GlacialPower GP-PS550BP Power Supply

[nextpage title=”Introduction”]

GP-PS550BP is a very simple 550 W power supply manufactured by GlacialPower with all sales handled by GlacialTech, featuring passive PFC and no extra fancy features, coming with a MSRP of only USD 65. We completely disassembled this unit to take a look. Is this a good buy? Let’s see.

Figure 1: GlacialPower GP-PS550BP.

Figure 2: GlacialPower GP-PS550BP.

As you can see on Figures 1 and 2 this power supply doesn’t bring any extra fancy features like a modular cabling system or a 120 mm fan, but it has two PCI Express power connectors for SLI or CrossFire, and also passive PFC, as we will show in the next page (power supplies with passive PFC still have a 110/220 V switch, as you can see in Figure 1).

According to GlacialPower, this unit has 78% efficiency at 230 V, which is a little bit lower than the 80%-85% efficiency that power supplies with active PFC have. On the other hand GlacialPower says that their 550 W power rating is labeled at 45° C, which is outstanding. Several power supplies on the market are labeled at 25° C, meaning that when the power supply is running on a real-world environment its maximum power is lower than the labeled maximum power, because the power supply capacity of delivering power is reduced as its internal temperature increases.

Efficiency means less power loss – an 80% efficiency means that 80% of the power pulled from the power grid will be converted in power on the power supply outputs and only 20% will be wasted. This translates into less consumption from the power grid (as less power needs to be pulled in order to generate the same amount of power on its outputs), meaning lower electricity bills – compare to 50% to 60% on regular power supplies.

PFC (Power Factor Correction), on the other hand, provides a better usage of the power grid and allows this power supply to be comply with the European law, making GlacialTech able to sell it in that continent (you can read more about PFC on our Power Supply Tutorial). There are three choices for PFC: none, active or passive. “Active” and “passive” refers to the kind of components used to make the PFC circuit: semiconductors (transistors and diodes) or just a transformer, respectively.

This power supply comes with five peripheral power cables: two PCI Express auxiliary power cables, one peripheral power cable containing two standard peripheral power connectors and one floppy disk drive power connector, one peripheral power cable containing three standard peripheral power connectors and one Serial ATA power cable containing two SATA power connectors. We think this power supply should have at least two more SATA power connectors.

The auxiliary PCI Express power connectors use separated wires coming from inside the power supply. On cheap power supplies these two connectors are connected in parallel to the same set of wires that come from inside the power supply.

Only the main power cable uses a plastic sleeving. This cable uses a 24-pin power connector that can be transformed into a 20-pin one if necessary.

The majority of wires used on this power supply are 18 AWG, which is good enough for this power supply class. The wires used on the PCI Express power connectors are 20 AWG, and we think that GlacialPower should have used 18 AWG here as well.

This power supply is really manufactured by GlacialPower, as we could find its name on all printed circuit boards inside the unit.

[nextpage title=”A Look Inside The GlacialPower GP-PS550BP”]

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.

In this page, we will have an overall look, while in the next page we will discuss in details the quality and rating of the components used.

On Figures 3 and 4 you can have an overall look from inside GlacialPower GP-PS550BP. The transformer on the upper right corner in Figure 3 and on the left side in Figure 4 is the passive PFC transformer. As you can imagine, passive PFC solutions add more weight to the power supply.

Figure 3: Inside GlacialPower GP-PS550BP.

Figure 4: Inside GlacialPower GP-PS550BP.

In the next page we will have a more detailed discussion about the components used in the GlacialPower GP-PS550BP.

[nextpage title=”Transient Filtering Stage”]

As we mentioned on other articles, 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 than that, usually removing the MOV, which is essential for cutting spikes coming from the power grid, and the first coil.

Even though this power supply from GlacialPower has one more component than the necessary – one extra X capacitor –, it doesn’t have a MOV, which is a sin.

Figure 5: Transient filtering stage (part 1).

Figure 6: Transient filtering stage (part 2).

[nextpage title=”Primary Analysis”]

We were very curious to check what components were chosen for the power section of this power supply and also how they were set together, i.e., the design used. We were willing to see if the components could really deliver the power announced by GlacialPower.

From all the specs provided on the databook of each component, we are more interested on the maximum continuous current parameter, given in ampères or amps for short. To find the maximum theoretical power capacity of the component in watts we need just to use the formula P = V x I, where P is power in watts, V is the voltage in volts and I is the current in ampères.

We also need to know under which temperature the component manufacturer measured the component maximum current (this piece of information is also found on the component databook). The higher the temperature, the lower
current semiconductors can deliver. Currents given at temperatures lower than 50° C are no good, as temperatures below that don’t reflect the power supply real working conditions.

Keep in mind that this doesn’t mean that the power supply will deliver the maximum current rated for each component as the maximum power the power supply can deliver depends on other components used – like the transformer, coils, the PCB layout, the wire gauge and even the width of the printed circuit board traces – not only on the specs of the main components we are going to analyze.

