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參數(shù)資料
| 型號： | R1218K021A |
| 廠商： | Ricoh Co., Ltd. |
| 英文描述： | Step-up DC/DC converter for White LED Backlight |
| 中文描述： | 升壓直流/直流轉(zhuǎn)換器的白光LED背光 |
| 文件頁數(shù)： | 7/21頁 |
| 文件大?。?/td> | 679K |
| 代理商： | R1218K021A |
R1218x
7
(2) Dimming control by DC voltage
LED dimming control is also possible by using the DC voltage to V
FB
pin. LED current is adjustable by DC
voltage and resisters, R1 and R2 in the following figure.
I
LED
=
(DC
0.2) / R2
0.2 / R1
DC
V
FB
R1
R2
Dimming control by DC voltage
(3) Dimming control by feedback voltage and filtered PWM signal
LED dimming control is also possible by using the feedback voltage and filtered PWM signal.
LED current is adjustable according to the "H" level (V
H
) and "L" level(V
L
) of PWM signal and resisters,
V
H
V
L
V
FB
R3
R2
R1
R4
C3
Dimming controle by filtered PWM signal
R1, R2, R3, and R4 in the figure5. Duty
=
0% to 100% PWM signal duty cycle can be used up to the
maximum LED current and minimum LED current as in the next formulas.
I
LEDMIN
=
(0.2
R2
×
(V
H
0.2) / (R3
+
R4)) / R1
I
LEDMAX
=
(0.2
R2
×
(V
L
0.2) / (R3
+
R4)) / R1
For example, supposed that the PWM signal level is set as 2.5V/0V, to adjust the LED current range from 0mA
to 20mA by the duty cycle, our recommendation external components values are, R1=10
, R2=5.1k
,
R3=51k
, R4=5.1k
or around.
C3 should be set large enough to regard the PWM signal as adjustable DC voltage by the filter. In this method,
higher frequency control than the frequency against the CE pin can be used for dimming control.
For example, if the frequency is 40kHz, 0.1
μ
F or more capacitor is our recommendation value as C3.
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PDF描述 |
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| R1218K031A | Step-up DC/DC converter for White LED Backlight |
| R1218K041A | Step-up DC/DC converter for White LED Backlight |
| R1218K052A | Step-up DC/DC converter for White LED Backlight |
| R1218K062A | Step-up DC/DC converter for White LED Backlight |
| R1218N021A | Step-up DC/DC converter for White LED Backlight |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| R1218K031A | 制造商:RICOH 制造商全稱:RICOH electronics devices division 功能描述:Step-up DC/DC converter for White LED Backlight |
| R1218K041A | 制造商:RICOH 制造商全稱:RICOH electronics devices division 功能描述:Step-up DC/DC converter for White LED Backlight |
| R1218K052A | 制造商:RICOH 制造商全稱:RICOH electronics devices division 功能描述:Step-up DC/DC converter for White LED Backlight |
| R1218K062A | 制造商:RICOH 制造商全稱:RICOH electronics devices division 功能描述:Step-up DC/DC converter for White LED Backlight |
| R1218N021A | 制造商:RICOH 制造商全稱:RICOH electronics devices division 功能描述:Step-up DC/DC converter for White LED Backlight |
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