Vivanco UNIVERSAL SWITCHMODE AC TO DC MAINS ADAPTERS WITH USB CHARGING FUNCTION Podręcznik Użytkownika Pobierz pdf (Strona 16)

SMPS AC/DC Reference Design User’s Guide

FIGURE 1-6: BUCK PFC INPUT CURRENT SHAPE

1.2.1.2.2 Boost PFC Circuit

The Boost converter produces a voltage higher than the input rectified voltage;

therefore, the switch (MOSFET) rating should be rated higher than V

OUT. Figure 1-7

shows the circuit for the Boost PFC stage. Figure 1-8 shows the Boost PFC input

current shape.

FIGURE 1-7: BOOST PFC

FIGURE 1-8: BOOST PFC INPUT CURRENT SHAPE

1.2.1.2.3 Buck/Boost PFC Circuit

In the Buck/Boost PFC circuit, the output DC voltage may be either less or greater than

the input rectified voltage. High Power Factor can be achieved in this case. The switch

(MOSFET) is rated to (V

IN + VOUT). Figure 1-9 shows the circuit for the Buck/Boost

PFC stage. Figure 1-10 shows the Boost PFC input current shape.

Input Current

Input Voltage

Input Current

Input Voltage

1 2 ... 11 12 13 14 15 16 17 18 19 20 21 ... 117 118

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Vivanco UNIVERSAL SWITCHMODE AC TO DC MAINS ADAPTERS WITH USB CHARGING FUNCTION Podręcznik Użytkownika Strona 16