NCL30051LEDGEVB ON Semiconductor, NCL30051LEDGEVB Datasheet - Page 9

• Manufacturer Part Number: NCL30051LEDGEVB
• Description: Power Management IC Development Tools 90-265VAC 60W ISO CC EVB
• Manufacturer: ON Semiconductor
• Type: Power Factor Correctionr

Specifications of NCL30051LEDGEVB

• Rohs: yes
• Product: Evaluation Boards
• Tool Is For Evaluation Of: NCL30051
• Input Voltage: 90 VAC to 265 VAC
• Output Voltage: 35 V to 50 V
• Output Current: 1.5 A

PFC Choke Design (L2)
ON Semiconductor Application Note AND8123, we can
analyze the PFC choke design.
Inductor rms current at 50 W output and 85 Vac input:
0.72 A
Inductor peak current at 50 W out and 85 Vac input: 1.75 A
Maximum inductance for reasonable switching frequency:
1200 mH max.
Turns ratio to aux winding to produce a 15 to 18 Vdc V
9:1 or 10:1
core was also selected for the PFC choke. Based on an rms
choke current of 0.72 A and an average switching frequency
of around 100 kHz, three strands of AWG #30 magnet wire
was chosen for the main winding to minimize ac losses.
Calculations based on the approximate wire diameter (2 x
0.012” or 0.61 mm), and a core bobbin inside winding width
of about 0.47” (12 mm); it appears that 75 turns of this wire
can comfortably be wound on 4 or 5 layers with about 18
turns per layer. Using the above parameters from the design
spreadsheet, and the following inductor relationships we can
determine the optimum design using this PQ−2020 core:
Using the PFC design approach illustrated in
To maintain component consistency, a PQ−2020 ferrite
http://onsemi.com
CC
:
9
Where:
75 turns, B
get L = 770 mH which is less than the max of 1200 mH. This
will result in a switching frequency of 70 kHz min and
200 kHz max for typical operation, so this is probably a
reasonable inductance to start with. We could increase the
inductance and lower the PFC switching frequency by
adding more turns, but this would probably require a larger
core.
the second equation. Substituting in the known parameters
we get Lg = 0.055 cm or 0.022 inches. Since this is the total
gap, we would use half of this length if we were gapping all
three pole legs of the core. This gap should also give us the
required inductance of about 700 mH. The final choke
design is shown in Figure 5.
Substituting the known values into first equation for N =
In order to prevent saturation, the core must be gapped per
L +
max
N
Ipk
= 3000 gauss, Ae = 0.6, and Ipk = 1.75 A we
N is the number of turns
B
Ipk is the peak inductor current
Ae is the core cross sectional area (cm
Lg is the total core gap (cm)
B
max
max
10
is the max flux density
8
Ae
and Lg +
0.4p
B
max
N
Ipk
2
)