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[nextpage title=”Introduction”]

The X7 power supply series from Huntkey is comprised of three models: 800 W (80 Plus Bronze), 900 W (80 Plus Silver), and 1,200 W (80 Plus Gold). All of them have a modular cabling system and make use of an interleaved PFC circuit and phase-shift full-bridge switching design in the primary. Let’s dissect the 900 W model, which has five +12 V rails.

Huntkey X7 900 W power supplyFigure 1: Huntkey X7 900 W power supply

Huntkey X7 900 W power supplyFigure 2: Huntkey X7 900 W power supply

The Huntkey X7 900 W is 6.3” (160 mm) deep, using a 140 mm ball bearing fan on its bottom (Yate Loon D14BH-12).

As mentioned, this unit has a modular cabling system with eight connectors, one for the ATX/EPS12V power cable, four for video cards, and three for peripheral and SATA power cables. Only the main motherboard cable is permanently attached to the power supply. This power supply comes with the following cables:

  • Main motherboard cable with a 20/24-pin connector, 19.3” (49 cm) long, permanently attached to the power supply
  • One cable with two ATX12V connectors that together form an EPS12V connector, 26.8” (68 cm) long, modular cabling system
  • Two cables, each with one six-pin connector for video cards, 22.8” (58 cm) long, modular cabling system
  • Two cables, each with one six-pin connector and one six/eight-pin connector for video cards, 22.8” (58 cm) to the first connector, 5.9” (15 cm) between connectors, modular cabling system
  • Two cables, each with three SATA power connectors and one standard peripheral power connector, 19.7” (50 cm) to the first connector, 5.9” (15 cm) between SATA connectors, 9.8” (25 cm) to the peripheral connector, modular cabling system
  • One cable with three standard peripheral power connectors and one floppy disk drive power connector, 19.7” (50 cm) to the first connector, 5.9” (15 cm) between connectors, modular cabling system

All wires are 18 AWG, which is the minimum recommended gauge, except the +12 V (yellow) wires on the main motherboard connector, which are thicker (16 AWG).

The cable configuration is good for a 900 W power supply, with six video card power connectors, allowing the installation of three high-end video cards that require two power connectors each. We think, however, that the number of SATA power connectors, six, is too low for a 900 W unit.

Huntkey X7 900 W power supplyFigure 3: Cables

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

[nextpage title=”A Look Inside the Huntkey X7 900 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.

Huntkey X7 900 W power supplyFigure 4: Top view

Huntkey X7 900 W power supplyFigure 5: Front quarter view

Huntkey X7 900 W power supplyFigure 6: Rear quarter view

Huntkey X7 900 W power supplyFigure 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 stage, the Huntkey X7 900 W power supply is impeccable, with two Y capacitors and two X capacitors more than the minimum required. The unit also has a relay to shut down the power supply in case of any of the protection circuits kicking in.

Huntkey X7 900 W power supplyFigure 8: Transient filtering stage (part 1)

Huntkey X7 900 W power supplyFigure 9: Transient filtering stage (part 2)

Huntkey X7 900 W power supplyFigure 10: Transient filtering stage (part 3)

On the next page, we will have a more detailed discussion about the components used in the Huntkey X7 900 W.

[nextpage title=”Primary Analysis”]

On this page we will take an in-depth look at the primary stage of the Huntkey X7 900 W. For a better understanding, please read our “Anatomy of Switching Power Supplies” tutorial.

This power supply uses one LL25XB60 rectifying bridge, which is attached to the same heatsink as the primary transistors. This bridge supports up to 25 A at 113° C, so in theory, you would be able to pull up to 2,875 W from a 115 V power grid. Assuming 80% efficiency, the bridge would allow this unit to deliver up to 2,300 W without burning itself out
. Of course, we are only talking about this particular component. The real limit will depend on all the components combined in this power supply.

Huntkey X7 900 W power supplyFigure 11: Rectifying bridge

The active PFC circuit of the X7 models uses a design called interleaved, which works by having two active PFC circuits operating with a 180° phase-shift between them, i.e., when one is turned on, the other is turned off and vice-versa. The end-result is a lower ripple on the output voltage of the active PFC circuit. The heart of this circuit is the UCC28070 chip, which carries the two required PWM controllers and drives the two active PFC circuits, each one based on an FQA24N50 MOSFET, which is capable of delivering up to 24 A at 25° C or 15.2 A at 100° C in continuous mode (note the difference temperature makes), or up to 96 A in pulse mode at 25° C, each. This transistor presents a 200 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.

