ncp1234ad100r2g ON Semiconductor, ncp1234ad100r2g Datasheet - Page 19

• Manufacturer Part Number: ncp1234ad100r2g
• Description: Ncp1234 Fixed Frequency Current Mode Controller For Flyback Converters
• Manufacturer: ON Semiconductor

instance, not all the energy stored during the on time is
transferred to the output during the off time, even if the on
time duration is at its minimum (imposed by the propagation
delay of the detector added to the LEB duration). As a result,
the current sense voltage keeps on increasing above V
because the controller is blind during the LEB blanking
time. Dangerously high current can grow in the system if
nothing is done to stop the controller. That’s what the
additional comparator, that senses when the current sense
voltage on CS pin reaches V
as soon as this comparator toggles, the controller
immediately enters the protection mode (latched or
autorecovery according to the chosen option).
Under some conditions, like a winding short−circuit for
Soft-start ramp
V
CS Setpoint
V
CS(stop)
V
FB(fault)
ILIMI
ILIM
V
FB
(= 1.5 x V
over soft-start
ILIM
V
FB
Figure 33. Soft−Start
), does:
http://onsemi.com
takes
ILIM
,
19
Overpower compensation
proportional to the square of the peak current in the
discontinuous conduction mode:
the logic, the actual peak current is higher at high input
voltage than at low input voltage, leading to a significant
difference in the maximum output power delivered by the
power supply.
The power delivered by a flyback power supply is
Unfortunately, due to the inherent propagation delay of
t
SSTART
P
OUT
+
1
2
@ h @ L
p
Time
Time
Time
@ F
SW
@ I
p
2
(eq. 1)