Datasheet

NCL30000
http://onsemi.com
15
MFP
COMP
EA
+
gm
UVP
+
OVP
+
OVP Fault
(Enable EA)
UVP Fault
C
COMP
V
Control
V
REF
Bias
R
1
R
2
R
FB
+
−
+
−
+
−
V
OVP
V
UVP
POWER GOOD
Shutdown
Figure 29. Multi−Function Pin Operation
The positive input of the transconductance amplifier is
connected to a 2.5 V (nominal) reference. This allows the
controller to be used in non-isolated applications where the
MFP could be configured in a more classical feedback input
configuration.
V
CC
Management
The NCL30000 incorporates a supervisory circuitry to
manage the startup and shutdown of the circuit. By
managing the startup and keeping the initial startup current
at less than 35 mA, a startup resistor connected between the
rectified ac line and V
CC
charges the V
CC
capacitor to
V
CC(on)
. Turn on of the device occurs when the startup
voltage has exceeded 12 V (nominal) when the internal
reference and switching logic are enabled. A UVLO
comparator with a hysteresis of 2.5 V nominal gives ample
time for the device to start switching and allow the bias from
the auxiliary winding to supply V
CC.
Example Design
A practical design case will be used to illustrate the overall
power supply functional blocks and the overall design
methodology. The power supply specification in this
example is listed below and covers an extended universal
input range which includes the normal 90−265 Vac for
global power supplies with an extended upper range to
support 277 Vac commercial lighting in the United States.
 Input voltage: 90 to 305 Vac
 Power factor: > 0.9
 Output current: 350 mA Typical
 LED load voltage: 12 to 50 Vdc
 Full Load Efficiency: > 85%