Zalman ZM600-RS Power Supply Review

[nextpage title=”Introduction”]

Zalman has recently released a power supply series based on a resonant switching (RS) design, aptly named RS series. Let’s see if the 600 W model from this series is a good buy.

Like other power supplies from Zalman, ZM600-RS is manufactured by FSP.

We’ve already reviewed the 500 W model from this series and the printed circuit board from this other unit is different, so the 600 W model isn’t the same power supply as the 500 W with upgraded components.

Figure 1: Zalman ZM600-RS power supply.

Figure 2: Zalman ZM600-RS power supply.

Zalman ZM600-RS is only 5 ½” (140 mm) deep, using a 120 mm fan on its bottom and active PFC circuit, of course.

All cables are protected by nylon sleevings, which come from inside the power supply housing. All cables measure 21 5/8” (55 cm) between the housing and the first connector on the cable, except the SATA and peripheral cables, which have 19 ¾” (50 cm) between the power supply and the first connector on the cable and 5 7/8” (15 cm) between connectors. All wires are 18 AWG, which is the correct gauge to be used.

The cables included are:

• Main motherboard cable with a 20/24-pin connector.
• One cable with two ATX12V connectors that together form one EPS12V connector.
• Two auxiliary power cables for video cards with one six/eight-pin connector and one six-pin connector each.
• Two SATA power cables with three SATA power connectors each.
• One peripheral power cable with three standard peripheral power plugs.
• One peripheral power cable with three standard peripheral power plugs and one floppy disk drive power connector.

ZM600-RS comes with a better cable configuration than ZM500-RS, with each SATA and peripheral power cables having three connectors instead of only two. This power supply also comes with two cables for video cards with two connectors each, whereas the 500 W model comes with only one cable with two connectors installed. This way with this power supply you can install two high-end video cards that require two power connectors each at the same time. Of course we’d prefer if the unit used four separated cables instead of hanging two connectors on each cable.

Figure 3: Cables.

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

[nextpage title=”A Look Inside The Zalman ZM600-RS”]

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. As mentioned, this unit uses a different printed circuit board than the 500 W model.

Figure 4: Overall look.

Figure 5: Overall look.

Figure 6: Overall look.

[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.

This power supply is flawless on this stage, with two Y capacitors and two X capacitors more than the minimum required, plus an X capacitor after the rectifying bridge. Note how the filtering stage from this unit is located on a separated printed circuit board.

Figure 7: Transient filtering stage (part 1).

Figure 8: Transient filtering stage (part 2).

In the next page we will have a more detailed discussion about the components used in the Zalman ZM600-RS.

[nextpage title=”Primary Analysis”]

On this page we will take an in-depth look at the primary stage of Zalman ZM600-RS. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one D25XB60 rectifying bridge in its primary, which can deliver up to 25 A at 98° C if a heatsink is used, which is the case (without a heatsink the limit drops to 3.5 A at 25° C). At 115 V this unit would be able to pull up to 2,875 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 2,300 W without burning this component. That is what we call overspecification! Of course we are only talking about this component and the real limit will depend on all other components from the power supply.

Figure 9: Rectifying bridge.

On the active PFC circuit
two SPA20N60C3 power MOSFET transistors are used, each one capable of delivering up to 20.7 A at 25° C or 13.1 A at 100° C in continuous mode (note the difference temperature makes), or up to 62.1 A in pulse mode at 25° C. These transistors present a resistance of 190 mΩ when turned on, a characteristic called RDS(on). This number indicates the amount of power that is wasted, so the lower this number the better, as less power will be wasted thus increasing efficiency. These transistors are more powerful than the ones used on the 500 W model from Zalman RS series.

Figure 10: Active PFC diode and transistors.

This power supply uses a Taiwanese capacitor from Teapo labeled at 85° C to filter the output from the active PFC circuit.

In the switching section, two STP14NK50ZFP power MOSFET transistors are used, each one capable of delivering up to 14 A at 25° C or 7.6 A at 100° C in continuous mode, or up to 48 A at 25° C in pulse mode, with an RDS(on) of 380 mΩ. These are the exact same transistors used on the 500 W model.

