NCP1028 ON Semiconductor, NCP1028 Datasheet - Page 17

• Manufacturer Part Number: NCP1028
• Description: High?voltage Switcher For Medium Power Offline Smps
• Manufacturer: ON Semiconductor

36 mW in nominal high-line operation. Figure 29b
simulation result confirms our calculations.
condition. Please note that output pulses only reappear
wire a filtering capacitor between BO and GND (close to
the circuit) to avoid adversely triggering the internal latch
(unless this is a wanted feature) when the pulse train
appears.
Latchoff Protection
fully turned-off and stay latched. This can happen in the
The bridge power dissipation is 330
Figure 30 describes signal variations during a brown-out
Depending on input surge tests, it might be necessary to
There are some situations where the converter shall be
Figure 30. Signal Evolution During a Brown-Out Condition
2
/3.018 Meg =
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NCP1028
17
when V
sequence. As in fault mode conditions, the startup source
is activated on and off and self-supplies the controller in a
Dynamic Self-Supply (DSS) mode.
presence of a secondary overvoltage (the feedback loop is
drifting) or when an overtemperature is detected.
Secondary monitoring is usually implemented when the
coupling between auxiliary and power windings does not
lead to a precise primary detection. Due to the addition of
a comparator on the BO pin, a simple external circuit can
lift up this pin above VLATCH and permanently disable
pulses. The V
typically to reset the controller.
CC
reaches V
CC
needs to be cycled down below 3.5 V
CC(ON)
, ensuring a clean startup