YB1520ST25 YOBON [YOBON TECHNOLOGIES,INC.], YB1520ST25 Datasheet - Page 16

• Manufacturer Part Number: YB1520ST25
• Description: High Power Step-up DC-DC Converter, White LED Driver
• Manufacturer: YOBON [YOBON TECHNOLOGIES,INC.]

LED Current and Dimming Control
The LED’s current is set by a resistor
connected at FB pin to GND using:
The maximum LED current set initially can
be reduced by pulse width modulating the
CTRL. A better approach is to adjust the
feedback voltage for dimming control.
Either a DC level signal or a filtered PWM
signal can be used to control the LED
current as illustrated in Figure 4 and Figure
5 respectively. Using the above different
scheme, the LED current can be controlled
from 20% to 80% to its maximum value.
YB1520 MRev.1.2
Figure 5. Dimming Control Using a Filtered
Figure 4. Dimming Control Using a DC Voltage
I
LED
=
200
R
LED
mV
High Power Step-up DC-DC Converter, White LED Driver
www.yobon.com.tw
Over Voltage Protection
The YB1520 has an internal over voltage
protection circuit which also acts as an
open-circuit protection. In the cases of
open circuit or the LEDs failure, the LEDs
are disconnected from the circuit, and the
feedback voltage will be zero. The YB1520
will then switch to a high duty cycle
resulting in a high output voltage, which
may cause SW pin voltage to exceed its
maximum 34V rating. The YB1520 will
shutdown automatically until input condition
changes to bring it out of the shutdown
mode.
Inductor Selection
A 47uH inductor is recommended for most
applications to drive more than 9 LEDs in
serials and 33uH inductor is recommended
for drive 30 LEDs in serials/parallel.
Although small size and high efficiency are
major concerns, the inductor should have
low core losses at 1MHz and low DCR
(copper wire resistance).
Diode Selection
To maintain high efficiency, the average
current rating of the Schottky diode should
be large than the peak inductor current, IPK.
Schottky diode with a low forward drop and
fast switching speeds are ideal for increase
efficiency in portable application. Choose a
reverse breakdown of the Schottky diode
large than the output voltage.
PWM Signal(1KHz,2Vp-p,duty 20%~80%)
YB1520
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