NCL30081_15 Datasheet, PDF (19/30 Pages) ON Semiconductor – Dimmable Quasi-Resonant Primary Side Current-Mode Controller for LED Lighting

NCL30081
CS
Rsense
LEB1
+
Vcontrol −
+
−
V_ILIMIT
LEB2
+
−
V_CS(stop)
PWMreset
Ipkmax
S
Q
DRV
Vdd
Q
latch
R
Vcc
management
aux
VCC
UVLO
VCCstop
8_HICC
grand
reset
WOD_SCP
OVP
8_HICC
STOP
OVP
S
Q
OFF
WOD_SCP
Q
latch
S
Q
Q
R
R
grand
reset
from Fault Management Block
Figure 45. Winding Short Circuit Protection, Max. Peak Current Limit Circuits
Step Dimming
The step dimming function decreases the output current
from 100% to 5% of its nominal value in discrete steps.
There are 5 steps in total. Table 4 shows the different steps
value and the corresponding output current set−point. Each
time a brown−out is detected, the output current is decreased
by decreasing the reference voltage V_REF setting the output
current value.
When the 5% dimming step is reached, if a brown−out
event occurs, the controller restarts at 100% of the output
current.
Table 4. DIMMING STEPS
Dimming Step
ON
I_out
100%
1
70%
2
40%
3
25%
4
10%
5
5%
Perceived Light
100%
84%
63%
50%
32%
17%
Note:
The power supply designer must ensure that V_CC stays
high enough when the light is turned−off to let the controller
memorize the dimming step state.
The power supply designer should use a split V_CC circuit
for step dimming with a capacitor allowing providing
enough V_CC for 1 s (47 mF to 100 mF capacitor).
The step dimming state is memorized by the controller
until V_CC crosses V_CC(reset).
VCC
4.7 mF
47 − 100 mF
Figure 46. Split VCC Supply
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