NCP1606 ON Semiconductor, NCP1606 Datasheet - Page 10

• Manufacturer Part Number: NCP1606
• Description: Cost Effective Power Factor Controller
• Manufacturer: ON Semiconductor

a high frequency switching converter which regulates the
input current to stay in phase with the input voltage. These
circuits operate at a higher frequency and so they are
smaller, lighter in weight, and more efficient than a passive
circuit. With proper control of an active PFC stage, almost
any complex load can be made to appear in phase with the
topology for active power factor correction. With the
proper control, it produces a constant voltage while
drawing a sinusoidal current from the line. For medium
power (<300 W) applications, critical conduction mode
(also called borderline conduction mode) is the preferred
control method. Critical conduction mode (CRM) occurs at
the boundary between discontinuous conduction mode
AC Line
The boost (or step up) converter is the most popular
IN
The power switch being about zero, the input voltage
is applied across the coil. The coil current linearly
increases with a (V
Diode Bridge
V
Coil
Current
d
The power switch is ON
Rectifiers
+
−
in
/L) slope.
V
Figure 23. Schematic and Waveforms of an Ideal CRM Boost Converter
in
+
Figure 22. Active PFC Pre−Converter with the NCP1606
+
V
L
High
Frequency
Bypass
Capacitor
in
/L
I
V
coil
d
V
OUT
I
coil_pk
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NCP1606
PFC Preconverter
IN
10
The coil current flows through the diode. The coil voltage is (V
V
in
) and the coil current linearly decays with a (V
ac line, thus significantly reducing the harmonic current
content. Because of these advantages, active PFC circuits
have become the most popular way to meet harmonic
content requirements. Generally, they consist of inserting
a PFC pre−regulator between the rectifier bridge and the
bulk capacitor (Figure 22).
(DCM) and continuous conduction mode (CCM). In CRM,
the next driver on time is initiated when the boost inductor
current reaches zero. CRM operation is an ideal choice for
medium power PFC boost stages because it combines the
lower peak currents of CCM operation with the zero current
switching of DCM operation. The operation and
waveforms in a PFC boost converter are illustrated in
Figure 23.
Diode Bridge
(V
If next cycle does not start
then V
OUT
+
−
− V
d
rings towards V
The power switch is OFF
in
+
V
)/L
in
+
Bulk
Storage
Capacitor
Critical Conduction Mode:
Next current cycle starts as
soon as the core is reset.
V
in
in
L
Converter
V
d
I
OUT
coil
− V
in
)/L slope.
+
V
OUT
OUT
Load
−