Antec VP350 Power Supply Review
By Gabriel Torres on March 1, 2012


Introduction

The Basiq power supply series from Antec is targeted to users with serious budget restrictions. The new VP350 and VP450 models are the most entry-level power supplies offered by Antec, as they don’t have a PFC circuit or 80 Plus certification. We’ve already reviewed the VP450, which achieved terrific performance for its class. Now it is time for us to test the 350 W model.

While the VP450 model is manufactured by FSP, the VP350 is manufactured by Delta. Therefore, they are based on different designs.

Antec VP350 power supply
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Figure 1: Antec VP350 power supply

Antec VP350 power supply
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Figure 2: Antec VP350 power supply

The Antec VP350 is 5.5” (140 mm) deep, using a 120 mm sleeve bearing fan on its bottom.

This unit doesn’t have a modular cabling system, and only the main motherboard cable uses a nylon sleeve, which comes from inside the unit. This power supply comes with the following cables:

All wires are 18 AWG wires, which is the minimum recommended gauge.

The cable configuration is excellent for a budget 350 W power supply.

Antec VP350 power supply
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Figure 3: Cables

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

A Look Inside the Antec VP350

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. As already explained, this power supply doesn’t share the same platform with the 450 W model.

Antec VP350 power supply
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Figure 4: Top view

Antec VP350 power supply
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Figure 5: Front quarter view

Antec VP350 power supply
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Figure 6: Rear quarter view

Antec VP350 power supply
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Figure 7: The 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. 

The Antec VP350 has four Y capacitors and one X capacitor more than the minimum required. There are two MOVs in parallel to the electrolytic capacitors from the voltage doubler circuit.

Antec VP350 power supply
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Figure 8: Transient filtering stage (part 1)

Antec VP350 power supply
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Figure 9: Transient filtering stage (part 2)

On the next page, we will have a more detailed discussion about the components used in the Antec VP350.

Primary Analysis

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

This power supply uses one T8KB80 rectifying bridge, which is not attached to a heatsink. We couldn’t find the datasheet for this component, but it is clear that it is an 8 A part, so in theory, you would be able to pull up to 920 W from a 115 V power grid. Assuming 80% efficiency, the bridge would allow this unit to deliver up to 736 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.

Antec VP350 power supply
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Figure 10: Rectifying bridge

As mentioned before, this power supply doesn’t have a PFC circuit.

The voltage doubler circuit uses two 470 µF x 220 V electrolytic capacitors from CapXon and labeled at 105° C.

Usually, power supplies without a PFC circuit are based on the obsolete half-bridge design; the Antec VP350 uses the single-transistor forward configuration, which is better. The Antec VP450, on the other hand, uses the two-transistor forward configuration, which is excellent.

In the switching section, one STW12NK90Z MOSFET is used in the single-transistor forward configuration, supporting up to 11 A at 25° C or 7 A at 100° C in continuous mode, or up to 44 A at 25° C in pulse mode, with an RDS(on) of 880 mΩ, which is very high (i.e., low efficiency).

Antec VP350 power supply
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Figure 11: The switching transistor

The switching transistor is controlled by an NCP1252 PWM controller.

Antec VP350 power supply
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Figure 12: PWM controller

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

Secondary Analysis

The Antec VP350 uses a regular design in its secondary, with Schottky rectifiers.

The maximum theoretical current that 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 two SBR20A100CT Schottky rectifiers (20 A, 10 A per internal diode at 150° C, 0.85 V maximum voltage drop). This gives us a maximum theoretical current of 29 A or 343 W for the +12 V output.

The +5 V output uses two MBR2045CTG Schottky rectifiers (20 A, 10 A per internal diode at 165° C, 0.84 V maximum voltage drop). This gives us a maximum theoretical current of 29 A or 143 W for the +5 V output.

The +3.3 V output uses one STPS3045CT Schottky rectifier (30 A, 15 A per internal diode at 155° C, 0.84 V maximum voltage drop). This gives us a maximum theoretical current of 21 A or 71 W for the +3.3 V output.

Antec VP350 power supply
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Figure 13: The -12 V voltage regulator and the +3.3 V, +5 V, and +12 V rectifiers

This power supply uses a DWA106N161 monitoring integrated circuit. Unfortunately, we couldn’t find its datasheet, so we can’t comment on the protections this power supply really has. Additionally, this unit has an AS393 voltage comparator, which is equivalent to the famous LM393.

Antec VP350 power supply
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Figure 14: Monitoring circuit

The electrolytic capacitors that filter the outputs are from Taicon and labeled at 105° C, as usual.

Power Distribution

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

Antec VP350 power supply
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Figure 15: Power supply label

As you can see, this power supply is sold as having two +12 V rails, which seems to be correct, since we could clearly see two “shunts” (current sensors). See Figure 16. Click here to understand more about this subject.