For a better understanding of what we are talking here, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one GBU1506 rectifying bridge in its primary stage, which can deliver up to 15 A each (rated at 55° C with heatsink; the bridge used on this power supply wasn’t using a heatsink). The manufacturer should have added a heatsink here. Without a heatsink the maximum current this bridge can support is only 3.2 A, which is a value that is too low, allowing the power supply to pull only up to 368 W from a 115 V power grid without burning this component. At a typical 80% efficiency this would translate into only 294.4 W on the power supply outputs. Unfortunately at the moment we analized this power supply we didn’t have a load tester yet so we cannot say whether or not this unit can deliver its labeled power.

The switching section uses a single-transistor forward configuration, using two STW12NK90Z power MOSFET transistors in parallel in order to double the current capacity of the switcher. Each transistor has a maximum current of 11 A (at 25° C) or 7 A (at 100° C) in continuous mode or 44 A (at 25° C) in pulsating mode, which is the mode used, as the PWM circuit feeds these transistors with a square waveform. So the total capacity for the switcher used on this power supply is of 88 A at 25° C.

This power supply uses a separated switcher to generate the standby voltage (+5VSB), as usual. A 2N60 is used, which has a maximum current of 8 A at 25° C.

Figure 7: Switching transistors.

The primary section from this power supply is controlled by a UC3845B PWM controller, which is located on a small printed circuit board, as you can see in Figure 6.

[nextpage title=”Secondary Analysis”]

This power supply uses six Schottky rectifiers on its secondary, using an unusual configuration for its +12 V output, as shown in Figure 8. As we could understand, the +12 V output "steals" current from the +5 V line.

Figure 8: Schematics for the secondary used on this power supply.

Let’s first analyze the +3.3 V output, which is the easiest one to understand. It uses two STPS2045CT Schottky rectifiers connected in parallel, with a maximum current limit of 20 A (10 A per internal diode, rated at 125° C). The maximum theoretical current the +3.3 V 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 (which in this case is made by two 10 A diodes in parallel). Just as an exercise, we can assume a typical duty cycle of 30%. This would give us a maximum theoretical current of 29 A or 94 W for the +3.3 V output. The maximum current this line can really deliver will depend on other components, in particular the coil used. Even though this power supply has separated rectifiers for its +3.3 V output, this output is generated from the same transformer output used for the +5 V output. Thus the maximum current +5 V and +3.3 V outputs can provide are limited by the maximum current this transformer output can provide.

The +5 V output is generated by two STPS4045CW Schottky rectifiers connected in parallel, each one with a maximum current limit of 40 A at 150° C (20 A per internal diode). The maximum theoretical current the +5 V output can deliver can be calculated using the same math. In this case we have two 20 A diodes in parallel, so the maximum theoretical current will be of 57 A or 286 W.

The +12 V output is generated by two BYW51-200 Schottky rectifiers connected in parallel, each one with a maximum current limit of 20 A at 120° C (10 A per internal diode). The maximum theoretical current the +12 V output can deliver can be calculated using the same math, but for the value of the diode we have to consider the path with the lower current limit. In this case this is the freewheeling path, i.e., the path where current flows when the diodes connected directly to the transformer are not conducting and energy is flowing from the coil. On this path we have the diode with an arrow in Figure 8 conducting, which has a 20 A limit (two 10 A diodes in parallel). This gives a maximum current of 29 A or 343 W for the +12 V output.

If our calculations are correct, it seems that this power supply uses components with values too close to the unit’s maximum labeled power. As explained unfortunately at this moment we don’t have a load tester yet, equipment that would say if this power supply can deliver or not its labeled power.

Figure 9: The six Schottky rectifiers used on the secondary (three on each side of the heatsink).

As we said earlier, the maximum power the power supply can deliver depends on other components used – like the transformer, coils, the PCB layout, the wire gauge and even the width of the printed circuit board traces.

This power supply uses Taiwanese electrolytic capacitors from OST. The big electrolytic capacitors from the passive PFC circuit is rated 85° C while all other smaller capacitors are rated at 105° C.

[nextpage title=”Power Distribution”]

In Figure 10, you can see GlacialPower GP-PS550BP label stating all its power specs.

Figure 10: Power supply label.

As you can see, the +5 V output is labeled as capable of delivering a maximum current of 25 A, what translates into 125 W, and the +3.3 V output is labeled as capable of delivering the same amount of current, 25 A, what translates into 82.5 W. This is below the maximum theoretical power we calculated in the previous page. However Glac
ialPower states the maximum combined power of the +3.3 V and +5 V outputs is of 130 W (and not 207.5 W, which is 125 W + 82.5 W). This happens because the +5 V and +3.3 V outputs are obtained from the same transformer output, as you can see in Figure 8.

As for the +12 V outputs, this power supply has two rails, +12V1 and +12V2, each one labeled as capable of delivering up to 18 A or 216 W. These rails, however, cannot deliver their maximum current/power at the same time – this happens with all power supplies. The combined limit for the +12 V outputs of this power supply is 400 W. This value is above the maximum theoretical current the +12 V can deliver, as calculated in the previous page.

