NCP1237 ONSEMI [ON Semiconductor], NCP1237 Datasheet - Page 23

• Manufacturer Part Number: NCP1237
• Description: Fixed Frequency Current Mode Controller for Flyback Converters
• Manufacturer: ONSEMI [ON Semiconductor]

Dual−Level Overcurrent Protection
necessary that the controller maintains regulation while it
has detected a first level of overload. This is to authorize a
transient peak power higher than the maximum continuous
output power.
For some applications (e.g. printer adapters), it is
FB
CS
blanking
K
t
LEB
FB
Figure 20. Dual−Level Timer−Based Overcurrent Protection
+
V
CS(tran)
+
+
PWM
−
−
Fault Flag
S
R
Q
http://onsemi.com
Brown−out
t
t
23
tran
fault
threshold is V
which starts the charging of another timer, with a duration
t
its maximum duration, the controller enters protection mode
(latched or autorecovery depending on the option).
tran
Reset
timer
This is implemented by adding another comparator whose
longer than t
Protection
Mode
release
CS(tran)
fault
, a CS voltage level lower than V
(168 ms typical). If the timer reaches
timer
t
autorec
Autorecovery
mode only
protection
Reset DRV
ILIM
,