OCZ Z Series 1000 W Power Supply Review

Primary Analysis

On this page we will take an in-depth look at the primary stage of OCZ Z Series 1000 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses two GBJ2506 rectifying bridges connected in parallel in its primary, each one supporting up to 25 A at 100° C with a heatsink is used, which is the case (without a heatsink this limit drops to 4 A). At 115 V this unit would be able to pull up to 5,750 W from the power grid; assuming 80% efficiency, the bridges would allow this unit to deliver up to 4,600 W without burning themselves out
. ¡ay caramba! Talk about overspecification! Of course, we are only talking about these components, and the real limit will depend on all the other components in this power supply. These components were upgraded from the 850 W version, which uses two 15 A bridges here.

Figure 9: Rectifying bridges.

On the active PFC circuit three SPW24N60C3 power MOSFET transistors are used, each one capable of delivering up to 24.3 A at 25° C or 15.4 A at 100° C in continuous mode (note the difference temperature makes), or up to 72.9 A in pulse mode at 25° C. These transistors present 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. This section was upgraded from the 850 W version, which uses only two transistors instead of three.

Figure 10: Active PFC transistors.

This power supply uses two electrolytic capacitors to filter the output from the active PFC circuit. The use of more than one capacitor here has absolute nothing to do with the “quality” of the power supply, as laypersons may assume (including people without the proper background in electronics doing power supply reviews around the web). Instead of using one big capacitor, manufacturers may choose to use two or more smaller components that will give the same total capacitance, in order to better accommodate space on the printed circuit board, as two or more capacitors with small capacitance are physically smaller than one capacitor with the same total capacitance. OCZ Z Series 1000 W uses two 390 µF x 400 V capacitors in parallel; this is equivalent of one 780 µF x 400 V capacitor. These capacitors are Japanese, from Rubycon and labeled at 105° C, the best configuration possible.

In the switching section, another two SPW24N60C3 power MOSFETs are used on the traditional two-transistor forward configuration. The specs for these transistors are published above. These are the same transistors used on the 850 W model.

Figure 11: Switching transistors.

The switching transistors are controlled by the famous PFC/PWM combo controller CM6800. This was a surprise, as we didn’t expect an 80 Plus Gold using this controller, as many other manufacturers are moving to other designs in order to increase efficiency (e.g., resonant design).

Figure 12: PFC/PWM combo controller.

In summary on the 1000 W model the bridges were upgraded and one additional transistor was added  on the active PFC circuit in relation with the 850 W model.

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