DocID023523 Rev 2

3/43

AN4149

List of figures

List of figures

Figure 1.

Line and inductor currents in CCM PFC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Figure 2.

Line and inductor currents in TM PFC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Figure 3.

Block diagram of an FOT-controlled PFC preregulator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Figure 4.

Line-modulated FOT modulator internal block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Figure 5.

Line-modulated FOT modulator key waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Figure 6.

Boundary between DCM and CCM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Figure 7.

Typical frequency change along a line half-cycle in a boost PFC operated in LM FOT . . . . 8

Figure 8.

Typical frequency change along a line half-cycle in a boost PFC operated in TM . . . . . . . . 8

Figure 9.

LM FOT controlled boost PFC: current waveforms (line current) . . . . . . . . . . . . . . . . . . . . . 8

Figure 10.

LM FOT controlled boost PFC: current waveforms (boost inductor current envelope). . . . . 8

Figure 11.

Line-modulated, FOT controlled boost PFC: input current harmonic contents . . . . . . . . . . . 9

Figure 12.

Total MOSFETs losses in the 350 W FOT PFC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Figure 13.

Multiplier characteristics family for VFF = 1 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 14.

Multiplier characteristics family for VFF = 3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 15.

Small signal model of a PFC stage with a constant-power load (DC-DC converter) . . . . . 30

Figure 16.

Bode plots of the control-to-output transfer function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Figure 17.

Schematic diagram of a type II compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Figure 18.

Bode plots of a type II amplifier's transfer function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Figure 19.

Bode plots of the closed-loop transfer function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Figure 20.

115 Vac step load (50 % to 100 %): improper compensation . . . . . . . . . . . . . . . . . . . . . . . 36

Figure 21.

115 Vac step load (50 % to 100 %): good compensation . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Figure 22.

EVL4984-350W PCB layout (SMT side view). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Figure 23.

Excel spreadsheet design specification input table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Figure 24.

Other design data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Figure 25.

CCM PFC schematic based on the L4984D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Figure 26.

Excel spreadsheet BOM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40