YB1518
Step-up DC-DC Converter White LED Driver
5 respectively. Using the above different
scheme, the LED current can be controlled
from 0% to 100% to its maximum value.
Duty
0%
20%
30%
40%
50%
60%
70%
80%
100%
Iout ( mA)
20
17.4
15
12.4
10
8
6.4
4.07
0
PWM : 2V ; 1KHz ;
Vin=3.6V
V
DC(V)
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
V
FB
0
2.2
9.2
19.6
31.1
43.4
63
74
86.4
96.9
102
Iout(mA)
0
0.43
1.8
3.6
6
8.5
12.3
14.5
16.9
19
20
Figure 5. Dimming Control Using
a Filtered PWM Signal
Over Voltage Protection
The YB1518 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 YB1518
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 YB1518 will
shutdown automatically until input condition
changes to bring it out of the shutdown
mode.
Inductor Selection
A 22uH inductor is recommended for most
applications to drive more than 5 LEDs.
Figure 4. Dimming Control Using
a DC Voltage
YB1518 MRev.1.2
www.yobon.com.tw
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YOBON [ YOBON TECHNOLOGIES,INC. ]
