NCL30000(2009) Ver la hoja de datos (PDF) - ON Semiconductor
Número de pieza
componentes Descripción
Fabricante
NCL30000 Datasheet PDF : 23 Pages
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NCL30000
AC
Line
Input
EMI
FILTER
C in
RSU
ÏÏD1
R1
R ZCD
NCL30000
1 MFP
VCC 8
Q1
C1
2 COMP
DRV 7
R2
Ccomp
3 CT
GND 6
Ctim
4 CS
ZCD 5
R CS
ÏÏDout
Ra
Cv
8
VCC
RL
OUT2
Ï7
IN2+ 5
+
− IN2− 6
ÏÏ NCS1002
ÏÏ OUT1
− IN1− 2
1
+ IN1+ 3
Rb Rx
Rt
GND
4
Ry
Cc
C OUT
Rc
RLED
Figure 2. Simplified Flyback Application with Secondary side Constant Current Control
Overview
Figure 2 illustrates how the NCL30000 is configured to
implement an isolated power factor corrected flyback
switch mode power supply. On the secondary side is the
NCS1002, a constant voltage, constant current controller
which senses the average LED current and the output
voltage and provides a feedback control signal to the
primary side through an opto−coupler interface. One of the
key benefits of active power factor correction is that it makes
the load appear like a linear resistance similar to an
incandescent bulb. High power factor requires generally
sinusoidal line current and minimal phase displacement
between the line current and voltage. The NCL30000
operates in a fixed on−time variable frequency mode where
the power switch is on for the same length of time over a half
cycle of input power. The current in the primary of the
transformer starts at zero each switching cycle and is directly
proportional to the applied voltage times the on−time.
Therefore with a fixed on−time, the current will follow the
applied voltage generating a current of the same shape. Just
as in a traditional boost PFC circuit, the control bandwidth
is low so that the on−time is constant throughout a single line
cycle. The feedback signal from the secondary side is used
to modify the average on−time so the current through the
LEDs is properly regulated regardless of forward voltage
variation of the LED string.
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