Let’s now take an in-depth look on the primary stage from Green Star 350 W (LW-6350HG). For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one T15XB80 rectifying bridge on its primary, capable of delivering up to 15 A at 100º C if a heatsink is used – which is not the case – but only 3.2 A at 25º C if a heatsink is not used. The difference is outrageous and Huntkey should have added a heatsink on this component. The current limit for this component is simply too low (3.2 A).  At 115 V this unit would be able to pull only up to 368 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver only up to 294 W without burning this component. Of course we are only talking about this component and the real limit will depend on all other components from the power supply. This is the same component used on Huntkey V-Power 550 W and Huntkey Titan 650 W (Rocketfish 700 W), but at least Titan 650 W had a heatsink attached to it, which increased the current limit.

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Figure 8: Rectifying bridge.

LW-6350HG uses two FJP13009 power NPN transistors on its switching section using the half-bridge design, supporting up to 12 A in continuous mode or 24 A in pulse mode, both currents measured at 25º C (unfortunately the manufacturer from these transistors do not say how much they can deliver at higher temperatures). These are the same transistors used on Huntkey Green Star 400 W (Dynex 400 W) and Huntkey Green Star 450 W. Even though the transistors have the same specs on these other two power supplies they use a bigger packaging (called TO-247, while the packaging you can see on Figure 9 is called TO-220), which allow them to dissipate heat better.

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Figure 9: The two switching transistors.

The primary is controlled by an AZ7500B PWM controller, which is physically located on the secondary section of the power supply.

The two big electrolytic capacitors from the primary are from Teapo (a Taiwanese company) and rated at 85º C.