NCP1611ADR2G ONSEMI [ON Semiconductor], NCP1611ADR2G Datasheet - Page 22

• Manufacturer Part Number: NCP1611ADR2G
• Description: Enhanced, High-Efficiency Power Factor Controller
• Manufacturer: ONSEMI [ON Semiconductor]

In some cases, the system enters then the dead−time (t
lasts until the next clock is generated.
Figure 8, the MOSFET on−time t
V
as follows:
mentioned, it is 3 times higher at high line compared to its
value at low line). C
transformed into a signal (V
1 V. (V
section to modulate the MOSFET duty−cycle. The
NCP1611 includes some circuitry that processes (V
to form the signal (V
Figure 9). (V
sensed during the precedent current cycles, that is, for a
proper shaping of the ac line current. This modulation leads
to:
or
(V
Hence, the (V
Provided that in addition, (t
Equation 1 leads to: (I
More exactly:
V
REGUL
ton
I
where : k + constant +
One can show that the ac line current is given by:
The NCP1611 operates in voltage mode. As portrayed by
The charge current is constant at a given input voltage (as
The output of the regulation block (V
Given the low regulation bandwidth of the PFC systems,
CONTROL
Where t
in
+ k @ V
generated by the regulation block and an internal ramp
REGUL
is at its (V
on
) and then (V
in
,
max
ton
ton
) is the voltage that is injected into the PWM
) is modulated in response to the dead−time
• (t
V
is the maximum on−time obtained when
I
ton
in
1
V
ton
ramp
t
+ V
+ t
1
ton
@
Figure 64. PFC Boost Converter (left) and Inductor Current in DCM (right)
) that is used in the PWM section (see
in
+
REGUL
2
t
1
+
) / T) term is substantially constant.
REGUL
= k • V
is an internal capacitor.
in
) t
C
T
T @ V
ramp
REGUL
t
2L
2
1
1
)
t
1
1
max
I
+ V
) is proportional to (V
t
ch
) are slow varying signals.
2TL
1
) t
@
@ V
1
REGUL
in
) t
is controlled by the signal
), where k is a constant.
) varying between 0 and
V
REGUL
2
ton
maximum level. The
V
REGUL max
2
REGUL
CONTROL
@ t
) is linearly
on,max
REGUL
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(eq. 1)
(eq. 2)
(eq. 3)
3
) that
ton
),
)
22
the ac line rectified voltage.
proportional to V
parametric table shows that t
(T
(when pin2 happens to exceed 2.2 V with a pace higher than
40 Hz – see BO 25 ms blanking time).
Hence, the ac line current is properly shaped.
case. This condition is just a particular case of this
functioning where (t
(V
adapts to the conditions and transitions from DCM and CrM
(and vice versa) without power factor degradation and
without discontinuity in the power delivery.
Hence, we can re−write the above equation as follows:
at low line.
at high line.
From these equations, we can deduce the expression of the
average input power:
at low line
at high line
Where (V
I
I
Where T = (t
In light of this equation, we immediately note that I
The input current is then proportional to the input voltage.
One can note that this analysis is also valid in the CrM
ON(LL)
in
in
TON
+
+
=V
V
V
in
in
) at low line and to 8.3 ms (T
REGUL
P
REGUL
P
@ T
@ T
2 @ L
2 @ L
in,avg
in,avg
ON(LL)
ON(HL)
1
+ t
). That is why the NCP1611 automatically
)
in
+
+
max
if [t
2
@
@
V
V
+ t
3
is the 1 V V
in,rms
in,rms
=0), which leads to (t
V
1
V
3
2 @ L @ V
2 @ L @ V
REGUL
) is the switching period and V
(t
REGUL
V
V
1
REGUL
REGUL
+ t
2
2
@ V
@ V
2
) / T] is a constant.
max
max
on
REGUL
REGUL
REGUL
REGUL max
REGUL max
,
max
ON(HL)
@ T
is equal to 25 ms
@ T
maximum value.
ON(HL)
ON(LL)
) at high line
1
+t
2
=T) and
in
in
is
is