NCP1606 ON Semiconductor, NCP1606 Datasheet - Page 15

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

Overvoltage Protection
active PFC stages very slow systems. One consequence of
this is the risk of huge overshoots in abrupt transient phases
(startup, load steps, etc.). For reliable operation, it is
critical that some form of overvoltage protection (OVP)
effectively prevents the output voltage from rising too
high. The NCP1606 detects these excessive V
FB
Control
V
V
CC
OUT
I
The low bandwidth of the feedback network makes
switch
2.5 V
V
Figure 32. Startup Timing Diagram Showing the
EAL
Natural Soft Start of the Control Pin
Natural Soft Start
V
V
+
CC(on)
CC(off)
+
−
UVLO
Figure 33. Output Driver Stage and Pull Down Clamps
V
DD REG
OUT
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levels
V
V
DD
ddGD
15
V
CC
nV
OUTPUT DRIVER
of peak currents of +500 mA and −800 mA. This enables
the controller to efficiently drive power MOSFETs for
medium power (up to 300 W) applications. Additionally,
the driver stage is equipped with both passive and active
pull down clamps (Figure 33). The clamps are active when
V
threshold voltage of a power MOSFET.
and disables the driver until the output voltage returns to
nominal levels. This keeps the output voltage within an
acceptable range. The limit is adjustable so that the
overvoltage level can be optimally set. The level must not
be so low that it is triggered by the 100 or 120 Hz ripple of
the output voltage. But it must be low enough so as not to
require a larger voltage rating of the output capacitor.
Figure 34 depicts the operation of the OVP circuitry.
I
pullup
DD
CC
The NCP1606 includes a powerful output driver capable
is off and force the driver output to well below the
DRV IN
GND
DRV