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 HEC.

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 GBU806 rectifying bridge on its primary stage, which can deliver up to 8 A (rated at 100º C). No heatsink was used to cool down this component.

On the switching section two 2SK2749 power MOSFET transistors are used under a modified single-transistor forward configuration. Usually this configuration uses only one transistor, but on this power supply two transistors were connected in parallel in order to double the maximum current.

Each one has a maximum rated current of 21 A @ 25º C in pulsating mode, which is the mode used, as the PWM circuit feeds these transistors with a square waveform.

If you pay close attention on Figure 11 you will see a small copper plate between the transistors and the aluminum heatsink, put there to improve heat dissipation.

click to enlarge
Figure 11: MOSFET transistors used on the primary.

On Figures 12 and 13 you can see the four power Schottky rectifiers used on the secondary section of this power supply. As you can see, a copper plate is used between the +5 V rectifier and the heatsink in order to provide a better heat dissipation.

click to enlarge
Figure 12: Power rectifiers used on the secondary.

click to enlarge
Figure 13: Power rectifiers used on the secondary.

The +12 V output is produced by two MBR20100CT Schottky rectifiers, which can deliver up to 20 A each (measured at 133º C), thus the maximum theoretical current the +12 V line can deliver is of 40 A, which equals to 480 W. The maximum current this line can really deliver will depend on other components, especially the transformer, the coil, the capacitor, the wire gauge and even the width of the printed circuit board traces used.

The +5 V output is produced by one MBR6045PT Schottky rectifier, supporting up to 60 A (measured at 125º C). This equals to 300 W. Of course the maximum current this line can really deliver will depend on other components, especially the transformer, the coil, the capacitor, the wire gauge and even the width of the printed circuit board traces used, as mentioned before.

Here we found something different from other power supplies with no PFC we’ve seen so far. Usually the +3.3 V output on low-end power supplies is done by a 3.3 V voltage regulator connected to the +5 V output. This power supply from HEC, however, uses the same design as high-end power supplies, using an independent Schottky rectifier for producing its +3.3 V output. Even more: on this power supply we could notice a place for installing a second rectifier in parallel, doubling the amount of current supported by the +3.3 V output. This configuration is probably used by another power supply manufactured by HEC based on the same PCB used by WinPower 480 W.

The +3.3 V output is produced by another MBR6045PT Schottky rectifier, supporting up to 60 A (measured at 125º C). This equals to 198 W. Of course the maximum current this line can really deliver will depend on other components, especially the transformer, the coil, the capacitor, the wire gauge and even the width of the printed circuit board traces 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 uses Taiwanese electrolytic capacitors from Teapo and CapXon. The two big capacitors from the voltage doubler are rated 85º C while all other smaller capacitors are rated 105º C.