NCP1654_09 ONSEMI [ON Semiconductor], NCP1654_09 Datasheet - Page 14

• Manufacturer Part Number: NCP1654_09
• Description: Power Factor Controller for Compact and Robust, Continuous Conduction Mode Pre-Converters
• Manufacturer: ONSEMI [ON Semiconductor]

V
PFC modulation comparator,
V
I
C
V
the PFC modulation comparator.
switching frequency. Hence the charging current I
specially designed as in (Equation 5). The multiplier
voltage V
(Equation 6).
V
From (Equation 3) and (Equation 6), the input impedance
Z
the multiplier voltage V
the I
It is illustrated in Figure 34.
originally consists of a switching frequency ripple coming
from the inductor current I
inaccurately generated due to this ripple. This modulation
is the so−called “peak current mode”. Hence, an external
capacitor C
essential to bypass the high−frequency component of V
The modulation becomes the so−called “average current
mode” with a better accuracy for PFC.
ch
m
in
ramp
m
ramp
REF
I
Because V
It can be seen in the timing diagram in Figure 33 that V
ch
is the internal charging current,
+ V
is re−formulated in (Equation 7).
is the multiplier voltage appearing on V
L−50
, C
Figure 34. Multiplier Voltage Timing Diagram
is the internal reference voltage, the negative input of
is the internal ramp voltage, the positive input of the
is the internal ramp capacitor, and
V
REF
I
ramp
V
L
in
in order to have a constant Z
M
m
M
I
*
in
, and V
REF
is therefore expressed in terms of t
connected to the multiplier voltage V
C
ramp
t
and V
1
Z
I
C
REF
ch
in
ramp
out
+
+
m
T
also act as the ramp signal of
are roughly constant versus time,
is designed to be proportional to
V
V
C
V
REF
REF
ramp
m
L
T
. The duty ratio can be
+ V
V
I
V
L*50
REF
out
REF
in
T * t
for PFC purpose.
T
m
1
pin,
Time
Time
Time
m
http://onsemi.com
(eq. 5)
(eq. 6)
(eq. 7)
pin is
ch
1
m
in
is
m
.
14
(Equation 8).
Where,
R
which is constant.
V
which is proportional to the rms input voltage,
I
I
V
Operational Trans−conductance Amplifier (OTA), as
described in (Equation 12).
and hence its value affects the NCP1654 to operate in either
“follower boost mode” or “constant output voltage mode”.
Refer to Figure 36,
where
V
K
<V
appearing on C
V
cs
L
Figure 36. External Connection on the Brown Out Pin
V
M
ac
bo
control
bo
BO
The multiplier voltage V
R
m
as described in (Equation 11).
in
is the sense current proportional to the inductor current
Figure 35. External Connection on the Multiplier
M
is the external multiplier resistor connected to V
is the RMS input voltage.
+
is the voltage on BO pin.
is the input voltage signal appearing on the BO pin,
> is the average voltage signal of V
is the decay ratio of V
R
directly limits the maximum input power capability
V
4(V
boL
is the control voltage signal, the output voltage of
in
control
V
V
K
Modulation
PFC Duty
m
bo
BO
R
filter
R
* V
boU
+
+ K
M
+
I
4(V
cs
.
C
CONTROL(min)
R
BO
V
BO
boU
bo
control
Voltage Pin
Vbo
4
(V
R
) R
in
boL
) + K
in
R
* V
m
M
to V
boL
V
V
I
is generated according to
cs
+
-
boH
boH
)
CONTROL(min)
BO
V
bo
bo
/ V
= 1.3 V, V
@
.
V
BO
boL
2 2
m
p V
2
in
boL
ac
R
)
, the voltage
I
m
M
= 0.7 V
(eq. 10)
(eq. 8)
(eq. 9)
C
+
m
M
pin,