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參數(shù)資料
| 型號(hào)： | KA7541D |
| 廠商： | FAIRCHILD SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Simple Ballast Controller |
| 中文描述： | 0.3 A FLUORESCENT LIGHT CONTROLLER, 56 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封裝： | SOP-8 |
| 文件頁(yè)數(shù)： | 6/14頁(yè) |
| 文件大?。?/td> | 95K |
| 代理商： | KA7541D |
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KA7541
6
Figure 2. Oscillator sawtooth & Output gate drive waveform
As a result, the switching frequency is as following
Ts = 2
×
(
Tch +
Tdis) = 15.29
μ
fsw = 1 / T
S
= 65KHz
The explicit equation calculating the size of the timing capacitor for a certain switching frequency is written below.
Soft Start
The switching frequency is linearly decreasing from the pre-heating frequency to the normal switching frequency.
In KA7541, the initial pre-heating frequency can be adjusted depending on the types of the lamps used. During the pre-heating
mode, a sixth of the soft start current (I
S
) which flows through the soft start resistor (R
S
) at pin #3 is added to the normal
timing capacitor charging current (50
μ
A). The rising and falling slope of the triangular waveform are increased due to this
added current.
Soft start current (I
S
) = 2V / R
S
Rising slope: dv / dt = i / C = (50
μ
A + I
S
/ 6) / Ct
Falling slope: dv / dt = i / C = 7
×
(50
μ
A + I
S
/ 6) / Ct
So, once the value of R
S
and Ct are known, the pre-heating frequency can be calculated straightforward by using the
following equation.
The dead time ratio during pre-heating mode is maintained to be constant as well as in normal mode.
(on duty: dead time = 7:1 )
The voltage of the soft start capacitor (C
S
) determines the soft start time (tss). When VCC voltage exceeds the start-up voltage
(Vth(st)), the soft start capacitor start to be charged by the current source (313nA). The switching frequency decreases linearly
to fsw(nor) from fsw(pre) until the soft start capacitor voltage (V
CS
) touches 2V. Therefore the soft start duration time (tss)
can be acquired by the following formula.
Vct
(Pin #2)
Voutput
(Pin #6, 7)
Charging
Period(
Tch)
Discharging
Period(
Tdis)
2.86V
1.0V
14V
0V
C
t
--------------------------------
6
–
f
sw
=
fsw pre
)
50
------------------------------------------
10
6
–
-----------
+
×
Ct
4.25
×
=
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相關(guān)代理商/技術(shù)參數(shù) |
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|---|---|
| KA7541DTF | 功能描述:開(kāi)關(guān)變換器、穩(wěn)壓器與控制器 Ballast Controller Electronic RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開(kāi)關(guān)頻率:1 MHz 工作溫度范圍: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| KA75420 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Voltage Detector |
| KA75420M | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Voltage Detector |
| KA75420MTF | 功能描述:監(jiān)控電路 Voltage Detector 4.2V RoHS:否 制造商:STMicroelectronics 監(jiān)測(cè)電壓數(shù): 監(jiān)測(cè)電壓: 欠電壓閾值: 過(guò)電壓閾值: 輸出類型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開(kāi)關(guān):No Backup 上電復(fù)位延遲（典型值）:10 s 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:UDFN-6 封裝:Reel |
| KA75420Z | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Voltage Detector |
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