- 您现在的位置：买卖IC网 > PDF目录15734 > LM3445TRIACEVAL (National Semiconductor)BOARD EVAL LM3445MM PDF资料下载
参数资料
| 型号： | LM3445TRIACEVAL |
| 厂商： | National Semiconductor |
| 文件页数： | 20/40页 |
| 文件大小： | 0K |
| 描述： | BOARD EVAL LM3445MM |
| 标准包装： | 1 |
| 系列： | PowerWise® |
| 电流 - 输出 / 通道： | 770mA |
| 输出及类型： | 1，非隔离 |
| 特点： | 可调光 |
| 输入电压： | 8 ~ 12V |
| 已供物品： | 板 |
| 已用 IC / 零件： | LM3445MM |
| 相关产品： | LM3445MMX-ND - IC LED DRIVER TRIAC DIMM 10-MSOP LM3445MMDKR-ND - IC LED DRIVER TRIAC DIMM 10-MSOP LM3445MMCT-ND - IC LED DRIVER TRIAC DIMM 10-MSOP LM3445MMTR-ND - IC LED DRIVER TRIAC DIMM 10-MSOP |
第1页第2页第3页第4页第5页第6页第7页第8页第9页第10页第11页第12页第13页第14页第15页第16页第17页第18页第19页当前第20页第21页第22页第23页第24页第25页第26页第27页第28页第29页第30页第31页第32页第33页第34页第35页第36页第37页第38页第39页第40页
SNVS570L – JANUARY 2009 – REVISED MAY 2013
DETERMINING DUTY-CYCLE (D)
Duty cycle (D) approximately equals:
DESIGN GUIDE
V LED
V BUCK
=D= t ON + t OFF
t ON
= t ON x f SW
(4)
With efficiency considered:
1 u V LED = D
K V BUCK
(5)
For simplicity, choose efficiency between 75% and 85%.
CALCULATING OFF-TIME
The “Off-Time” of the LM3445 is set by the user and remains fairly constant as long as the voltage of the LED
stack remains constant. Calculating the off-time is the first step in determining the switching frequency of the
converter, which is integral in determining some external component values.
PNP transistor Q3, resistor R4, and the LED string voltage define a charging current into capacitor C11. A
constant current into a capacitor creates a linear charging characteristic.
i = C dv
dt
(6)
Resistor R4, capacitor C11 and the current through resistor R4 (i COLL ), which is approximately equal to V LED /R4,
are all fixed. Therefore, dv is fixed and linear, and dt (t OFF ) can now be calculated.
t OFF = C11 x 1.276V x
R4
V LED
(7)
Common equations for determining duty cycle and switching frequency in any buck converter:
f SW =
1
t OFF + t ON
D= t
= V LED
'? = t
Therefore:
t ON
ON + t OFF
t OFF
ON + t OFF
V
BUCK
(8)
D t -
f SW = t ON , and f SW = 1 OFF D
With efficiency of the buck converter in mind:
V LED
V BUCK = K u D
Substitute equations and rearrange:
(9)
(10)
V LED ·
K u V BUCK ?1
f SW =
§
¨ 1
?
1
t OFF
(11)
Off-time, and switching frequency can now be calculated using the equations above.
SETTING THE SWITCHING FREQUENCY
Selecting the switching frequency for nominal operating conditions is based on tradeoffs between efficiency
(better at low frequency) and solution size/cost (smaller at high frequency).
20
Product Folder Links: LM3445
Copyright ? 2009–2013, Texas Instruments Incorporated
相关PDF资料 |
PDF描述 |
|---|---|
| VE-B00-EY-F1 | CONVERTER MOD DC/DC 5V 50W |
| ISC1812RXR39K | INDUCTOR WW 390NH 10% 1812 |
| HCM12DSEH | CONN EDGECARD 24POS .156 EYELET |
| MAX6441KADGWD7+T | IC BATTERY MON DUAL SOT23-8 |
| VE-B00-EX-S | CONVERTER MOD DC/DC 5V 75W |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LM3445TRIACEVAL/NOPB | 制造商:Texas Instruments 功能描述:TRIAC Dimmable Offline LED Driver Evaluation Board |
| LM3447 | 制造商:TI 制造商全称:Texas Instruments 功能描述:Phase Dimmable, Primary Side Power Regulated PFC Flyback Controller for LED Lighting |
| LM3447-A19-120VEVM | 功能描述:LED 照明开发工具 LM3447 Eval Mod RoHS:否 制造商:Fairchild Semiconductor 产品:Evaluation Kits 用于:FL7732 核心: 电源电压:120V 系列: 封装: |
| LM3447-A19-230VEVM | 功能描述:LED 照明开发工具 LM3447 Eval Mod RoHS:否 制造商:Fairchild Semiconductor 产品:Evaluation Kits 用于:FL7732 核心: 电源电压:120V 系列: 封装: |
| LM3447MT | 制造商:TI 制造商全称:Texas Instruments 功能描述:a Phase-Dimmable, Primary-Side Regulated LED Driver |
发布紧急采购，3分钟左右您将得到回复。