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 Thermaltake.

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.

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, capacitors, the PCB layout and the wire gauge – 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 GBJ1506 rectifying bridge on its primary stage, which can deliver up to 15 A (rated at 100º C).

Four power MOSFET transistors are used on this power supply primary, two on the active PFC circuit and two on the switching section. On the active PFC circuit two 20N60C3 are used, see Figure 16. These transistors have a maximum rated current of 45 A each.

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Figure 16: Rectifying bridge (on the left) and active PFC transistors (on the right) used on this power supply.

On the switching section two IRFP460A power MOSFET transistors in two-transistor forward switcher configuration are used, and each one has a maximum rated current of 80 A in pulse mode, which is the mode used, as the PWM circuit feeds these transistors with a square waveform. In continuous mode they can deliver up to 20 A @ 25º C or up to 13 A @ 100º C. As you may have noticed we are now publishing the temperature spec of each component, as this will play a major role on our analysis. As you can see, the higher the temperature, the lower current semiconductors can deliver. We will discuss more about this later.

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Figure 17: The two switching transistors. On the other side of this heatsink is the PFC diode.

For a better understanding on the relationship between these transistors, we drew a simplified diagram of this section of Toughpower 750 W power supply, see Figure 18.

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Figure 18: Simplified diagram of this power supply showing the location of its four MOSFET transistors.

On Figure 19 you can see the four power Schottky rectifiers used on the secondary section and also the thermal sensor located on the secondary heatsink.

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Figure 19: Power rectifiers used on the secondary.

The +12 V output is produced by two STPS60L45CW Schottky rectifiers connected in parallel, which can deliver up to 60 A each (measured at 135º C), thus the maximum theoretical current the +12 V line can deliver is of 120 A, which equals to 1,440 W. The maximum current this line can really deliver will depend on other components, especially the transformer, the coil, the capacitor and the wire gauge used.

The +5 V output is produced by one STPS40L45CW Schottky rectifier, supporting up to 40 A (measured at 130º C). This equals to 200 W. Of course the maximum current this line can really deliver will depend on other components, especially the transformer, the coil, the capacitor and the wire gauge used, as mentioned before.

The +3.3 V output is also produced by another STPS40L45CW Schottky rectifier, supporting up to 40 A (measured at 130º C). This equals to 132 W. Of course the maximum current this line can really deliver will depend on other components, especially the transformer, the coil, the capacitor and the wire gauge used, as mentioned before.

Even though the +5 V line and the +3.3 V line have separated rectifiers, they share the same transformer output. So the maximum current both lines can deliver will depend a lot on the transformer.

This power supply +5VSB output (a.k.a. “standby power”) uses a SBL1040CT Schottky rectifier, which can deliver up to 10 A (measured at 95º C). This equals to 50 W, not bad at all. Once again, the real maximum power will depend on the other components used.