Primary Analysis

Let’s now take an in-depth look on the primary stage from Cooler Master eXtreme Power Plus 460 W (RS-460-PMSR-A3). For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses two GBU605 rectifying bridges connected in parallel on its primary stage. Each bridge can deliver up to 6 A (rated at 100º C), for a total of 12 A at 100º C. This stage is clearly overspec’ed, as power supplies from this power range usually use only one 6 A or 8 A bridge. The bridges don’t use a heatsink.

click to enlarge
Figure 8: Rectifying bridges.

On the switching section this power supply uses two 2SK2749 power MOSFET transistors in parallel in a single-transistor forward configuration. Most modern power supplies use a different configuration, two-transistor forward, which is more efficient. Each 2SK2749 can drive up to 7 A in continuous mode or up to 21 A in pulse mode (which is the mode used), so the maximum current the switching section can drive is 14 A in continuous mode or 42 A in pulse mode. All values were measured at 25º C.

click to enlarge
Figure 9: Switching transistors.

Total or partial reproduction of the contents of this site, as well as that of the texts available for downloading, be this in the electronic media, in print, or any other form of distribution, is expressly forbidden. Those who do not comply with these copyright laws will be indicted and punished according to the International Copyrights Law.

We do not take responsibility for material damage of any kind caused by the use of information contained in Hardware Secrets.