Tagan TurboJet TG1100-U95 1,100 W Power Supply

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 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 in its primary stage, which can deliver up to 10 A each (rated at 100° C), so the total current the rectifying section of this power supply can handle is of 20 A. This is more than adequate rating for a 1,000 W power supply. The reason why is that at 115 V this unit would be able to pull up to 2,300 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 1,840 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. 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 Ga
meXstream 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 @ 25° 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. When two identical capacitors are connected in series, their capacitance is halved, but the voltage limit is doubled. This is a common trick used to reduce the space needed inside the power supply, as capacitors with higher voltages are physically bigger. The electrolytic capacitors used here are from Toshin Kogyo (TK) – even tough this brand is Japanese, their capacitors are rebranded OST (Taiwanese) components – and the electrolytic capacitors found on the secondary are also 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 in Figure 19.

Figure 19: 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, 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).

On Figures 20 and 21 you can see the components that are attached to the primary heatsink. As mentioned, even though there are four power MOSFET transistors (labeled Q4 through Q7), Q4 and Q5 are connected in parallel, as it is Q6 and Q7.

Figure 20: Rectifying bridges, active PFC transistors and active PFC diode.

Figure 21: Switching transistors and rectifying bridges.

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 in Figure 22.

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.

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

The primary is controlled by one CM6800 integrated circuit, which is an active PFC and PWM controller combo. It is located on a small printed circuit board shown in Figure 23. This is the same controller used by several other power supplies, like OCZ GameXstream 700 W, Zalman ZM600-HP, Antec Neo HE 550 and Thermaltake Toughpower 750 W, just to name a few.

Figure 23: Active PFC and PWM controller integrated circuit.