OCZ ZX Series 850 W Power Supply Review
By Gabriel Torres on February 22, 2011


Introduction

Hardware Secrets Golden Award

The new OCZ ZX Series comes to replace the Z Series from the same manufacturer. Three models are being offered so far: 850 W, 1,000 W and 1,250 W, all with a full modular cabling system, 80 Plus Gold certification, single +12 V rail, and synchronous design with DC-DC conversion. Let’s see if the 850 W model is a good buy.

This power supply is manufactured by an obscure Chinese company called Great Wall, being the model GW-EPS850DA(90+) from this company. This unit is also sold as Sparkle SCC-850AF (the unit sold under Sparkle brand does not offer a full modular cabling system, though – the main motherboard cable and the ATX12V/EPS12V cables are permanently attached to the power supply). Diablotek will also release a power supply based on the same unit, the PDAX-850GW.

OCZ ZX Series 850 W power supply
click to enlarge
Figure 1: OCZ ZX Series 850 W power supply

OCZ ZX Series 850 W power supply
click to enlarge
Figure 2: OCZ ZX Series 850 W power supply

The OCZ ZX Series 850 W is 6.9” (175 mm) deep, with a 140 mm ball bearing fan (Yate Loon D14BH-12, 2,800 rpm, 140 cfm) on its bottom part.

The new OCZ ZX Series 850 W has a fully modular cabling system, meaning that even the main motherboard cable is modular. This system has 12 connectors and the power supply comes with the following cables:

The cables with SATA and peripheral power connectors use 18 AWG wires, but the main motherboard cable, the EPS12V/ATX12V cables and the video card cables use thicker 16 AWG wires, which is always nice to see.

The number of SATA cables is fantastic (12), but it would be better if this unit had six video card power connectors instead of only four, this way you could install three high-end video cards without needing to use adapters.

OCZ ZX Series 850 W power supply
click to enlarge
Figure 3: Cables

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

A Look Inside The OCZ ZX Series 850 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, and then in the following pages we will discuss in detail the quality and ratings of the components used.

OCZ ZX Series 850 W power supply
click to enlarge
Figure 4: Top view

OCZ ZX Series 850 W power supply
click to enlarge
Figure 5: Front quarter view

OCZ ZX Series 850 W power supply
click to enlarge
Figure 6: Rear quarter view

OCZ ZX Series 850 W power supply
click to enlarge
Figure 7: 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. 

Although the OCZ ZX Series 850 W has two ferrite coils, two X capacitors, and two Y capacitors more than the minimum required, it doesn’t come with an MOV, component in charge of removing spikes coming from the power grid. This is certainly a flaw on a high-end product.

OCZ ZX Series 850 W power supply
click to enlarge
Figure 8: Transient filtering stage (part 1)

OCZ ZX Series 850 W power supply
click to enlarge
Figure 9: Transient filtering stage (part 2)

In the next page we will have a more detailed discussion about the components used in the OCZ ZX Series 850 W.

Primary Analysis

On this page we will take an in-depth look at the primary stage of the OCZ ZX Series 850 W For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses two US8K80R rectifying bridges in parallel, which are attached to the same heatsink used by the active PFC and switching transistors. Each bridge supports up to 8 A at 108° C so, in theory, you would be able to pull up to 1,840 W from a 115 V power grid. Assuming 80% efficiency, the bridges would allow this unit to deliver up to 1,472 W without burning themselves out. Of course, we are only talking about these components, and the real limit will depend on all the other components in this power supply.

OCZ ZX Series 850 W power supply
click to enlarge
Figure 10: Rectifying bridges

The active PFC circuit uses three SPW20N60C3 MOSFETs, each one capable of delivering up to 20.7 A at 25° C or up to 13.1 A at 100° C (note the difference temperature makes) in continuous mode, or up to 62.1 A in pulse mode at 25° C. These transistors present a 190 mΩ resistance when turned on, a characteristic called RDS(on). The lower this number the better, meaning that the transistors will waste less power and the power supply will achieve a higher efficiency.

OCZ ZX Series 850 W power supply
click to enlarge
Figure 11: Active PFC transistors

This power supply uses two electrolytic capacitors to filter the output from the active PFC circuit. The use of more than one capacitor here has absolute nothing to do with the “quality” of the power supply, as laypersons may assume (including people without the proper background in electronics doing power supply reviews around the web). Instead of using one big capacitor manufacturers may choose to use two or more smaller components that will give the same total capacitance, in order to better accommodate components on the printed circuit board, as capacitors with lower capacitance are physically smaller than capacitors with higher capacitance. The ZX Series 850 W uses two 330 µF x 420 V capacitor connected in parallel; this is equivalent of one 660 µF x 420 V capacitor. These capacitors are from CapXon and are labeled at 105° C.