The whole question regarding +12 V rails is the power distribution. The +12 V outputs – i.e., SATA drives, hard disk drives, main motherboard connector, ATX12V and VGA power cables – must be well balanced between the power supply’s rails, or the protection circuits will kick in even if the power supply isn’t delivering its maximum capable power.

On this power supply, for example, each +12 V rail can deliver up to 18 A. If your system pulls over 18 A (i.e., 216 W) on the power supply’s +12V1 output, it will shut down, even if are not using the +12V2 rail. In other words, the power supply will shut down at 216 W even though it is capable of delivering a combined 400 W on its +12V outputs (the over current protection is set at little higher level than what is announced on the product label, but let’s not consider this in the name of simplicity).

We think the power distribution on this power supply isn’t optimal, because the +12V2 rail is connected only to the ATX12V connector, while all other wires are connected to the +12V1 rail. So the +12V1 rail is obviously overloaded, especially because this power supply has two auxiliary PCI Express power connectors for two video cards.

This means that with this power supply you have a high chance of the power supply shutting down due to its over current protection while running a SLI or Crossfire configuration or even when using a single very high-end VGA, not because you have reached the power supply’s maximum power limit, but simply because of the power distribution across the +12V rails.

We think this power supply would have a better design if it had some other components connected to the +12V2 rail or if it had three rails, optimally with the main video card power connector connected to the third rail.

On the other hand GlacialPower says that this unit can deliver its labeled 550 W at 45° C, which is great. Usually power supply manufacturers label their units at 25° C, which is a shame: since the capability of delivering power shrinks with the temperature, usually you can’t achieve the labeled power under real-world conditions if you have a power supply labeled at 25° C.

Unfortunately we don’t have the necessary equipment to make a true power supply review; we would need to create a real 550 W load to check if this power supply could deliver its labeled power or not. In this First Look article we’d like to show only the internals of GlacialPower GP-PS550BP.

[nextpage title=”Main Specifications”]

GlacialPower GP-PS550BP power supply specs include:

• ATX12V 2.2
• Nominal labeled power: 550 W (labeled at 45° C).
• Efficiency: 78% at 230 V.
• PFC: Passive PFC.
• Motherboard Connectors: One 20/24-pin connector and one ATX12V connector.
• Peripheral Connectors: two PCI Express auxiliary power cables, one peripheral power cable containing two standard peripheral power connectors and one floppy disk drive power connector, one peripheral power cable containing three standard peripheral power connectors, and one Serial ATA power cable containing two SATA power connectors.
• Protections: short-circuit (SCP), over current (OCP), over voltage (OVP), over power protection (OPP) and over temperature (OTP).
• Warranty: Two years.
• More Information: https://www.glacialpower.com
• Maximum Suggested Retail Price (MSRP) in the US: USD 64.99

[nextpage title=”Conclusions”]

This product is clearly targeted to users that want a real 550 W power supply but don’t want to buy the most expensive models available on the market. Proof of that is that this power supply features passive PFC, which is a cheaper solution compared to active PFC.

The main drawback in using passive PFC is a lower efficiency compared to active PFC units: 78% against 80%+. This 78% efficiency, however, still puts this power supply way above “generic” power supplies with no PFC at all. A secondary drawback comes from the power supply weight: since passive PFC is based on a transformer, this power supply is heavier than units based on active PFC.

Unfortunately we don’t have a load tester yet, so we can’t say if this unit can really deliver its rated 550 W or not. Also because of that we can’t say anything about the unusual design used on its +12 V output.

This power supply features two +12V rails but in our opinion these two rails are not well distributed, since the second rail (+12V2) is used only by the ATX12V output. The first rail (+12V1) is, in our opinion, overloaded, since everything else (motherboard, video cards, hard disk drives, etc) is connected to it. The main problem of this configuration is that the over current protection (OCP) can kick in even though you haven’t reached this power supply’s maximum power. We think GlacialPower should have moved some of the outputs to the second rail (+12V2) or even used a three-rail design, putting the main video card power connector on the third rail.

We also think that the number of SATA connectors available on this power supply – only two – is simply not enough for today’s demands. It should have at least four.

As for the temperature, on the box and on GlacialPower’s website the manufacturer says this unit was labeled at 45° C. Why this is important? The higher the internal power supply temperature, the lower power it can deliver. Usually when no temperature is mentioned, the manufacturer assumes 25° C. You will never get 25° C inside a power supply; typical real-world values are found between 35° C and 40° C. So a power supply labeled at 25° C may not deliver its labeled power when running in the real world.

Is this a good product? Well, if you are trying to save some money and you are not building a high-end system it is an interesting choice – especially when you think that 550 W power supplies from well-known brands cost a lot more. But we think if you are building a SLI or Crossfire system or even a system using a very high-end single card there are options on the market that provide a better cost/benefit ratio, especially OCZ StealthXstream 600 W, even though this product from OCZ costs a little bit more.