Huntkey X7 900 W power supplyFigure 12: Interleaved active PFC controller

The output of the active PFC circuits is filtered by one 470 µF x 450 V electrolytic capacitor and one 330 µF x 450 V electrolytic capacitor connected in parallel. This is the equivalent of one 800 µF x 450 V. Both capacitors are Japanese, from Chemi-Con, and labeled at 85° C.

In the switching section, the Huntkey X7 900 W also makes use of a very unique design: phase-shift full-bridge. This is the first time we’ve seen a PC power supply using such a design. It is implemented using a UCC38950 PWM controller that is connected to two IR2113S driver chips, each one activating two of the four required transistors. Another four FQA24N50 MOSFETs are used here, and the specifications for these components were already discussed above.

Huntkey X7 900 W power supplyFigure 13: One of the active PFC diodes, one of the active PFC transistors, and two of the switching transistors

Huntkey X7 900 W power supplyFigure 14: The other two switching transistors, the other active PFC transistor, and the other active PFC diode

Huntkey X7 900 W power supplyFigure 15: The PWM controller and one of the drivers

Huntkey X7 900 W power supplyFigure 16: The other driver

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

[nextpage title=”Secondary Analysis”]

The Huntkey X7 900 W uses a synchronous design in its secondary, meaning that the diodes were replaced with transistors in order to increase efficiency. While the +12 V output uses a fully synchronous design, the +5 V and +3.3 V outputs use a half-synchronous design, where only the diodes in charge of the direct rectification were replaced with MOSFETs. The “freewheeling” part of the rectification continues to use Schottky diodes.

The +12 V output is rectified using four IRFB3206PbF MOSFETs, each one capable of handling up to 210 A at 25° C or 150 A at 100° C in continuous mode, or up to 840 A at 25° C in pulse mode, with an RDS(on) of only 2.4 mΩ.

The +5 V output uses an IRF1404 MOSFET for its direct rectification, a component that is capable of handling up to 202 A at 25° C or 143 A at 100° C in continuous mode, or up to 808 A at 25° C in pulse mode, with an RDS(on) of only 4 mΩ. For the “freewheeling” part of the rectification, one STPS3045CT Schottky rectifier is used. This rectifier supports up to 30 A (15 A per internal diode at 155° C), with a maximum voltage drop of 0.84 V.

The +3.3 V output uses another IRF1404 MOSFET and STPS3045CT Schottky rectifier. The specifications for these components were already discussed above.

Huntkey X7 900 W power supplyFigure 17: The +5 V transistor, two of the +12 V transistors, and the +3.3 V rectifier

Huntkey X7 900 W power supplyFigure 18: The +3.3 V transistor, two of the +12 V transistors, and the +5 V rectifier

The secondary transistors are monitored by a WT751002 chip, which only supports over voltage (OVP) and under voltage (UVP) protections. However, over current protection (OCP) is present, as we could test it, and is implemented using two LM339 voltage comparators.

Huntkey X7 900 W power supplyFigure 19: Monitoring circuit

The electrolytic capacitors used in the secondary are from KSC, Teapo, and Fcon, and labeled at 105° C, as usual.

[nextpage title=”Power Distribution”]

Figure 20 shows the power supply label containing all the power specs.

Huntkey X7 900 W power supplyFigure 20: Power supply label

As you can see, the manufacturer lists this unit as having five +12 V rails. Analyzing the circuit, we could clearly see five “shunts” (current sensors) matching the number of rails advertised by the manufacturer. See Figure 21. We also tested the over current protection (OCP) of each rail, and they worked as expected, proving that this unit really has five +12 V rails. Click here for a more detailed explanation.

Huntkey X7 900 W power supplyFigure 21: Shunts

The available +12 V rails are distributed as follows:

  • +12V1: Main motherboard cable, SATA and peripheral power connectors
  • +12V2: The ATX12V/EPS12V cable
  • +12V3: The two red connectors of the modular cabling system
  • +12V4: One of the blue connectors of the modular cabling system
  • +12V5: The other blue connector of the modular cabling system 

Let’s now see if this power supply can really deliver 900 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 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, the +12VA input was connected to the power supply +12V1 and +12V3 rails, while the +12VB input was connected to the power supply +12V2 and +12V3 rails.

