OCZ ZS Series 650 W Power Supply Review

[nextpage title=”Introduction”]

The ZS Series is the latest mainstream power supply series from OCZ, with the 80 Plus Bronze certification. Available in 550 W, 650 W, and 750 W versions, these models don’t come with a modular cabling system. Let’s see if the 650 W version is a good buy.

The OCZ ZS Series power supplies are manufactured by Sirfa.

Figure 1: OCZ ZS Series 650 W power supply

Figure 2: OCZ ZS Series 650 W power supply

The OCZ ZS Series 650 W is 6.3” (160 mm) deep, using a 135 mm ball bearing fan on its bottom (Globe Fan RL4Z B1342512H).

This unit doesn’t have a modular cabling system, and all cables are protected with nylon sleeves. This power supply comes with the following cables:

• Main motherboard cable with a 20/24-pin connector, 19.3” (49 cm) long
• One cable with two ATX12V connectors that together form an EPS12V connector, 26.8” (68 cm) long
• One cable with one six-pin connector for video cards, 24.4” (62 cm) long
• One cable with one six/eight-pin connector for video cards, 24.4” (62 cm) long
• One cable with four SATA power connectors, 15.4” (39 cm) to the first connector, 3.2” (8 cm) between connectors
• One cable with four SATA power connectors, 28” (71 cm) to the first connector, 3.2” (8 cm) between connectors
• One cable with four standard peripheral power connectors, 24.4” (62 cm) to the first connector, 3.2” (8 cm) between connectors

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

The cable configuration is excellent for a mainstream product, with eight SATA power connectors and two video card power connectors. As you can see, this power supply doesn’t come with a floppy disk drive power connector, and the distance between SATA and peripheral power connectors is too short.

Figure 3: Cables

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

[nextpage title=”A Look Inside the OCZ ZS Series 650 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.

Figure 4: Top view

Figure 5: Front quarter view

Figure 6: Rear quarter view

Figure 7: The printed circuit board

[nextpage title=”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 one X capacitor and two Y capacitors more than the minimum required.

Figure 8: Transient filtering stage (part 1)

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 ZS Series 650 W.

[nextpage title=”Primary Analysis”]

On this page we will take an in-depth look at the primary stage of the OCZ ZS Series 650 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses two GBU805 rectifying bridges, attached to an individual heatsink. These components support up to 8 A at 100° C each, 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 particular components. The real limit will depend on all the components combined in this power supply.

Figure 10: Rectifying bridges

The active PFC circuit uses two IPW60R190C6 MOSFETs, each supporting up to 20.2 A at 25° C or 12.8 A at 100° C in continuous mode (note the difference temperature makes), or 59 A at 25° C in pulse mode. These transistors present a 190 mΩ resistance when turned on, a characteristic called RDS(on). The lower the number t
he better, meaning that the transistor will waste less power, and the power supply will have a higher efficiency.

Figure 11: Active PFC diode and transistors

The electrolytic capacitor that filters the output of the active PFC circuit is Japanese, from Matsushita (Panasonic), and labeled at 85° C.

In the switching section, two SPP20N60C3 MOSFETs are used in the traditional two-transistor forward configuration. Each transistor supports up to 20.7 A at 25° C or 13.1 A at 100° C in continuous mode, or 62.1 A at 25° C in pulse mode, with an RDS(on) of 190 mΩ.

Figure 12: Switching transistors

The primary is controlled by the popular CM6800 active PFC/PWM combo controller.

Figure 13: Active PFC/PWM combo controller

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

[nextpage title=”Secondary Analysis”]

The OCZ ZS Series 650 W has eight Schottky rectifiers attached to the 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 percent.

The +12 V output uses four S30D45C Schottky rectifiers (30 A, 15 A per internal diode at 125° C, 0.70 V maximum voltage drop), giving us a maximum theoretical current of 86 A or 1,029 W for this output.

The +5 V output uses two PFR30L45CT Schottky rectifiers (30 A, 15 A per internal diode at 120° C, 0.52 V maximum voltage drop), giving us a maximum theoretical current of 43 A or 214 W for this output.

The +3.3 V output uses another two PFR30L45CT Schottky rectifiers, giving us a maximum theoretical current of 43 A or 141 W for this output.

Figure 14: The +12 V, +5 V, and +3.3 V rectifiers

This power supply uses an ST9S423 monitoring integrated circuit. Unfortunately, this chip isn’t listed at the manufacturer’s website, so we couldn’t confirm which protections this power supply really supports.

Figure 15: Monitoring circuit

The electrolytic capacitors available in the secondary are also Japanese, from Chemi-Con, and are labeled at 105° C.

[nextpage title=”Power Distribution”]

In Figure 16, you can see the power supply label containing all the power specs.

Figure 16: Power supply label

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

How much power can this unit really deliver? Let’s find out.

[nextpage title=”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 inputs were connected to the power supply’s single +12 V rail.

