ncp1910 ON Semiconductor, ncp1910 Datasheet - Page 20

• Manufacturer Part Number: ncp1910
• Description: Ncp1910 High Performance Combo Controller For Atx Power Supplies
• Manufacturer: ON Semiconductor

PFC Methodology
particularly designed for CCM operation. The PFC
methodology is described in this section.
switching period T includes a charging phase for duration t
and a discharging phase for duration t
conversion ratio is obtained in Equation 1.
Where:
The NCP1910 uses a proprietary PFC methodology
As shown in Figure 42, the inductor current I
♦
V
bulk
Figure 42. Inductor Current in CCM
is the output voltage of PFC stage,
V
V
bulk
V
in
in
+
+
t
T * t
1
) t
t
T
2
V in
1
2
V
+
bulk
I in
T * t
T
1
Figure 41. CCM PFC Boost Converter
C in
R SENSE
2
. The voltage
L
L
(eq. 1)
http://onsemi.com
I L
in a
1
20
filter absorbs the high−frequency component of inductor
current I
signal only of the inductor current.
Where:
formulated.
where: Z
Equation 3 is constant or varies slowly in the 50 or 60 Hz
bandwidth.
The input filter capacitor C
From Equations 1 and 2, the input impedance Z
Power factor is corrected when the input impedance Z
♦
♦
♦
♦
♦
♦
♦
means it is with a 50 Hz bandwidth of the original
I
V
T is the switching period,
t
t
I
I
I
1
2
L
in
L
L−50
in
.
is the MOSFET on time, and
is the MOSFET off time.
is the inductor current.
L
is the input AC current.
in
is the rectified input voltage,
. It makes the input current I
is input impedance.
supposes a 50 Hz operation. The suffix 50
C bulk
Z
in
+
Bulk voltage (V
V
I
I
in
in
in
+
+ I
T * t
in
L−50
T
and the front−ended EMI
bulk
1
)
I
V
L*50
bulk
in
a low−frequency
(eq. 2)
(eq. 3)
in
in
in
is