In the switching section, another two SPW20N60C3 MOSFET transistors are used, installed in the traditional two-transistor forward configuration. The specs for these transistors are published above.

OCZ ZX Series 850 W power supply
click to enlarge
Figure 12: Active PFC diode and switching transistors

The primary is managed by a CM6802 active PFC/PWM combo controller.

OCZ ZX Series 850 W power supply
click to enlarge
Figure 13: Active PFC/PWM controller

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

Secondary Analysis

This power supply uses a synchronous design in its secondary, meaning that the Schottky rectifiers were replaced by MOSFET transistors in order to increase efficiency. On top of that, this unit uses a DC-DC design, meaning that this unit is basically a +12 V power supply, with the +5 V and +3.3 V outputs being generated by two small power supplies attached to the +12 V output.

The +12 V output is rectified by four IPP034NE7N3 MOSFETs, each one capable of handling up to 100 A at 100° C in continuous mode or up to 400 A at 25° C in pulse mode, with an RDS(on) of only 3.4 mΩ. This would give a maximum theoretical current of 286 A or 3,429 W for the +12 V rail.

OCZ ZX Series 850 W power supply
click to enlarge
Figure 14: Two of the four +12 V transistors and +5VSB rectifier

As already explained, the +5 V and +3.3 V outputs are obtained by installing two smaller switch-mode power supplies to the +12 V output, each one available on an individual daughterboard. Each converter is managed by an APW7073 PWM controller, and uses four IPD060N03L MOSFETs, each one capable of handling up to 50 A at 100° C in continuous mode, or 350 A at 25° in pulse mode, with an RDS(on) of only 6 mΩ.

OCZ ZX Series 850 W power supply
click to enlarge
Figure 15: One of the DC-DC converters

OCZ ZX Series 850 W power supply
click to enlarge
Figure 16: One of the DC-DC converters

The secondary is monitored by a PS223 integrated circuit. This chip supports OCP (over current protection), over voltage protection (OVP), under voltage protection (UVP) and over temperature protection (OTP). This circuit has four OCP channels (+3.3 V, +5 V and two +12 V), but the manufacturer decided to use only one for the +12 V output, making this power supply a single-rail unit.

OCZ ZX Series 850 W power supply
click to enlarge
Figure 17: Monitoring circuit

Power Distribution

In Figure 18, you can see the power supply label containing all the power specs.

OCZ ZX Series 850 W power supply
click to enlarge
Figure 18: 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 850 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 our tests, both were connected to the power supply single +12 V rail (the EPS12V connector was installed on the +12VB input of our load tester).

Input

Test 1

Test 2

Test 3

Test 4

Test 5

+12VA

6 A (72 W)

13 A (156 W)

18.5 A (222 W)

25 A (300 W)

31 A (372 W)

+12VB

6 A (72 W)

12 A (144 W)

18.5 A (222 W)

25 A (300 W)

31 A (372 W)

+5V

2 A (10 W)

4 A (20 W)

6 A (30 W)

8 A (40 W)

10 A (50 W)

+3.3 V

2 A (6.6 W)

4 A (13.2 W)

6 A (19.8 W)

8 A (26.4 W)

10 A (33 W)

+5VSB

1 A (5 W)

1.5 A (7.5 W)

2 A (10 W)

2.5 A (12.5 W)

3 A (15 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

173.9 W

350.4 W

512.6 W

685.9 W

845.8 W

% Max Load

20.5%

41.2%

60.3%

80.7%

99.5%

Room Temp.

45.4° C

45.0° C

46.1° C

48.0° C

46.8° C

PSU Temp.

44.6° C

44.5° C

46.0° C

48.4° C

52.8° C

Voltage Regulation

Pass

Pass

Pass

Pass

Pass

Ripple and Noise

Pass

Pass

Pass

Pass

Pass

AC Power

197.6 W

389.4 W

574.2 W

778.0 W

978.0 W

Efficiency

88.0%

90.0%

89.3%

88.2%

86.5%

AC Voltage

117.8 V

115.1 V

112.5 V

110.4 V

108.4 V

Power Factor

0.972

0.990

0.995

0.997

0.998

Final Result

Pass

Pass

Pass

Pass

Pass

The OCZ ZX Series 850 W can really deliver its labeled wattage at high temperatures.

