TS1937 데이터 시트보기 (PDF) - TSC Corporation
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TS1937 Datasheet PDF : 8 Pages
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TS1937
Boost (Step-up) WLED Driver
Application Information (Continue)
Reference Design Information
VIN Range
(V)
5
9
12
15
VOUT Max.
(V)
36
36
36
36
L (uH)
22
33
47
68
LED
(Series)
6pcs
11pcs
12pcs
12pcs
Current
(mA)
20
20
20
20
Resistor
(Ω)
4.75
4.75
4.75
4.75
Efficiency
(%)
83.5
84.2
84.3
84.6
LED Dimming Control
There are some different types of dimming control circuits:
1. Using a PWM Signal to SHDN Pin
With the PWM signal applied to the SHDN pin, the TS1937 is turned on or off by the PWM signal. The LEDs operate at
either zero or full current. The average LED current increases proportionally with the duty cycle of the PWM signal. A
0% duty cycle will turn off the TS1937 and corresponds to zero LED current. A 100% duty cycle corresponds to full
current. The typical frequency range of the PWM signal is 1kHz to 10kHz.
The magnitude of the PWM signal should be higher than the minimum SHDN voltage high.
For some applications, the preferred method of brightness control is a variable DC voltage to adjust the LED current.
The dimming control using a DC voltage is shown in Figure 4. As the DC voltage increases, the voltage drop on R2
increases and the voltage drop on R1 decreases. Thus, the LED current decreases. The selection of R2 and R3 will
make the current from the variable DC source much smaller than the LED current and much larger than the FB pin bias
current. For VDC range from 0V to 2V, the selection of resistors in Figure 4 gives dimming control of LED current from
0mA to 20mA.
Dimming Control using a DC Voltage
VDC(V)
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
VFB
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
5/8
Version: C07
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