On this page we will take an in-depth look at the primary stage of MX-550. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.
This power supply uses one
GBU1006 rectifying bridge in 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.
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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.
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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).
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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.
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Figure 12: PFC/PWM controller.
