Gigabyte Superb 550P Power Supply Review

Primary Analysis

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

This power supply uses two GBU605 rectifying bridges connected in parallel. Each one supports up to 6 A at 100° C if a heatsink is used, which is not the case. At 115 V this unit
would be able to pull up to 1,380 W from the power grid; assuming 80% efficiency, the bridges would allow this unit to deliver up to 1,104 W without burning themselves out. Of course we are only talking about this component and the real limit will depend on all other components from the power supply.

Figure 11: Rectifying bridges.

The capacitors from the voltage doubler circuit are Japanese from Chemi-Con and labeled at 105° C, a miracle on a power supply without active PFC.

This unit is based on the single-transistor forward topology, using two 2SK2749 power MOSFET transistors connected in parallel on its switching section in order to double the maximum current supported by this stage. Each transistor can deliver up to 7 A at 25° C in continuous mode, or up to 21 A at 25° C in pulse mode (unfortunately the manufacturer doesn’t specify the maximum currents at 100° C). These transistors have a maximum RDS(on) of 1.6 Ω, which is insanely high, meaning they have low efficiency (the higher this number, the lower the efficiency). Wait a minute, wasn’t Gigabyte the first manufacturer to promote the advantages of using transistors with low RDS(on) on their motherboards? Surreal…

Figure 12: One of the switching transistors.

The switching transistors are controlled by a UC3843B PWM controller, which is physically located on the primary from the power supply.

Figure 13: PWM controller.

Now let’s take a look at the secondary of this power supply.