ncp1234ad100r2g ON Semiconductor, ncp1234ad100r2g Datasheet - Page 14

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

High−Voltage Current Source with Built−in Brown−out
Detection
The NCP1234 HV pin can be connected either to the
rectified bulk voltage, or to the ac line through a rectifier.
Start−up
on the HV pin is higher than V
V
V
controller actually starts the next time V
between V
current source on and off, it can only be used in light load
CC
CC(min)
At start−up, the current source turns on when the voltage
Even though the DSS is able to maintain the V
reaches V
, until V
CC(on)
CC(on)
CC
and V
, then turns on again when V
is supplied by an internal source. The
CC(min)
VCC
Figure 27. HV Start−up Current Source Functional Schematic
HV
HV(min)
by turning the HV start−up
, and turns off when
CC
reaches V
I
start
DETAILED DESCRIPTION
CC
CC
reaches
voltage
http://onsemi.com
CC(on)
Control
+
+
+
+
V
V
V
V
.
CC(on)
CC(min)
CC(off )
CC(reset)
+
+
+
+
−
−
−
−
14
However, the overpower compensation will work correctly
only if the HV pin is connected to the bulk voltage.
condition, otherwise the power dissipation on the die would
be too much. As a result, an auxiliary voltage source is
needed to supply V
switching pulses are delivered, e.g. in latch condition, or to
prevent the controller from stopping during load transients
when the V
t
The DSS is useful to keep the controller alive when no
blanking
UVLO(blank)
IC Start
CC
Reset
R
S
might drop.
Q
CC
during normal operation.
UVLO
TSD