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, 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 55º 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 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), as usual. A 2N60 is used, which has a maximum current of 8 A at 25º C.

click to enlarge
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.