bequiet! Straight Power E9 CM 680 W Power Supply Review

Primary Analysis

On this page we will take an in-depth look at the primary stage of the bequiet! Straight Power E9 CM 680 W. For a better understanding, please read our “Anatomy of Switching Power Supplies” tutorial.

This power supply uses two GBU1006 rectifying bridges, which are attached to an individual heatsink. Each bridge supports up to 10 A at 100° C, so in theory, you would be able to pull up to 2,300 W from a 115 V power grid. Assuming 80% efficiency, the bridges would allow this unit to deliver up to 1,840 W without burning themselves out. Of course, we are only talking about this particular component. The real limit will depend on all the components combined in this power supply. It is interesting to note that both the FSP Aurum Gold 700 W and the Aurum CM Gold 750 W use only one of these bridges here.

Figure 10: Rectifying bridges

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 and the Aurum CM Gold 750 W.

The output of the active PFC circuit is filtered by a 390 µF x 420 V electrolytic capacitor from CapXon, labeled at 85° C. The two FSP models to which we are comparing this unit use Japanese capacitors labeled at 105° C.

In the switching section, the bequiet! Straight Power E9 CM 680 W uses FSP’s design of choice for 80 Plus Gold units, called active clamp reset forward. 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 and the Aurum CM Gold 750 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 controller

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