NCL30486B
Practically, the controller extracts the duty−cycle by
If a voltage lower than V
is applied to the DIM
ADIM(EN)
measuring the current inside PDIM pin which is directly the
opto coupler collector current.
pin, the DRV pulses are disabled for controllers without the
dimming CV mode option.
If PDIM pin is left open, the controller delivers 100% of
The DIM pin is pulled up internally by a small current
source or resistor. Thus, if the pin is left open, the controller
is able to start.
I
. If the pin is pulled down for longer than 25 ms, the
out
controller is disabled.
If the PWM dimming signal is removed during dimming,
NOTE:
the controller delivers 100% of I
.
out
• Interaction between ADIM and PDIM: if ADIM and
The NCL30486B set 100% of output current when the
duty−cycle of the signal applied on PDIM is above 93%.
PDIM are both used at the same time, the resulting
dimming set point if a multiplication of V
and the
ADIM
duty−ratio of PDIM signal.
Analog Dimming
• During dimming, when the “Enable” signal is OK, the
The pin ADIM pin allows implementing analog dimming
of the LED light.
controller starts pulsing after first valley, even if a higher
valley number is selected by V
. This is to avoid too
If the power supply designer applies an analog signal
REFX
varying from V
output current will increase or decrease proportionally to the
voltage applied. For V = V , the power supply
to V
to the DIM pin, the
long startup time while dimming at low output current
value. After ZCD voltage during DRV off time is higher
DIM(EN)
DIM100
than 0.65 V, the number of valley is selected by V
.
DIM
DIM100
REFX
delivers the maximum output current (V
= 1 V).
REFX
• In order to minimize discrete output current variation
caused by valley change in deep dimming, valley
synchronization is removed when the dimming setpoint is
below 15%.
If a voltage lower than V
is applied to ADIM
ADIM(MIN)
pin, the output current is clamped to the selected dimming
clamp value (see Dimming clamp section below)
VREF
100% VREF
8% V
REF
5% V
REF
1% VREF
VADIM(EN)
VADIM100
VADIM
VADIM(MIN)
Figure 65. ADIM Pin Dimming Curves
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