Figure 11: Switching transistors.

The switching transistors are connected using a design called “LLC resonant,” also known as a series parallel resonant converter, being controlled by an L6598 integrated circuit. So far we’ve seen only a few power supplies using this kind of design, like Seasonic X-Series 650 W, Thermaltake Toughpower 800 W, SilverStone Nightjar 400 W and Zalman ZM500-RS.

Figure 12: Resonant controller.

The active PFC circuit is controlled by a separated integrated circuit, an ICE1PCS02.

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

[nextpage title=”Secondary Analysis”]

This power supply has nine Schottky rectifiers attached to the secondary heatsink. Eight of them are from the model: SBL3040CT (30 A, 15 A per internal diode at 100° C, 0.55 V voltage drop). The ninth rectifier, an SBL1045CT (10 A, 5 A per internal diode at 95° C, 0.55 V voltage drop) is in charge of the +5VSB output. This configuration is identical to the one used on the 500 W model.

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%.

The +12 V output is produced by four of the rectifiers, giving us a maximum theoretical current of 86 A or 1,029 W.

The +5 V output is produced by two of the rectifiers, giving us a maximum theoretical current of 43 A or 214 W.

The +3.3 V output is produced by the last two rectifiers, giving us a maximum theoretical current of 43 A or 141 W.

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.

Figure 13: +12 V, +5 V, +3.3 V and +5VSB rectifiers.

The outputs are monitored by a PS232 integrated circuit, which supports the following protections: over current (OCP), under voltage (UVP) and over voltage (OVP). Any other protection that this unit may have is implemented outside this integrated circuit.

Figure 14: Monitoring integrated circuit.

Electrolytic capacitors from the secondary are also from Teapo and labeled at 105° C.

[nextpage title=”Power Distribution”]

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

Figure 15: Power supply label.

This power supply has four virtual rails (the 500 W model has only two), distributed like this:

• +12V1 (yellow with black stripe wire): ATX12V/EPS12V connectors.
• +12V2 (solid yellow wire): One of the video card power cables.
• +12V3 (yellow with blue stripe wire): Main motherboard cable, SATA and peripheral cables.
• +12V4 (yellow with white stripe wire): The other video card power cable.

This configuration is listed on the power supply label, which certainly helps advanced users (not shown in Figure 15).

This distribution is perfect since it separated the CPU (ATX12V/EPS12V connectors) from the video card(s).

Now let’s see if this power supply can really deliver 600 W.

[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 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.

The +12V1 and +12V2 inputs listed below are the two +12 V independent inputs from our load tester. During this test the +12V1 input was connected to the power supply +12V2 and +12V3 rails while the +12V2 input was connected to the power supply +12V1 rail.

Input	Test 1	Test 2	Test 3	Test 4	Test 5
+12V1	4 A (48 W)	9 A (108 W)	13 A (156 W)	17.5 A (210 W)	21.5 A (258 W)
+12V2	4 A (48 W)	9 A (108 W)	13 A (156 W)	17.5 A (210 W)	21.5 A (258 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)	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	116.9 W	246.9 W	362.4 W	489.2 W	603.4 W
% Max Load	19.5%	41.2%	60.4%	81.5%	100.6%
Room Temp.	45.2° C	44.4° C	44.6° C	46.0° C	50.2° C
PSU Temp.	50.1° C	50.5° C	51.2° C	53.5° C	58.4° C
Voltage Regulation	Pass	Pass	Pass	Pass	Pass
Ripple and Noise	Pass	Pass	Fail on -12 V	Fail on -12 V	Fail on -12 V
AC Power	139.3 W	286.2 W	423.8 W	584.8 W	753.0 W
Efficiency	83.9%	86.3%	85.5%	83.7%	80.1%
AC Voltage	118.2 V	116.9	115.3 V	114.2 V	112.8 V
Power Factor	0.992	0.997	0.998	0.998	0.998
Final Result	Pass	Pass	Pass	Pass	Pass

Zalman ZM600-RS can really deliver its labeled wattage at high temperatures.