Efficiency was very high, between 86.5% and 90.0%. Unfortunately this unit can’t hold 87% efficiency during full load (850 W) at high temperatures, even though the 80 Plus Gold certification promises 87% minimum at full load. This happened because Ecos Consulting (the company behind the 80 Plus certification) tests power supplies at only 23° C, and we test power supplies between 45° C and 50° C, and efficiency drops with temperature. But 86.5% is far from being a “bad” result.

Voltage regulation was another highlight of this product, with all voltages within 3% of their nominal values – except the -12 V output during tests one and two, but still inside the allowed range. The ATX12V specification allows voltages to be up to 5% from their nominal values (10% for the -12 V output). Therefore this power supply presents its main voltages closer to their nominal values than necessary.

Noise and ripple levels were always extremely low on the +5 V and +3.3 V outputs, and low enough on the +12 V outputs. Below you can see the results for the power supply outputs during test number five. The maximum allowed is 120 mV for the +12 V and -12 V outputs, and 50 mV for the +5 V, +3.3 V, and +5VSB outputs. All values are peak-to-peak figures.

OCZ ZX Series 850 W power supply
click to enlarge
Figure 19: +12VA input from load tester during test five at 845.8 W (57.4 mV)

OCZ ZX Series 850 W power supply
click to enlarge
Figure 20: +12VB input from load tester during test five at 845.8 W (58.4 mV)

OCZ ZX Series 850 W power supply
click to enlarge
Figure 21: +5V rail during test five at 845.8 W (8.6 mV)

OCZ ZX Series 850 W power supply
click to enlarge
Figure 22: +3.3 V rail during test five at 845.8 W (9.2 mV)

Let’s see if we can pull even more from the OCZ ZX Series 850 W.

Overload Tests

Below you can see the maximum we could pull from this power supply. If we tried to pull more the unit would shut down, showing that its protections are working fine. During this extreme condition, however, noise and ripple levels at the +12 V outputs were above the maximum allowed, at 175 mV, and voltages on the +12 V outputs were below the minimum allowed, at +11.23 V (the minimum allowed is +11.40 V).

Input

Overload Test

+12VA

33 A (396 W)

+12VB

33 A (396 W)

+5V

20 A (100 W)

+3.3 V

20 A (66 W)

+5VSB

3 A (15 W)

-12 V

0.5 A (6 W)

Total

932 W

% Max Load

109.6%

Room Temp.

44.2° C

PSU Temp.

51.7° C

AC Power

1,098 W

Efficiency

84.9%

AC Voltage

107.8 V

Power Factor

0.999

Main Specifications

The specs of the OCZ ZX Series 850 W include:

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

Conclusions

The OCZ ZX Series 850 W is a fierce competitor to the Seasonic X-Series 850 W power supply. Both cost exactly the same (USD 200) and have similar performance and specifications (single +12 V rail, full modular cabling system, 90% efficiency at typical load). The OCZ model has as advantage coming with 12 SATA power connectors, while the Seasonic model comes with eight, while the Seasonic model has as advantages presenting a lower noise and ripple levels on its +12 V outputs (20 mV vs. 60 mV) and being able to safely deliver 1,000 W or more (during our overload tests with the OCZ model, it presented noise above the maximum allowed and voltages below the minimum allowed at its +12 V outputs, which didn’t happened with the Seasonic model).

So, picking one or the other will be a matter of personal taste.

However, there is one hidden secret about this power supply you should know. As explained, the Sparkle SCC-850AF power supply is internally identical to this OCZ unit, and it can be bought for only USD 140 (after rebate) at TigerDirect.com. There are only two major differences between the OCZ ZX Series 850 W and the Sparkle SCC-850AF: on the Sparkle model the main motherboard cable and the ATX12V/EPS12V cables are permanently attached to the power supply, and the fan and the connectors are purple. So, if you don’t mind these differences, you can save a lot of money.

Originally at http://www.hardwaresecrets.com/article/OCZ-ZX-Series-850-W-Power-Supply-Review/1204


© 2004-13, Hardware Secrets, LLC. All Rights Reserved.

Total or partial reproduction of the contents of this site, as well as that of the texts available for downloading, be this in the electronic media, in print, or any other form of distribution, is expressly forbidden. Those who do not comply with these copyright laws will be indicted and punished according to the International Copyrights Law.

We do not take responsibility for material damage of any kind caused by the use of information contained in Hardware Secrets.