NCP1381 ONSEMI [ON Semiconductor], NCP1381 Datasheet - Page 24

• Manufacturer Part Number: NCP1381
• Description: Low−Standby High Performance PWM Controller
• Manufacturer: ONSEMI [ON Semiconductor]

PFC Behavior During BO Conditions
PFC controller consumption would prevent the charging of
the V
comes back and a clean startup sequence has properly ended.
Soft−start
power on sequence (P
lower the acoustical noise in the transformer. As soon as
V
from nearly zero up to the maximum clamping level (e.g.
0.8 V / R
soft−start activation.
condition to implement our soft−burst. This Soft−Skip is
cancelled whenever a fault condition appears, in order not to
degrade the transient behavior in case of load transients
when the controller is initially in skip mode.
A mix of conditions, BO, short−circuit and UVLO fault are represented on this diagram. In BO, the pulses (pulse ok signal) are started at
V
short−circuit), there is a latch−off phase but the timer is flat since there is no short−circuit.
CC
CC
During brown−out, the PFC is disabled; otherwise the
The NCP1381 features a soft−start activated during the
A shorter soft−start is also activated during the skip cycle
= 15 V and there is no latch−off phase. In short−circuit, pulses are stopped by the timer and finally, in a UVLO conditions (not a
reaches 15 V, the peak current is gradually increased
CC
capacitor. The PFC will be shutdown until BO
sense
). Every restart attempt is followed by a
ON
) and in short−circuit conditions to
BO Interruption
50.0m
V
CC
150m
Short−Circuit
Interruption
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Figure 37.
NCP1381
250m
24
0 V (Fresh P
or V
Figure 38. Soft−Start is Activated During a Startup
VCC
Comp.
Current
Pulse
Sense
V
B
CClatch
OK
CC
OK
VCC
VCC
latch
350m
OFF
ON
ON
Sequence or an OCP Condition
UVLO Interruption
)
Timer
V
in
450m
15 V
5 ms
Max I
P