Input	Test 1	Test 2	Test 3	Test 4	Test 5
+12VA	5 A (60 W)	10 A (120 W)	15 A (180 W)	20 A (240 W)	24 A (288 W)
+12VB	5 A (60 W)	10 A (120 W)	15 A (180 W)	20 A (240 W)	24 A (288 W)
+5 V	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	140.6 W	269.1 W	406.8 W	542.9 W	653.4 W
% Max Load	21.6%	41.4%	62.6%	83.5%	100.5%
Room Temp.	46.2° C	45.2° C	45.7° C	47.3° C	49.8° C
PSU Temp.	45.4° C	45.8° C	46.3° C	47.2° C	48.9° C
Voltage Regulation	Pass	Pass	Pass	Pass	Pass
Ripple and Noise	Pass	Pass	Pass	Pass	Pass
AC Power	166.1 W	311.8 W	475.4 W	647.0 W	796.0 W
Efficiency	84.6%	86.3%	85.6%	83.9%	82.1%
AC Voltage	113.5 V	112.3 V	110.0 V	107.9 V	105.3 V
Power Factor	0.958	0.9 77	0.988	0.993	0.995
Final Result	Pass	Pass	Pass	Pass	Pass

The OCZ ZS Series 650 W passed our tests with flying colors. It can really deliver its labeled wattage at high temperatures.

Efficiency was between 84% and 86% when we pulled between 20% and 80% of the unit’s labeled power (i.e., between 130 W and 520 W). At full load (650 W), efficiency was at 82%. This is great to see, because several power supplies with 80 Plus Bronze certification that we’ve tested aren’t capable of sustaining 82% efficiency at high temperatures.

Voltages were closer to their nominal values (3% regulation) during all tests, which is terrific to see on a mainstream unit. The ATX12V specification 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 low at all times. 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.

Figure 17: +12VA input from load tester during test five at 653.4 W (51.4 mV)

Figure 18: +12VB input from load tester during test five at 653.4 W (51.2 mV)

Figure 19: +5V rail during test five at 653.4 W (13.4 mV)

Figure 20: +3.3 V rail during test five at 653.4 W (11.4 mV)

Let’s see if we can pull more than 650 W from this unit.

[nextpage title=”Overload Tests”]

Below you can see the maximum we could pull from this power supply. We couldn’t pull more than that because the power supply shut down, showing that its protections were working just fine. During this test, voltages were still inside the tighter 3% regulation, and noise and ripple levels were still low.

Input	Overload Test
+12VA	28 A (336 W)
+12VB	28 A (336 W)
+5 V	12 A (60 W)
+3.3 V	12 A (39.6 W)
+5VSB	3 A (15 W)
-12 V	0.5 A (6 W)
Total	782.4 W
% Max Load	120.4%
Room Temp.	44.7° C
PSU Temp.	46.3° C
AC Power	977 W
Efficiency	80.1%
AC Voltage	107.3 V
Power Factor	0.996

[nextpage title=”Main Specifications”]

The main specifications for the OCZ ZS Series 650 W power supply include:

• Standards: ATX12V 2.2
• Nominal labeled power: 650 W
• Measured maximum power: 782.4 W at 44.7° C ambient
• Labeled efficiency: Up to 85%, 80 Plus Bronze certification
• Measured efficiency: Between 82.1% and 86.3%, at 115 V (nominal, see complete results for actual voltage)
• Active PFC: Yes
• Modular Cabling System: No
• Motherboard Power Connectors: One 24-pin connector and two ATX12V connectors that together form an EPS12V connector
• Video Card Power Connectors: One six-pin and one six/eight-pin connector on separate cables
• SATA Power Connectors: Eight on two cables
• Peripheral Power Connectors: Four on one cable
• Floppy Disk Drive Power Connectors: None
• Protections (as listed by the manufacturer): Over voltage (OVP), over current (OCP), and short-circuit (SCP) protections
• Are the above protections really available? Couldn’t check.
• Warranty: Three years
• More Information: https://www.ocztechnology.com
• Average Price in the US*: USD 90.00

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

[nextpage title=”Conclusions”]

The OCZ ZS Series 650 W proved to be an outstanding mainstream power supply. It can really deliver its labeled wattage at high temperatures, and we could pull up to 780 W. Voltages are closer to their nominal values than required (3% voltage regulation), noise and ripple levels are low, and it provides  terrific efficiency for the market to which it is targeted, between 84% and 86% when we pulled between 20% and 80% of the unit’s labeled power (i.e., between 130 W and 520 W), and 82% at full load (650 W). Remember that several power supplies with 80 Plus Bronze certification we’ve tested weren’t capable of sustaining 82% efficiency at high temperatures. Another highlight of this unit is the presence of eight SATA power connectors.

The negative points of this power supply are the short distance between SATA and peripheral power cables, the absence of a floppy disk drive power connector (who needs that, anyway?), and pricing. At USD 90, we can’t say it is cheap. However, if you live in the US, you can get a USD 20 mail-in rebate, helping to soften the blow.

In summary, it is an excellent unit, and we recommend it.