NCP1015 ON Semiconductor, NCP1015 Datasheet - Page 13

• Manufacturer Part Number: NCP1015
• Description: Self-supplied Monolithic Switcher For Low Standby-power Offline Smps W/out Ovp
• Manufacturer: ON Semiconductor

Soft-Start
activated during the power on sequence (P
V
increased from nearly zero up to the maximum internal
clamping level (e.g. 350 mA). This situation lasts 1 ms and
further to that time period, the peak current limit is blocked
to the maximum until the supply enters regulation. The
Non-latching Shutdown
temporarily and authorize its re-start once the default has
disappeared. This option can easily be accomplished
through a single NPN bipolar transistor wired between FB
Full Latching Shutdown
when an abnormal situation is detected (over temp or
overvoltage). This feature can easily be implemented
through two external transistors wired as a discrete SCR.
CC
The NCP1015 features an internal 1 ms soft-start
In some cases, it might be desirable to shut off the part
Other applications require a full latching shutdown, e.g.
reaches V
Figure 22. A Non-latching Shutdown where Pulses are Stopped as long as the NPN is Biased
Figure 21. Soft-Start is Activated During a Start-up Sequence or an OCP Condition
CC(off)
ON/OFF
0 V (Fresh PON)
4.7 V (Overload)
V
, the peak current is gradually
Current
CC
Sense
or
ON
). As soon as
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NCP1015
13
8.5 V
soft-start is also activated during the over current burst
(OCP) sequence. Every re-start attempt is followed by a
soft-start activation. Generally speaking, the soft-start will
be activated when V
power-on sequence) or 4.5 V, the latch-off voltage
occurring during OCP. Figure 21 shows the soft-start
behavior. The time scales are purposely shifted to offer a
better zoom portion.
1.0 ms
and ground. By pulling FB below the internal skip level
(V
relaxed, the IC resumes its operation. Figure 22 shows the
application example:
When the OVP level exceeds the zener breakdown voltage,
the NPN biases the PNP and fires the equivalent SCR,
permanently bringing down the FB pin. The switching
pulses are disabled until the user un-plugs the power supply.
skip
Max Ip
), the output pulses are disabled. As soon as FB is
+
CV
CC
1
2
3
4
CC
ramps up either from zero (fresh
8
7
5
Transformer