Let’s now take an in-depth look on the primary stage from AcBel Polytech iPoer 660. 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, each one supporting up to 6 A at 100º C, so the rectifying section can handle up to 12 A at 100º C. The bridges aren’t attached to a heatsink. This section is clearly overspec'ed: at 115 V this unit would be able to pull up to 1,380 W from the power grid; assuming 80% efficiency, the bridges would allow this unit to deliver up to 1,104 W without burning them. Of course we are only talking about this component and the real limit will depend on all other components from the power supply. Of course the lack of a heatsink would limit this maximum current.
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Figure 8: Rectifying bridges.
The active PFC circuit uses two FCPF11N60 power MOSFET transistors, which one capable of handling up to 7 A in continuous mode at 100º C (or 11 A at 25º C; see the difference temperature makes) or 33 A in pulse mode at 25º C. These transistors are located on the same heatsink as the switching transistors.
On the switching section this power supply uses another two FCPF11N60 power MOSFET transistors in the traditional two-transistor forward configuration.
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Figure 9: Active PFC transistor (left) and switching transistor (right).
The primary section of this power supply is controlled by a FAN4800 integrated circuit, which is a PFC/PWM controller combo.
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Figure 10: Active PFC/PWM controller combo.
