BFG LS-450 Power Supply Review
By Gabriel Torres on June 10, 2009


Introduction

Hardware Secrets Golden Award

LS and MX are sister power supply series from BFG, with models from MX series coming with a modular cabling system, a 120 mm fan and an auxiliary 80 mm fan on the rear, while models from LS series use a 135 mm fan and no modular cabling system or second fan. Initially both series used the same internal design, however this is not entirely true anymore. All models from MX series are manufactured by Fore Point (one of the factories from Fortrex), but LS-450 and the new version of LS-550 (marked as “LS-550 (New)” on their website, being the model currently available at Newegg.com) are manufactured by Enhance Electronics. The old LS-550 and LS-680 are manufactured by Fore Point with the same design as models from MX series. According to BFG they will move all models from MX and LS to Enhance in the future, and when this happens units will be either released with new wattages (e.g., LS-700 instead of LS-680) or will have the name “New” added to their name.

Enhance Electronics is the manufacturer behind power supplies from Akasa, Real Power Pro series from Cooler Master and TruePower Quattro series from Antec. Keep in mind that not all models from these two brands are manufactured by Enhance.

BFG LS-450 power supply
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Figure 1: BFG LS-450 power supply.

BFG LS-450 power supply
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Figure 2: BFG LS-450 power supply.

LS-450 is a small power supply (5 ½” or 14 cm deep), has a 120 mm fan on its bottom and has active PFC circuit.

All cables use a nylon protection and all come from inside the power supply housing, as you can see in Figure 2.

The main motherboard cable uses a 20/24-pin connector and this unit comes with two ATX12V connectors that together form one EPS12V connector.

The reviewed power supply comes with five peripheral cables: one with one six-pin auxiliary power connector, two with three SATA power connectors each, one with three standard peripheral power plugs and one with three standard peripheral power plugs and one floppy disk drive power connector.

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

This unit presents a satisfactory number of connectors for an entry-level or mainstream PC with only one video card installed.

All cables are very long so you won’t have any trouble installing this power supply inside full-tower cases: the distance between the power supply housing and the first connector on each cable is of 21 21/32” (55 cm) and the distance between each connector on cables that have more than one plug is of 5 1/8” (13 cm).

BFG LS-450 power supply
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Figure 3: Cables.

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

A Look Inside The LS-450

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.

BFG LS-450 power supply
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Figure 4: Overall look.

BFG LS-450 power supply
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Figure 5: Overall look.

BFG LS-450 power supply
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Figure 6: Overall look.

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.

On this power supply this stage is flawless, with two X capacitors, one X capacitor after the rectifying bridge and two Y capacitors more than needed.

BFG LS-450 power supply
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Figure 7: Transient filtering stage (part 1).

BFG LS-450 power supply
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Figure 8: Transient filtering stage (part 2).

In the next page we will have a more detailed discussion about the components used in the BFG LS-450.

Primary Analysis

On this page we will take an in-depth look at the primary stage of BFG LS-450. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one GBU806 rectifying bridge in its primary, which can deliver up to 8 A at 100° C. This component is clearly overspec’ed: at 115 V this unit would be able to pull up to 920 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 736 W without burning this component. Of course we are only talking about this component and the real limit will depend on all other components from the power supply.

BFG LS-450 power supply
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Figure 9: Rectifying bridge.

On the active PFC circuit one SPW32N50C3 power MOSFET transistor is used, capable of delivering up to 32 A at 25° C or 20 A at 100° C in continuous mode (note the difference temperature makes) or 96 A in pulse mode at 25° C. This is the first time we’ve seen a power supply using only one transistor on the active PFC circuit.

The active PFC capacitor is Japanese from Chemi-Con and labeled at 105° C. This is good for two reasons. Usually manufacturers use 85° C capacitors here, so it is good to see a manufacturer using a capacitor with a higher temperature rating. Secondly, Japanese capacitors don’t suffer from leakage problems.

In the switching section, two STP12NM50 power MOSFET transistors are used on the traditional two-transistor forward configuration. Each one is capable of delivering up to 12 A at 25° C or 7.5 A at 100° C in continuous mode (note the difference temperature makes) or 48 A in pulse mode at 25° C.

BFG LS-450 power supply
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Figure 10: One of the switching transistors, active PFC diode and active PFC transistor.

The primary is controlled by a CM6806A PFC/PWM combo controller.

BFG LS-450 power supply
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Figure 11: PFC/PWM combo controller.

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

Secondary Analysis

This power supply uses four Schottky rectifiers on its secondary.

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 two rectifiers, however they are not connected in parallel. One STPS30L60CW has its two internal diodes connected in parallel and is in charge of the direct rectification (30 A at 130° C, i.e., 15 A per internal diode), while one 40CPQ060 has its two diodes connected in parallel and is in charge of the “freewheeling” portion of the rectification (i.e., discharging the coil). This device has a maximum current limit of 40 A (20 A per diode at 120° C). For our math we have to consider the part with the lower current limit, 30 A in our case. Applying the above formula gives us a maximum theoretical current of 43 A or 514 W for the +12 V output.

The +5 V output is produced by one STPS40L45CW Schottky rectifier, capable of delivering up to 40 A (20 A per internal diode at 130° C). This means the +5 V output has a maximum theoretical current of 29 A or 143 W.

The +3.3 V output is produced by another STPS40L45CW Schottky rectifier, which is capable of delivering up to 40 A (20 A per diode at 130° C), giving us a maximum theoretical current of 29 A or 94 W for the +3.3 V output.

BFG LS-450 power supply
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Figure 12: +3.3 V, +5 V and the two +12 V rectifiers.

