Scythe Kamariki 4 550 W Power Supply Review

Primary Analysis

On this page we will take an in-depth look at the primary stage of Scythe Kamariki 4 550 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one GBU805 rectifying bridge in its primary, which can deliver up to 8 A at 100° C. At 115 V this unit would be able to pull up to 920 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 736 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.

Scythe Kamariki 4 550 W uses two SPP20N60C3 power MOSFET transistors on its active PFC circuit, each one capable of delivering up to 20.7 A at 25° C or 13.1 A at 100° C in continuous mode (note the difference temperature makes) or up to 62.1 A at 25° C in pulse mode, presenting a resistance of 160 mΩ when turned on, a characteristic called RDS(on). This number indicates the amount of power that is wasted, so the lower this number the better, as less power will be wasted thus increasing efficiency.

Figure 9: Rectifying bridge, active PFC transistors and diode.

The electrolytic capacitor in charge of filtering the active PFC output is Japanese from Chemi-Con and labeled at 105° C. This is great for two reasons. First Japanese capacitors have the best quality and don’t suffer from leakage and second it is better to see caps labeled at 105° C instead of 85° C.

This power supply uses another two SPP20N60C3 power MOSFET transistors on the traditional two-transistor forward configuration on its switching section. The specs for these transistors are published above.

Figure 10: Switching transistors.

The primary is controlled by a FAN4800I PFC/PWM controller.

Figure 11: PFC/PWM controller.