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 Tagan – especially because we are talking about a power supply labeled over 1,000 watts.

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

This power supply uses two GBU1006 rectifying bridges on its primary stage, which can deliver up to 10 A each (rated at 100º C), so the total current the rectifying section of this power supply can handle is of 20 A. Just for a comparison, Enermax Galaxy 1000 W uses two 20 A bridges, meaning it can handle the double: 40 A.

The active PFC circuit from this power supply uses three power MOSFET transistors (20N60C3 – the same one used by several other power supplies we took a look, like Antec Neo 550 HE, Cooler Master iGreen Power 430 W, Corsair HX620W, Thermaltake Toughpower 750 W, OCZ GameXstream 700 W and Zalman ZM600-HP). This power supply from Tagan, Zalman ZM600-HP and OCZ GameXstream 700 W are the only three power supplies we’ve seen using such design. All other high-end power supplies we’ve seen to date use only two transistors (except Enermax Galaxy 1000 W, which uses four transistors). Each 20N60C3 can handle up 300 A @ 25º C each in pulse mode (which is the case).

Instead of using only one electrolytic capacitor on its active PFC circuit, this power uses two 1,200 µF x 200 V connected in series, which equals to a 600 µF x 400 V capacitor. On other power supplies we’ve seen the active PFC circuit have values below that, typically 470 µF and even 165 µF on Enermax Galaxy 1000 W (which uses two 330 µF x 450 V in parallel). The electrolytic capacitors used here are Japanese from Toshin Kogyo (TK), but the electrolytic capacitors found on the secondary are Taiwanese from Teapo.

The active PFC components (PFC coil, PFC diode and NTC thermistor) from this power supply are placed in a different order compared to the most usual configuration. In order to clarify this, we drew the schematics of this power supply active PFC circuit and compare it to the most common design on Figure 21.

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Figure 21: Active PFC.

This power supply uses four 20N60C3 power MOSFET transistors on its switching section, the same type used on the active PFC circuit. Without looking to this power supply circuit, we though that Tagan used the same design Enermax did on their Galaxy 1000 W: two transistors driving each transformer, making two completely separated primary and secondary circuits. However, looking carefully to the circuit, we found out that Tagan (or better, Topower) decided to use a design that, well, we wouldn’t use if we were their engineers.

For a better understanding of what we are going to explain, we drew a simple block diagram of what we think would be a good design for a 1,000 W+ power supply (in fact, the same design used by Enermax Galaxy 1000 W) and the design used by Tagan TurboJet 1100 W. Please pay careful attention on Figure 22.

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Figure 22: Design used by Tagan TurboJet TG1100-U95.

On our recommended design, there are two complete independent primary and secondary circuits, as if there were two complete power supplies inside the unit housing. In fact the only thing these two circuits share are the +Bus and –Bus power lines coming from the active PFC circuit. This design is the only one that can truly deliver over 1,000 watts of power.

On Tagan TurboJet TG1100-U95 there is only one switcher. Even tough there are four transistors, two of them are connected in parallel to the other two just to increase the current/power this single switcher can deliver (the design of the switcher, by the way, is two-transistor forward). What is ironic is that in terms of cost the two designs cost the same!

So even though this power supply from Tagan has two transformers, they are not independent, as the same transistors drive them.

But what is really bad about this unit is the design Topower chose to use on its secondary. As you can see, this power supply has only one +12 V filtering stage. So the output of all +12 V rectifiers are connected together and then filtered by only two coils (one big and another small) and three electrolytic capacitors. As we mentioned exhaustively in previous articles, the coils and capacitors are the main components that limit the maximum power the power supply can deliver, as the rectifiers are usually very overspec’ed. And based on the size of the coils and electrolytic capacitors found here we can say for sure that this power supply simply cannot deliver the 960 W labeled by Tagan for its +12 V combined power. This power could only be achieved if this power supply used two independent +12 V filtering sections.

We don’t have a load tester, but our friends at Planet3Dnow.de have one (a Chroma 8000). They tested this Tagan power supply at 25º C and it burned when they tried to pass over 768 W on the +12 V lines. Their conclusion was that this power supply has something wrong with the +12 V outputs, and the explanation is right above. Just for the record, they tested Galaxy 1000 W from Enermax on the same review and it could deliver up to 1,050 W at 50º C, which is really impressive.