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| 型号： | NSI45020AT1G |
| 厂商： | ON Semiconductor |
| 文件页数： | 6/8页 |
| 文件大小： | 156K |
| 描述： | IC LED DRIVER LINEAR SOD-123 |
| 产品培训模块： | Constant Current Regulators |
| 视频文件： | Advantages of Constant Current Regulators (CCR) in Driving LEDs |
| 特色产品： | 45V Two-Terminal LED Drivers |
| 标准包装： | 1 |
| 功能： | * |
| 检测方法： | * |
| 精确度： | * |
| 输入电压： | * |
| 电流 - 输出： | * |
| 工作温度： | * |
| 安装类型： | 表面贴装 |
| 封装/外壳： | SOD-123 |
| 供应商设备封装： | SOD-123 |
| 包装： | 标准包装 |
| 产品目录页面： | 1120 (CN2011-ZH PDF) |
| 其它名称： | NSI45020AT1GOSDKR |
NSI45020AT1G
http://onsemi.com
6
Other Currents
The adjustable CCR can be placed in parallel with any
other CCR to obtain a desired current. The adjustable CCR
provides the ability to adjust the current as LED efficiency
increases to obtain the same light output (Figure 10).
Figure 10.
Dimming using PWM
The dimming of an LED string can be easily achieved by
placing a BJT in series with the CCR (Figure 11).
Figure 11.
The method of pulsing the current through the LEDs is
known as Pulse Width Modulation (PWM) and has become
the preferred method of changing the light level. LEDs being
a silicon device, turn on and off rapidly in response to the
current through them being turned on and off. The switching
time is in the order of 100 nanoseconds, this equates to a
maximum frequency of 10 Mhz, and applications will
typically operate from a 100 Hz to 100 kHz. Below 100 Hz
the human eye will detect a flicker from the light emitted
from the LEDs. Between 500 Hz and 20 kHz the circuit may
generate audible sound. Dimming is achieved by turning the
LEDs on and off for a portion of a single cycle. This on/off
cycle is called the Duty cycle (D) and is expressed by the
amount of time the LEDs are on (Ton) divided by the total
time of an on/off cycle (Ts) (Figure 12).
Figure 12.
The current through the LEDs is constant during the period
they are turned on resulting in the light being consistent with
no shift in chromaticity (color). The brightness is in proportion
to the percentage of time that the LEDs are turned on.
Figure 13 is a typical response of Luminance vs Duty Cycle.
Figure 13. Luminous Emmitance vs. Duty Cycle
DUTY CYCLE (%)
100
90
80
70
60
50
40
0
1000
3000
2000
30
4000
6000
20
10
0
5000
Lux
Linear
Reducing EMI
Designers creating circuits switching medium to high
currents need to be concerned about Electromagnetic
Interference (EMI). The LEDs and the CCR switch
extremely fast, less than 100 nanoseconds. To help eliminate
EMI, a capacitor can be added to the circuit across R2.
(Figure 11) This will cause the slope on the rising and falling
edge on the current through the circuit to be extended. The
slope of the CCR on/off current can be controlled by the
values of R1 and C1.
The selected delay / slope will impact the frequency that
is selected to operate the dimming circuit. The longer the
delay, the lower the frequency will be. The delay time should
not be less than a 10:1 ratio of the minimum on time. The
frequency is also impacted by the resolution and dimming
steps that are required. With a delay of 1.5 microseconds on
the rise and the fall edges, the minimum on time would be
30 microseconds. If the design called for a resolution of 100
dimming steps, then a total duty cycle time (Ts) of 3
milliseconds or a frequency of 333 Hz will be required.
相关PDF资料 |
PDF描述 |
|---|---|
| NSI45020JZT1G | IC LED DRVR CONST CURRENT SOT223 |
| NSI45020T1G | IC CCR/LED DVR 45V 20MA SOD-123 |
| NSI45025AT1G | IC LED DRIVER LINEAR SOD-123 |
| NSI45025AZT1G | IC LED DRIVER LINEAR SOT-223 |
| NSI45025T1G | IC CCR/LED DVR 45V 25MA SOD-123 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| NSI45020AT1G | 制造商:ON Semiconductor 功能描述:Constant Current Regulator & LED Driver 制造商:ON Semiconductor 功能描述:IC, CCR & LED DRIVER, LINEAR, SOD-123-2 |
| NSI45020JZT1G | 功能描述:LED照明驱动器 SOT223 EUTECTIC 20MA RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N |
| NSI45020T1G | 功能描述:LED照明驱动器 SOD 123 20mA 15% CCR RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N |
| NSI45025AT1G | 功能描述:LED照明驱动器 SOD 123 25mA 10% CCR RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N |
| NSI45025AT1G | 制造商:ON Semiconductor 功能描述:Constant Current Regulator & LED Driver |
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