The outputs are monitored by a PS223 integrated circuit, which supports the following protections: over current (OCP), under voltage (UVP), over voltage (OVP) and over temperature (OTP, not implemented on this power supply). Any other protection that this unit may have is implemented outside this integrated circuit.

BFG LS-450 power supply
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Figure 13: Monitoring integrated circuit.

Most electrolytic capacitors from the secondary are also Japanese, from Chemi-Con, but some models are from Teapo (Taiwanese company).

Power Distribution

In Figure 14, you can see the power supply label containing all the power specs.

BFG LS-450 power supply
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Figure 14: Power supply label.

This power supply has a single-rail design, so there is no point in talking about rail distribution.

Now let’s see if this power supply can really deliver 450 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 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.

+12V1 and +12V2 are the two independent +12V inputs from our load tester and during our tests both were connected to the single +12 V provided by this power supply.

Input

Test 1

Test 2

Test 3

Test 4

Test 5

+12V1

3 A (36 W)

6.5 A (78 W)

9.5 A (114 W)

13 A (156 W)

16 A (192 W)

+12V2

3 A (36 W)

6.5 A (78 W)

9.5 A (114 W)

13 A (156 W)

16 A (192 W)

+5V

1 A (5 W)

2 A (10 W)

4 A (20 W)

5 A (25 W)

6 A (30 W)

+3.3 V

1 A (3.3 W)

2 A (6.6 W)

4 A (13.2 W)

5 A (16.5 W)

6 A (19.8 W)

+5VSB

1 A (5 W)

1 A (5 W)

1 A (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

89.5 W

180.4 W

269.2 W

361.3 W

440.5 W

% Max Load

19.9%

40.1%

59.8%

80.3%

97.9%

Room Temp.

47.9° C

47.9° C

47.8° C

48.4° C

48.2° C

PSU Temp.

49.2° C

48.7° C

48.9° C

50.3° C

51.0° C

Voltage Stability

Pass

Pass

Pass

Pass

Pass

Ripple and Noise

Pass

Pass

Pass

Pass

Pass

AC Power

101 W

201 W

304 W

418 W

522 W

Efficiency

88.6%

89.8%

88.6%

86.4%

84.4%

Final Result

Pass

Pass

Pass

Pass

Pass

BFG LS-450 proved to be an excellent power supply. It could deliver its labeled power at 48.2° C with a very high efficiency, peaking 89.8% when delivering 40% of its labeled power (180 W). At full load efficiency was still very high, at 84.4%, which is outstanding.

The only problem we saw was voltage level at -12 V. This output has a higher 10% tolerance, so it can be anywhere between -13.2 V and -10.8 V. During test number one this output was at -10.81 V, touching this limit. During test two it was at -10.92 V, during test three it was at -11.00 V, during test four it was at -11.08 V and during test five it was at -11.16 V. All values were still inside the limits, but we’d prefer to see this output closer to the nominal -12 V.

Ripple and noise was another highlight from this product. Below you see the waveforms during test number five. Just to remember, the maximum allowed is 120 mV at +12 V and 50 mV at +5 V and +3.3 V. All values are peak-to-peak.

BFG LS-450 power supply
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Figure 15: +12V1 rail with power supply delivering 440.5 W (67.6 mV).

BFG LS-450 power supply
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Figure 16: +12V2 rail with power supply delivering 440.5 W (61.4 mV).

BFG LS-450 power supply
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Figure 17: +5V rail with power supply delivering 440.5 W (24.4 mV).

BFG LS-450 power supply
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Figure 18: +3.3 V rail with power supply delivering 440.5 W (21.8 mV).

Now let’s see if we could pull more than 450 W from this unit.

Overload Tests

Before overloading power supplies we always test first if the over current protection (OCP) circuit is active and at what level it is configured.

In order to do that we increased current on the +12 V rail until the power supply shut down. This happened when we tried to pull more than 43 A from it.

Manufacturers always leave a margin between what is written on the label (29 A in this case) and the level the OCP circuit is really configured (43 A in this case). We always like to see this margin as tight as possible and in this case we think OCP was configured at a value that is too high.

Then starting from test five we increased currents to the maximum we could with the power supply still running inside ATX specs. The results are below. When we tried to increase one more amp at any output ripple would go to the roof, meaning that the unit stopped working correctly.

Input

Maximum

+12V1

22 A (264 W)

+12V2

21 A (252 W)

+5V

6 A (30 W)

+3.3 V

1 A (3.3 W)

+5VSB

1 A (5 W)

-12 V

0.5 A (6 W)

Total

539.4 W

% Max Load

119.9%

Room Temp.

47.1° C

PSU Temp.

52.9° C

AC Power

669 W

Efficiency

80.6%

Even when overloaded this power supply presented efficiency above 80%.

Main Specifications

BFG LS-450 power supply specs include:

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

Conclusions

We were very impressed with BFG’s LS-450. While the manufacturer cautiously announces efficiency as “80% minimum,” in fact LS-450 is a high-efficiency product, with efficiency ranging from 84.4% and 89.8% at 115 V. And, of course, it can deliver its labeled power and some more at 47° C.

LS-450 is a good competitor to the new Thermaltake Litepower 450 W, which is also a high-efficiency 450 W power supply. Thermaltake’s model has as advantage an even higher efficiency, while the advantage of BFG LS-450 is having longer cables, more SATA power connectors and a better price: USD 70 at Newegg.com, or only USD 45 after a mail-in rebate (on BFG’s website it is sold by USD 90, so avoid buying it there!). This put this power supply as one of the best cost/benefit ratios for the savvy user that is building an entry-level or mainstream PC and wants to save both on the cost of the power supply and on the electricity bill.

Originally at http://www.hardwaresecrets.com/article/BFG-LS-450-Power-Supply-Review/732


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