Each +12 V input of our load tester is limited to 33 A, and that is why during test five we had to increase current at the +5 V and +3.3 V inputs more than we usually do.

Input Test 1 Test 2 Test 3 Test 4 Test 5
+12VA 6.5 A (78 W) 13 A (153 W) 20 A (240 W) 26.5 A (318 W) 33 A (396 W)
+12VB 6.5 A (78 W) 13 A (153 W) 19.5 A (234 W) 26.5 A (318 W) 33 A (396 W)
+5 V 2 A (10 W) 4 A (20 W) 6 A (30 W) 8 A (40 W) 14 A (70 W)
+3.3 V 2 A (6.6 W) 4 A (13.2 W) 6 A (19.8 W) 8 A (26.4 W) 14 A (46.2 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 183.7 W 356.8 W 533.4 W 707.9 W 901.9 W
% Max Load 20.4% 39.6% 59.3% 78.7% 100.2%
Room Temp. 46.1° C 46.4° C 45.4° C 46.0° C 47.8° C
PSU Temp. 49.0° C 49.6° C 50.5° C 50.9° C 53.2° C
Voltage Regulation Pass Pass Pass Pass Pass
Ripple and Noise Pass Pass Pass Pass Pass
AC Power 210.3 W 401.2 W 609.2 W 828.0 W 1102.0 W
Efficiency 87.4% 88.9% 87.6% 85.5% 81.8%
AC Voltage 114.7 V 113.2 V 110.6 V 108.0 V 104.4 V
Power Factor 0.975 0.988 0.996 0.999 0.998
Final Result Pass Pass Pass Pass Pass

The Huntkey X7 900 W can really deliver its labeled wattage at high temperatures.

Efficiency was between 85.58% and 88.9% when we pulled between 20% and 80% of the power supply labeled wattage (i.e., between 180 W and 720 W). When we pulled 900 W from this power supply, however, efficiency dropped to 81.8%, below the 85% minimum promised by the 80 Plus Silver certification. In fact, it even dropped below 80 Plus Bronze level (82 percent). This may have happened for two reasons.

First, there is the temperature. If you follow our reviews, you know that temperature plays a major role in efficiency. The higher the temperature, the lower the efficiency. We test  power supplies above 45° C, while the 80 Plus certification process is conducted at 23° C. The second reason we saw efficiency below the expected value is because the AC voltage dropped below 115 V as we increased load.

Voltage regulation was very good, with all voltages closer to their nominal values than required (three percent regulation), except the -12 V output during test one (at -11.43 V) and the +12VB input during test five (+11.52 V). These outputs were still inside the allowed range. The ATX12V specification states that positive voltages must be within 5% of their nominal values, and negative voltages must be within 10% of their nominal values.

Let’s discuss the ripple and noise levels on the next page.

[nextpage title=”Ripple and Noise Tests”]

Voltages at the power supply outputs must be as “clean” as possible, with no noise or oscillation (also known as “ripple”). The maximum ripple and noise levels allowed are 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. We consider a power supply as being top-notch if it can produce half or less of the maximum allowed ripple and noise levels.

The Huntkey X7 900 W provided extremely low ripple and noise levels, as you can see in the table below.

Input Test 1 Test 2 Test 3 Test 4 Test 5
+12VA 13.2 mV 18.2 mV 29.6 mV 41.2 mV 53.8 mV
+12VB 14.2 mV 19.4 mV 30.2 mV 43.2 mV 49.4 mV
+5 V 5.6 mV 6.2 mV 7.2 mV 9.4 mV 11.0 mV
+3.3 V 7.4 mV 10.6 mV 13.2 mV 16.2 mV 21.2 mV
+5VSB 8.6 mV 10.4 mV 12.2 mV 16.6 mV 20.2 mV
-12 V 10.2 mV 15.4 mV 21.6 mV 28.4 mV 34.2 mV

Below you can see the waveforms of the outputs during te
st five.

Huntkey X7 900 W power supplyFigure 22: +12VA input from load tester during test five at 901.9 W (53.8 mV)

Huntkey X7 900 W power supplyFigure 23: +12VB input from load tester during test five at 901.9 W (49.4 mV)

Huntkey X7 900 W power supplyFigure 24: +5V rail during test five at 901.9 W (11 mV)

Huntkey X7 900 W power supplyFigure 25: +3.3 V rail during test five at 901.9 W (21.2 mV)

Let’s see if we can pull more than 900 W from this unit.

