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## Primary Analysis

On this page we will take an in-depth look at the primary stage of the FSP Aurum CM Gold 750 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one GBU15L06 rectifying bridge, which is attached to an individual heatsink. This bridge supports up to 15 A at 115° C, so in theory, you would be able to pull up to 1,725 W from a 115 V power grid. Assuming 80% efficiency, the bridge would allow this unit to deliver up to 1,380 W without burning itself out. Of course, we are only talking about this component, and the real limit will depend on all the other components in this power supply. The Aurum Gold 700 W uses a similar bridge here.

Figure 10: Rectifying bridge

The active PFC circuit uses two IPB60R165CP MOSFETs, which are capable of delivering up to 21 A at 25° C or 13 A at 100° C in continuous mode (note the difference temperature makes), or up to 61 A in pulse mode at 25° C, each. These transistors present a 165 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. These are the same transistors used in the FSP Aurum Gold 700 W.

The capacitor used to filter the output of the active PFC circuit is Japanese, from Rubycon, and labeled at 105° C.

In the switching section, FSP decided to use a very unique design, called active clamp reset forward, and it seems that FSP put a lot of effort in developing this design. The switching transistor is an SPA17N80C3 MOSFET, which is capable of delivering up to 17 A at 25° C or 11 A at 100° C in continuous mode (note the difference temperature makes), or up to 51 A at 25° C in pulse mode. This transistor presents a 290 mΩ RDS(on). A second transistor (resetting transistor) is used to turn off the switching transistor and is controlled from the secondary side. The transistor used for this function is an FQPF3N80C. This is exactly the same configuration used in the FSP Aurum Gold 700 W.

Figure 11: Switching transistor, resetting transistor, active PFC diode and active PFC transistors

The primary is managed by a custom-made PFC/PWM controller called FSP6600. Since this is a custom integrated circuit, no datasheet is available for it.

Figure 12: Active PFC/PWM combo controller

Let’s now take a look at the secondary of this power supply.

## Contents

Gabriel Torres is a Brazilian best-selling ICT expert, with 24 books published. He started his online career in 1996, when he launched Clube do Hardware, which is one of the oldest and largest websites about technology in Brazil. He created Hardware Secrets in 1999 to expand his knowledge outside his home country.