NCP1237 ONSEMI [ON Semiconductor], NCP1237 Datasheet - Page 20

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

Classical Overcurrent Protection
supply, the feedback loop asks for more power than the
controller can deliver, and the CS setpoint reaches V
When this event occurs, an internal t
once the timer times out, DRV pulses are stopped and the
t
if not, the system starts a new burst cycle (see Figure 18).
autorec
When an overcurrent occurs on the output of the power
In autorecovery mode, the controller tries to restart after
. If the fault has gone, the supply resumes operation;
FB
CS
blanking
t
/ 5
LEB
OVERCURRENT PROTECTION WITH FAULT TIMER
+
Figure 17. Timer−Based Overcurrent Protection
V
fault
ILIM
+
+
−
−
PWM
timer is started:
S
R
Q
http://onsemi.com
ILIM
.
DC
DRV
Brown−out
timer
20
Fault Flag
t
MAX
fault
controller is either latched off (latched protection,
Version A), or it enters an autorecovery mode (Version B).
The timer is reset when the CS setpoint goes back below
V
if the driver signal is reset by the max duty ratio.
Reset
ILIM
before the timer elapses. The fault timer is also started
Protection
Mode
release
timer
t autorec
Autorecovery
mode only
protection
Reset DRV