[nextpage title=”Overload Tests”]

Below you can see the maximum we could pull from this power supply. Keep in mind that each +12 V input of our load tester is limited to 33 A, and that is why we couldn’t pull even more power from this unit. If we tried to pull anything about what is described in the table below, the unit would shut down immediately. Also, we couldn’t pull more than 21 A from each +12 V rail because the over current protection would kick in, which is great to see. During this extreme configuration, noise and ripple levels were still extremely low, in the same range as test five (see previous page). The +12 V and +3.3 V outputs got outside the tighter three percent regulation but were still inside the appropriate range. (+12VA at +11.64 V, +12VB at +11.44 V, and +3.3 V at +3.17 V).

Input Overload Test
+12VA 33 A (396 W)
+12VB 33 A (396 W)
+5 V 24 A (120 W)
+3.3 V 24 A (79.2 W)
+5VSB 3 A (15 W)
-12 V 0.5 A (6 W)
Total 974.9 W
% Max Load 108.3%
Room Temp. 48.9° C
PSU Temp. 57.7° C
AC Power 1249 W
Efficiency 78.1%
AC Voltage 102.1 V
Power Factor 0.997

[nextpage title=”Main Specifications”]

The main specifications for the Huntkey X7 900 W power supply include:

  • Standards: ATX12V 2.3 and EPS12V 2.92
  • Nominal labeled power: 900 W
  • Measured maximum power: 974.9 W at 48.9° C
  • Labeled efficiency: 80 Plus Silver certification
  • Measured efficiency: Between 81.8% and 88.9%, at 115 V (nominal, see complete results for actual voltage)
  • Active PFC: Yes
  • Modular Cabling System: Yes
  • Motherboard Power Connectors: One 20/24-pin connector permanently attached to the power supply and two ATX12V connectors that together form an EPS12V connector on the modular cabling system
  • Video Card Power Connectors: Four six-pin connectors and two six/eight-pin connectors on four cables, modular cabling system
  • SATA Power Connectors: Six on two cables, modular cabling system
  • Peripheral Power Connectors: Five on three cables, modular cabling system
  • Floppy Disk Drive Power Connectors: One
  • Protections (as listed by the manufacturer): Over current (OCP), over voltage (OVP), under voltage (UVP), over power (OPP), and short circuit (SCP)
  • Are the above protections really available? Yes.
  • Warranty: NA
  • More Information: https://www.huntkeydiy.com
  • MSRP in the US: NA

[nextpage title=”Conclusions”]

Huntkey decided to use a very unique design on the X7 900 W power supply, with an interleaved active PFC circuit and phase-shift full-bridge switching circuit. This is the first time we’ve seen a PC power supply using such designs.

Noise and ripple levels were extremely low, and voltages were almost always closer to their nominal value. We were, however, a little disappointed with the efficiency results. Efficiency was between 87% and 89% when we pulled between 20% and 60% of the power supply labeled wattage (i.e., between 180 W and 540 W). When we pulled 80% of the labeled wattage (i.e., 720 W), efficiency dropped to 85.5%, still a good number for most users, but this is what the unit should provide while delivering 900 W. At full load, efficiency dropped to 81.8%, a number that is below the minimum required for the 80 Plus Bronze certification (keep in mind that this unit is officially an 80 Plus Silver one).

The main reason that made efficiency fall below 85% at full load on our test was the AC voltage. The voltage in our lab is 115 V, but as we increased the power we were pulling from the unit, the AC voltage decreased, as you can see in the results table. An AC voltage below the expected value makes efficiency drop. We didn’t use any voltage stabilizer to keep the AC voltage constant because we wanted to see how the tested power supply behaves in a real-world scenario.

Remember that our tests are far more rigorous that those conducted during the 80 Plus certification. We test power supplies between 45° C and 50° C, while the 80 Plus tests are conducted at 23° C, a temperature that makes efficiency higher than in real-world conditions. Also, we try to pull as much current/power as possible from the +12 V outputs, as this reflects the usage of a modern PC. With a load configuration different from the one we use, efficiency numbers may be different.

We were also a bit disappointed with the relatively reduced number of SATA power connectors (six). We think a 900 W unit deserves at least nine of them. On the other hand, the X7 900 W provides six connectors for video cards, supporting, out of the box, three-way SLI and CrossFireX configurations.