rectifiers, the amount of current (and thus power) the +3.3 V and +12 V outputs can pull at the same time are limited by the maximum capacity of these rectifiers. This voltage regulator is located on a small printed circuit board, as you can see in Figure 13.

AcBel iPower 660
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Figure 13: +3.3 V voltage regulator.

This power supply uses a WT7527 monitoring integrated circuit, which is in charge of the power supply protections, like OCP (over current protection). Unfortunately there is no datasheet for this component on the manufacturer’s website, so we couldn’t check what protections it really supports. Analyzing the printed circuit board from the reviewed power supply we could clearly see each +12 V virtual rail connected to this integrated circuit. OCP was really activated, as we will talk about later.

AcBel iPower 660
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Figure 14: WT7527 monitoring integrated circuit.

The thermal sensor is attached to the secondary heatsink and you can see it in Figure 12. This sensor is used to control the fan speed according to the power supply internal temperature.

This power supply uses Chinese electrolytic capacitors rated at 85° C from Aishi on the active PFC circuit and Taiwanese capacitors from OST and Ltec rated at 105° C on the secondary.

Power Distribution

In Figure 15, you can see the power supply label containing all the power specs. You can clearly see that the manufacturer says that the maximum power this unit can deliver is 610 W (591.5 W + 18.5 W), not 660 W. Pay also attention as the “660” on the top right corner does not have a “W” after it.

AcBel iPower 660
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Figure 15: Power supply label.

As you can see this power supply has three +12 V virtual rails, distributed like this:

We think that this distribution is adequate, but AcBel should have labeled the video card power connector that is connected to the +12V3 rail with a label to indicate that this the main and preferred cable for you to connect your video card, if you have just one video card on your system.

Now let’s see if this power supply can really deliver 610 W of power.

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 610 W maximum capacity (actual percentage used listed under “% Max Load”) – and not 660 W –, 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.

+12V2 is the second +12V input from our load tester and during our tests we connected the two power supply ATX12V connectors to it. So it was connected to the power supply +12V2 bus. The +12V1 input from our load tester, on the other hand, was connected to both +12V1 (main motherboard connector and peripheral connectors) and +12V3 (video card power plug) rails.

Input

Test 1

Test 2

Test 3

Test 4

Test 5

+12V1

4.5 A (54 W)

9.5 A (114 W)

14 A (168 W)

18 A (216 W)

23 A (276 W)

+12V2

4.5 A (54 W)

9 A (108 W)

14 A (168 W)

18 A (216 W)

22 A (264 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 (3.3 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)

2.5 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

126.9 W

247.5 W

378.2 W

491. W

613.7 W

% Max Load

20.8%

40.6%

62.0%

80.5%

100.6%

Room Temp.

43.6° C

45.2° C

46.1° C

46.1° C

46.1° C

PSU Temp.

50.9° C

50.1° C

50.4° C

50.4° C

50.4° C

Voltage Stability

Pass

Pass

Pass

Pass

Pass

Ripple and Noise

Pass

Pass

Pass

Pass

Pass

AC Power

153 W

293 W

457 W

601 W

773 W

Efficiency

82.9%

84.5%

82.8%

81.7%

79.4%

Final Result

Pass

Pass

Fail

Fail

Fail

Just to remember, we are assuming that this is a 610 W power supply and we tested it as such.

The main problem with this power supply is that it can’t work continuously at a room temperature of 45° C. During our test number three the power supply shut down after 3 minutes, during test number four the power supply shut down after 10 seconds and during test number five the power supply shut down after 5 seconds. Well, at least it’s over power protection (OPP) was clearly in action.

iPower 660 is a textbook example of a power supply which was labeled at 25° C, which is a temperature impossible to be achieved inside a computer.

We also have seen that the rectifiers used on this power supply didn't provide enough current for this unit to be able to deliver the unit's labeled power, and our theoretical calculations proved to true.

We let our load tester and power supply cool down and turned them back on with pattern number four. The power supply could only stay on for two minutes – it shut down when the room temperature achieved 40° C.

So even though its power supply can in theory deliver up to 610 W, in practical terms this doesn’t happen. This unit can’t continuously deliver more than 350 W at a room temperature of 45° C.

Voltage regulation was  outstanding and during all our tests all outputs were within 3% of their nominal voltages – ATX specification defines that all outputs must be within 5% of their nominal voltages (10% for -12 V) –, including -12 V, which usually is not close to its nominal value.

Efficiency was good, but dropped below 80% during the five seconds we could run test number five.

Even though during all tests ripple and noise levels were within specs, they were almost touching the limit. With this power supply delivering 610 W noise level at +12V1 input from our load tester was at 98.9 mV, at +12V2 noise was at 95.2 mV, at +5 V it was at 25.8 mV and at +3.3 V it was at 15.2 mV.  Just to remember, all values are peak-to-peak voltages and the maximum allowed set by ATX standard is 120 mV for +12 V and 50 mV for +5 V and +3.3 V.

AcBel iPower 660
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Figure 16: Noise at +12V1 input from load tester at 610 W.

AcBel iPower 660
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Figure 17: Noise at +12V2 input from load tester at 610 W.

AcBel iPower 660
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Figure 18: Noise at +5 V input from load tester at 610 W.

AcBel iPower 660
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Figure 19: Noise at +3.3 V input from load tester at 610 W.

Over current protection (OCP) circuit was active and shutting down the power supply whenever we tried to pull more than 21 A from any +12 V rail.

Short circuit protection (SCP) worked fine for both +5 V and +12 V lines.

Main Specifications

AcBel Polytech iPower 660 power supply specs include:

Conclusions

How do you call a 610 W power supply that is labeled as a 660 W product but can only deliver half of this continuously at a room temperature of 45° C and will reach the market costing between USD 120 and USD 130? Because the word we have for that is unpublishable.

The funny thing is that Cooler Master eXtreme Power Plus 460 W – which is also manufactured by AcBel Polytech – costs only USD 40 and is a better product than iPower 660.

AcBel Polytech iPower 660 is a textbook example of a power supply that was labeled at 25° C. The problem is that no computer in the world works internally at such low temperature and semiconductors lose their capability of delivering current as the temperature increases, a phenomenon called de-rating.

Some people think that as long as a power supply can meet the manufacturer’s published specs it is a good product. This is a perfect example of why we disagree with this mentality: what’s the use of a 610 W power supply than can’t deliver enough power to your system when it is hot?

The only good thing we could say about this power supply that it could be worse: it could have exploded or burned, but at least over current and over power protections are working fine.

If you are looking for a good power supply on the 600 W range there are several good options on the market, with OCZ StealthXStream 600 W providing the best cost/benefit ratio among the models we’ve reviewed so far. If you are a mainstream user maybe you don’t even really need 600 W and a good power supply like Antec EarthWatts 500 W, Corsair VX450W or SilverStone Strider ST50F 500 W should be enough if you are looking for a product with good cost/benefit ratio.

Our conclusion is pretty obvious: stay away from this power supply!

Originally at http://www.hardwaresecrets.com/article/AcBel-Polytech-iPower-660-Power-Supply-Review/552


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