Component 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 50º 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, capacitors, 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 on its primary stage, which can deliver up to 15 A each (rated at 55º C with heatsink; the bridge used on this power supply wasn’t using a heatsink).

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 25º C) or 7 A (at 100º C) in continuous mode or 44 A (at 25º 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 25º C.

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

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Figure 7: Switching transistors.

This power supply uses six Schottky rectifiers on its secondary, using an unusual configuration for its +12 V output, as we shall see.
Two STPS4045CW connected in parallel are used for the +5 V output. Since each one has a maximum current of 40 A at 150º C, the +5 V output has a maximum theoretical current of 80 A or 400 W. Of course this is a theoretical number, because the maximum power depends on several other factors besides the rectifier, like the gauge of the wires, the width of the printed circuit board tracks, the transformer, the coils, the capacitors, etc.

Two STPS2045CT connected in parallel are used for the +3.3 V output. Since each one has a maximum current of 20 A (rated at 125º C), the +3.3 V output has a maximum theoretical current of 40 A or 132 W. 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 (for a better comprehension we present a simplified schematics on Figure 8).

And finally two BYW51-200 are used to generate the +12 V outputs. Here is what is strange about this power supply. Inside each Schottky rectifier there are two power diodes. Generally they are connected like the +3.3 V output shown on Figure 8. On this unit, however, the second diode from the +12 V output instead of being connected to ground it is hooked to the +5 V output (just follow the arrow we drew). This is the first time we’ve seen such configuration. We are not 100% sure why GlacialPower used this configuration. Each BYW51-200 is capable of rectifying up to 20 A at 120º C, thus in theory you are capable of pulling up to 40 A on the +12 V output, or 480 W.

On Figure 8 you can see a simplified schematics for the secondary used on this power supply. Each diode drawn on Figure 8 has another diode connected in parallel and we removed them from the schematics in the name of simplicity. On Figure 9 you can see the Schottky rectifiers (each one has two power diodes inside) and the thermal sensor used on this power supply. Keep in mind that for each output two rectifiers connected in parallel are used; the second rectifier is on the other side of the heatsink.

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

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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, capacitors, 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 85º C while all other smaller capacitors are rated at 105º C.

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