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參數(shù)資料
| 型號： | LM3402 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | 0.5A Constant Current Buck Regulator for Driving High Power LEDs |
| 中文描述： | 0.5A的恒流降壓穩(wěn)壓器用于驅(qū)動高功率LED |
| 文件頁數(shù)： | 10/22頁 |
| 文件大?。?/td> | 840K |
| 代理商： | LM3402 |
Application Information
(Continued)
The LM3402/02HV regulators should be operated in continu-
ous conduction mode (CCM), where inductor current stays
positive throughout the switching cycle. During steady-state
operationin the CCM, the converter maintains a constant
switching frequency, which can be selected using the follow-
ing equation:
V
F
= forward voltage of each LED, n = number of LEDs in
series
AVERAGE LED CURRENT ACCURACY
The COT architecture regulates the valley of
V
, the AC
portion of V
. To determine the average LED current
(which is also the average inductor current) the valley induc-
tor current is calculated using the following expression:
In this equation t
represents the propagation delay of the
CS comparator, and is approximately 220 ns. The average
inductor/LED current is equal to I
L-MIN
plus one-half of the
inductor current ripple,
i
L
:
I
F
= I
L
= I
L-MIN
+
i
L
/ 2
Detailed information for the calculation of
i
L
is given in the
Design Considerations section.
MAXIMUM OUTPUT VOLTAGE
The 300 ns minimum off-time limits on the maximum duty
cycle of the converter, D
MAX
, and in turn ,the maximum
output voltage V
O(MAX)
is determined by the following equa-
tions:
The maximum number of LEDs, n
, that can be placed in
a single series string is governed by V
and the maxi-
mum forward voltage of the LEDs used, V
F(MAX)
, using the
expression:
At low switching frequency the maximum duty cycle and
output voltage are higher, allowing the LM3402/02HV to
regulate output voltages that are nearly equal to input volt-
age. The following equation relates switching frequency to
maximum output voltage.
20192105
FIGURE 1. Comparator and One-Shot
L
www.national.com
10
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM3402_07 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:0.5A Constant Current Buck Regulator for Driving High Power LEDs |
| LM3402_08 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:0.5A Constant Current Buck Regulator for Driving High Power LEDs |
| LM3402_1 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:LM3402/LM3404 Fast Dimming and True Constant LED Current Evaluation Board |
| LM3402EVAL | 功能描述:BOARD EVALUATION FOR LM3402 RoHS:是 類別:編程器，開發(fā)系統(tǒng) >> 評估板 - LED 驅(qū)動器 系列:PowerWise® 標準包裝:1 系列:PowerWise® 電流 - 輸出 / 通道:20mA 輸出及類型:1，非隔離 輸出電壓:17V 特點:可調(diào)光 輸入電壓:2.7 ~ 5.5 V 已供物品:板 已用 IC / 零件:LM3508 相關(guān)產(chǎn)品:LM3508TLX-ND - IC LED DRVR WHT BCKLGT 9USMDLM3508TLDKR-ND - IC LED DRVR WHT BCKLGT 9MICROSMDLM3508TLCT-ND - IC LED DRVR WHT BCKLGT 9MICROSMDLM3508TLTR-ND - IC LED DRVR WHT BCKLGT 9MICROSMD |
| LM3402EVAL | 制造商:Texas Instruments 功能描述:EVAL BOARD |
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