ncp1608d ON Semiconductor, ncp1608d Datasheet - Page 20

• Manufacturer Part Number: ncp1608d
• Description: Critical Conduction Mode Pfc Controller Utilizing Ota
• Manufacturer: ON Semiconductor

and rapid operating point changes respectively, while FPP
protects the system against floating feedback pin
Overcurrent Protection (OCP)
current and limits the driver on time if the voltage of the CS
pin exceeds V
programmed by adjusting R
calculated using Equation 18:
probability of switching noise inadvertently triggering the
overcurrent limit. This filter blanks out the CS signal for a
duration of t
RC filter is connected between R
DRV
UVP and OVP protect the system from low bulk voltages
The dedicated CS pin of the NCP1608 senses the peak
An internal LEB filter (Figure 45) reduces the
R
3. FPP Protection: The FB pin is floating. The
sense
internal pull down resistor R
voltage below V
detects an UVP fault, the drive and error
amplifier are disabled.
C
Figure 45. OCP Circuitry with Optional
bulk
LEB
. If additional filtering is necessary, a small
ILIM
Condition 2
Condition 1
optional
V
External RC Filter
out
. The maximum peak current is
I
L(peak)
CS
UVP
. The UVP comparator
+
sense
R
R
R
LEB
V
out1
out2
sense
Condition 3
ILIM
sense
C
. The peak current is
+
COMP
FB
Control
Figure 44. Open Feedback Loop Protection
and the CS pin.
pulls down the FB
V
ILIM
FB
+
−
R
OCP
FB
(eq. 18)
http://onsemi.com
+
E/A
+
V
V
V
+
+
−
Control
V
OVP
+
−
−
UVP
+
g
REF
20
UVP
m
OVP
conditions. If FPP is not implemented and a manufacturing
error causes the FB pin to float, then V
the coupling within the system and the surrounding
environment. The coupled V
regulation limits (i.e. V
controller to deliver excessive power. The result is that V
increases until a component fails due to the voltage stress.
Shutdown Mode
standby mode of operation. To shutdown the controller, the
FB pin is forced to less than V
for shutdown (Figure 46), the designer must ensure that no
significant leakage current exists in the shutdown circuitry.
Any leakage current affects the output voltage regulation.
Shutdown
The NCP1608 enables the user to set the controller in a
(Enable EA)
Clamp
V
EAH
Figure 46. Shutting Down the PFC Stage
POK
V
out
UVP
R
R
out2
out1
< V
UVP
FB
FB
. When using the FB pin
Fault
< V
may be within the
FB
REF
1
2
3
4
is dependent on
) and cause the
NCP1608
8
7
6
5
out