Primary Analysis
Contents
On this page we will take an in-depth look at the primary stage of the Huntkey X7 900 W. For a better understanding, please read our “Anatomy of Switching Power Supplies” tutorial.
This power supply uses one LL25XB60 rectifying bridge, which is attached to the same heatsink as the primary transistors. This bridge supports up to 25 A at 113° C, so in theory, you would be able to pull up to 2,875 W from a 115 V power grid. Assuming 80% efficiency, the bridge would allow this unit to deliver up to 2,300 W without burning itself out
. Of course, we are only talking about this particular component. The real limit will depend on all the components combined in this power supply.
Figure 11: Rectifying bridge
The active PFC circuit of the X7 models uses a design called interleaved, which works by having two active PFC circuits operating with a 180° phase-shift between them, i.e., when one is turned on, the other is turned off and vice-versa. The end-result is a lower ripple on the output voltage of the active PFC circuit. The heart of this circuit is the UCC28070 chip, which carries the two required PWM controllers and drives the two active PFC circuits, each one based on an FQA24N50 MOSFET, which is capable of delivering up to 24 A at 25° C or 15.2 A at 100° C in continuous mode (note the difference temperature makes), or up to 96 A in pulse mode at 25° C, each. This transistor presents a 200 mΩ resistance when turned on, a characteristic called RDS(on). The lower this number the better, meaning that the transistors will waste less power, and the power supply will achieve a higher efficiency.
Figure 12: Interleaved active PFC controller
The output of the active PFC circuits is filtered by one 470 µF x 450 V electrolytic capacitor and one 330 µF x 450 V electrolytic capacitor connected in parallel. This is the equivalent of one 800 µF x 450 V. Both capacitors are Japanese, from Chemi-Con, and labeled at 85° C.
In the switching section, the Huntkey X7 900 W also makes use of a very unique design: phase-shift full-bridge. This is the first time we’ve seen a PC power supply using such a design. It is implemented using a UCC38950 PWM controller that is connected to two IR2113S driver chips, each one activating two of the four required transistors. Another four FQA24N50 MOSFETs are used here, and the specifications for these components were already discussed above.
Figure 13: One of the active PFC diodes, one of the active PFC transistors, and two of the switching transistors
Figure 14: The other two switching transistors, the other active PFC transistor, and the other active PFC diode
Figure 15: The PWM controller and one of the drivers
Figure 16: The other driver
Let’s now take a look at the secondary of this power supply.