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 Huntkey.
The design used by this power supply is ridiculous, as it uses the same design as old AT and ATX power supplies: instead of using power MOSFET transistors on the switching section, it uses regular BJT transistors. The design used on the secondary is also old, as we will talk about on next page.
The main problem with this design is efficiency. FET transistors have high impedance, and the higher the impedance, the less power the component will draw from the circuit for its own operation – meaning less consumption and energy waste. Since this power supply uses regular transistors on its switching section, it is very unlikely that it can have high efficiency – and remember that Huntkey says that this power supply has 85% efficiency under full load! Of course we will check the power supply efficiency during our tests.
To be fair Seventeam ST-420BKV and Kingwin ABT-450MM use the same obsolete design but at these two power supplies can deliver their labeled power.
This power supply uses one D15XB80 rectifying bridge on its primary stage, which can deliver up to 3.2 A (rated at 25º C) without a heatsink installed, which was the case. If Huntkey had attached a heatsink to this bridge its maximum current would be 15 A. This is definitely something Huntkey should have done.
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Figure 9: Rectifying bridge.
On the switching section two FJP13009 NPN power transistors are used. They can deliver up to 12 A continuous mode or up to 24 A in pulse mode, which is the case. Both values are given at 25º C.
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Figure 10: Switching transistors (the second transistor is on the other side of the heatsink).
On Figure 11 you can find the schematics of a very old AT power supply. Huntkey Green Star 450 W uses this same basic schematics on both primary and secondary sections. This is simply ridiculous for a power supply being sold in 2008.
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Figure 11: Schematics of a very old AT power supply. This power supply uses this same design.
