Let’s now take an in-depth look on the primary stage from MX-550. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.
This power supply uses one
GBU1006 rectifying bridge on its primary, capable of delivering up to 10 A at 100º C if a heatsink is used, which is the case. This is more than adequate rating for a 500 W power supply. The reason why is that at 115 V this unit would be able to pull up to 1,150 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 920 W without burning this component. Of course we are only talking about this component and the real limit will depend on all other components from the power supply.
click to enlarge
Figure 9: Rectifying bridge.
MX-550 uses two SPP16N50C3 power MOSFET transistors on its active PFC circuit, each one capable of delivering up to 10 A at 100º C (or 16 A at 25º C, see the difference temperature makes) in continuous mode or up to 48 A in pulse mode.
The active PFC capacitor is Japanese from Matsushita (Panasonic) and labeled at 85º C.
click to enlarge
Figure 10: Active PFC transistors and diode.
This power supply uses two SPA16N50C3 power MOSFET transistors on the traditional two-transistor forward configuration on its switching section. These transistors are identical to the ones used on the active PFC circuit except for the packaging (TO220 vs. TO220FP).
click to enlarge
Figure 11: Switching transistors.
The primary is controlled by a CM6800 integrated circuit installed on a small printed circuit board. This component is the most popular PWM/PFC combo controller.
click to enlarge
Figure 12: PFC/PWM controller.