Antec VP350 power supply
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Figure 16: Shunts

The two +12 V rails are distributed as follows:

This is the typical distribution used by power supplies with two +12 V virtual rails.

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

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 rail, while the +12VB input was connected to the power supply +12V2 rail.

Input

Test 1

Test 2

Test 3

Test 4

Test 5

+12VA

2 A (24 W)

5 A (60 W)

7 A (84 W)

9 A (108 W)

11.25 A (135 W)

+12VB

2 A (24 W)

5 A (60 W)

6.5 A (78 W)

9 A (108 W)

11 A (132 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)

1.5 A (7.5 W)

2 A (10 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

66.3 W

136.3 W

206.3 W

276.3 W

346.8 W

% Max Load

18.9%

38.9%

58.9%

78.9%

99.1%

Room Temp.

47.6° C

46.6° C

46.1° C

46.7° C

49.5° C

PSU Temp.

48.3° C

48.2° C

48.2° C

48.7° C

50.9° C

Voltage Regulation

Pass

Pass

Pass

Pass

Pass

Ripple and Noise

Pass

Pass

Pass

Pass

Pass

AC Power

85.0 W

168.3 W

257.9 W

353.4 W

455.0 W

Efficiency

78.0%

81.0%

80.0%

78.2%

76.2%

AC Voltage

119.1 V

118.4 V

117.7 V

116.7 V

114.7 V

Power Factor

0.562

0.620

0.638

0.648

0.658

Final Result

Pass

Pass

Pass

Pass

Pass

The Antec VP350 can really deliver its labeled wattage. Its performance, however, is way inferior to its 450 W sister’s.

Efficiency was between 76.2% and 81% during our tests.

Voltage regulation was outstanding, with all voltages closer to their nominal values than required (three percent regulation), except for the -12 V output, which was 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.

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 Antec VP350 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

17.2 mV

17.6 mV

26.2 mV

32.2 mV

39.2 mV

+12VB

17.0 mV

17.2 mV

26.6 mV

34.2 mV

39.6 mV

+5 V

6.0 mV

7.2 mV

9.4 mV

11.4 mV

13.4 mV

+3.3 V

10.2 mV

8.4 mV

10.8 mV

10.6 mV

11.0 mV

+5VSB

8.6 mV

8.6 mV

9.0 mV

12.4 mV

11.0 mV

-12 V

27.8 mV

44.4 mV

40.0 mV

48.6 mV

61.2 mV

Below you can see the waveforms of the outputs during test five.

Antec VP350 power supply
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Figure 17: +12VA input from load tester during test five at 346.8 W (39.2 mV)

Antec VP350 power supply
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Figure 18: +12VB input from load tester during test five at 346.8 W (39.6 mV)

Antec VP350 power supply
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Figure 19: +5V rail during test five at 346.8 W (13.4 mV)

Antec VP350 power supply
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Figure 20: +3.3 V rail during test five at 346.8 W (11 mV)

Let’s see if we can pull more than 350 W from this unit.

Overload Tests

Below you can see the maximum we could pull from this power supply. The objective of this test is to see if the power supply has its protection circuits working properly. This unit failed this test, as its switching transistor exploded right after we finished collecting data, meaning that the unit doesn’t have over power protection (OPP) or it is not configured correctly. During this test, noise and ripple levels were still extremely low and voltages were still inside the tighter 3% range.

Input

Overload Test

+12VA

16 A (192 W)

+12VB

16 A (192 W)

+5 V

10 A (50 W)

+3.3 V

10 A (33 W)

+5VSB

2 A (10 W)

-12 V

0.5 A (6 W)

Total

475.3 W

% Max Load

135.8%

Room Temp.

46.9° C

PSU Temp.

50.4° C

AC Power

688.0 W

Efficiency

69.1%

AC Voltage

110.8 V

Power Factor

0.666

Main Specifications

The main specifications for the Antec VP350 power supply include:

* Researched at Google Shopping on the day we published this review.

Conclusions

The Antec VP350 is an “honest” budget power supply that can really deliver its labeled wattage, with superb voltage regulation and outstandingly low noise and ripple levels. The only issue with this power supply is its low efficiency below 80%. However, it presents 80% efficiency if you pull between 40% and 60% of its labeled wattage, i.e., between 140 W and 210 W. This is good enough for users looking for a budget 350 W power supply.

However, we were disappointed, since its sister, the VP450, achieved outstanding efficiency numbers, always above 80%. This occurred because they use completely different designs: the VP350 uses a single-transistor forward configuration with a high RDS(on) transistor, while the VP450 uses a two-transistor forward configuration with transistors with a lower RDS(on).

Since the price difference between the VP350 and the VP450 is so small – only USD 5 – we recommend that you buy the VP450 instead.

Originally at http://www.hardwaresecrets.com/article/Antec-VP350-Power-Supply-Review/1500


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