Efficiency was high when we pulled between 20% and 80% from its labeled wattage (i.e., between 120 W and 480 W), being between 83.7% and 86.3%. At full load (600 W) efficiency dropped to 80.1%, still above the 80% mark.

This unit is 80 Plus Bronze certified, meaning that it should present 82% efficiency at full load. This didn’t happen because differently from Ecos Consulting we test power supplies at high temperatures, and efficiency drops with temperature (read our Can We Trust the 80 Plus Certification? article for more details).

Voltages were always inside the allowed range.

This unit presented a noise level above the maximum allowed on its -12 V output during tests four and five. Usually we don’t “fail” the whole power supply when it presents noise out of range on its -12 V output. But you should note that noise at +12 V outputs was very high during test five, with the power supply almost touching the maximum allowed (120 mV). The maximum allowed for the +5 V and +3.3 V outputs is 50 mV. We saw this same high electrical noise problem with the 500 W version from this unit.

Figure 16: +12V1 input from load tester at 603.4 W (102.6 mV).

Figure 17: +12V2 input from load tester at 603.4 W (102.4 mV).

Figure 18: +5V rail with power supply delivering 603.4 W (34.2 mV).

Figure 19: +3.3 V rail with power supply delivering 603.4 W (25.4 mV).

When we tried to overload this power supply noise level at +12 V outputs was outside the maximum allowed value, and we only consider an overloading well succeeded if all parameters are within specs, which was not the case.

[nextpage title=”Main Specifications”]

Zalman ZM600-RS power supply specs include:

• ATX12V 2.3
• Nominal labeled power: 600 W.
• Measured maximum power: 603.4 W at 50.2° C (above that noise level was outside specs).
• Labeled efficiency: 87% maximum at 230 V (80 Plus Bronze certified)
• Measured efficiency: Between 80.1% and 86.3% at 115 V (nominal, see complete results for actual voltage).
• Active PFC: Yes.
• Modular Cabling System: No.
• Motherboard Power Connectors: One 20/24-pin connector and two ATX12V connectors that together form an EPS12V connector.
• Video Card Power Connectors: Two six-pin and two six/eight-pin connectors on two cables.
• SATA Power Connectors: Six in two cables.
• Peripheral Power Connectors: Six in two cables.
• Floppy Disk Drive Power Connectors: One.
• Protections: Over voltage (OVP, not tested), under voltage (UVP, not tested), over current (OCP, not tested), over temperature (OTP, not tested) and short-circuit protection (SCP, tested and working).
• Warranty: Three years
• Real Manufacturer: FSP
• More Information: https://www.zalman.com
• Average price in the US*: USD 125.00.

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

[nextpage title=”Conclusions”]

Zalman ZM600-RS presents high efficiency between 83.7% and 86.3% if you pull up to 80% (480 W) from it. At full load, however, efficiency drops to 80.1%. This power supply is 80 Plus Bronze certified, meaning that it should present 82% efficiency at full load, but as we have exposed on our Can We Trust the 80 Plus Certification? article, Ecos Consulting, the company behind the 80 Plus certification, uses an unrealistic room temperature to test power supplies, and efficiency drops with temperature.

Ripple and noise level at +12 V rails was too high while the power supply was delivering 600 W, at 102 mV, too close to the 120 mV limit, and the -12 V output presented noise level above the 120 mV limit when the unit was delivering 480 W and above (140 mV).

Its cable configuration is definitel
y better than the one from ZM500-RS, presenting one additional video card power cable with two connectors and one extra SATA and peripheral power connector on each SATA and peripheral cable.

The problem with Zalman products these days is pricing. This unit is sold in the US for USD 125, which is a little bit above the level we could give a definite buy recommendation. At this price level we have Nexus RX-6300, which provides higher efficiency, higher wattage, lower ripple and noise level and a modular cabling system. On the other hand it presents higher efficiency than products that are sold for a lower price, like the units from Seventeam (ST-650P-AF and ST-750P-AF) and SilverStone Element ST75EF.

The new Zalman ZM600-RS is a good product if you have USD 125 on your budget to spend on a power supply and can’t find Nexus RX-6300.