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參數(shù)資料
| 型號(hào)： | MAX8722EEG |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Low-Cost CCFL Backlight Controller |
| 中文描述： | FLUORESCENT LIGHT CONTROLLER, PDSO24 |
| 封裝： | 0.150 INCH, 0.250 INCH PITCH, MO-137AE, QSOP-24 |
| 文件頁數(shù)： | 14/20頁 |
| 文件大小： | 331K |
| 代理商： | MAX8722EEG |
M
Figure 5 shows the frequency response of the resonant
tank’s voltage gain under different load conditions.
The primary series capacitor is 1μF, the secondary par-
allel capacitor is 15pF, the transformer turns ratio is
1:93, and the secondary leakage inductance is 260mH.
Notice that there are two peaks, f
S
and f
P
, in the fre-
quency response. The first peak, f
S
, is the series reso-
nant peak determined by the secondary leakage
inductance (L) and the series capacitor reflected to the
secondary (C’
S
):
The second peak, f
P
, is the parallel resonant peak
determined by the secondary leakage inductance (L),
the parallel capacitor (C
P
), and the series capacitor
reflected to the secondary (C’
S
):
The inverter is designed to operate between these two
resonant peaks. When the lamp is off, the operating
point of the resonant tank is close to the parallel resonant
peak due to the lamp’s infinite impedance. The circuit
displays the characteristics of a parallel-loaded resonant
converter. While in parallel-loaded resonant operation,
the inverter behaves like a voltage source to generate
the necessary striking voltage. Theoretically, the output
voltage of the resonant converter will increase until the
lamp is ionized or until it reaches the IC’s secondary volt-
age limit, without regard to the transformer turns ratio or
the input voltage level. Once the lamp is ionized, the
equivalent load resistance decreases rapidly and the
operating point moves toward the series resonant peak.
While in series resonant operation, the inverter behaves
like a current source.
Lamp-Current Regulation
The MAX8722 uses a lamp-current control loop to regu-
late the current delivered to the CCFL. The heart of the
control loop is a transconductance error amplifier. The
AC lamp current is sensed with a resistor connected in
series with the low-voltage terminal of the lamp. The
voltage across this resistor is fed to the IFB input and is
internally full-wave rectified. The transconductance
error amplifier compares the rectified IFB voltage with a
790mV (typ) internal threshold to generate an error cur-
rent. The error current charges and discharges a
capacitor connected between COMP and ground to
create an error voltage (V
COMP
). V
COMP
is then com-
pared with an internal ramp signal to set the high-side
MOSFET switch on-time (t
ON
).
f
P
=
1
2
π
L
C'
S
C
P
C'
S
+
C
P
f
LC
S
S
'
=
1
2
π
Low-Cost CCFL Bac klight Controller
14
______________________________________________________________________________________
AC
SOURCE
CCFL
C
P
L
C
S
1:N
(a)
AC
SOURCE
R
L
C
P
L
C'
S
=
(b)
C
S
N
2
Figure 4. Equivalent Resonant Tank Circuit
FREQUENCY (kHz)
V
80
60
40
20
1
2
3
4
0
0
100
R
L
INCREASING
f
P
f
S
Figure 5. Frequency Response of the Resonant Tank
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX8722EEG+ | 功能描述:顯示驅(qū)動(dòng)器和控制器 CCFL Backlight Controller RoHS:否 制造商:Panasonic Electronic Components 工作電源電壓:2.7 V to 5.5 V 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-44 封裝:Reel |
| MAX8722EEG+T | 功能描述:顯示驅(qū)動(dòng)器和控制器 CCFL Backlight Controller RoHS:否 制造商:Panasonic Electronic Components 工作電源電壓:2.7 V to 5.5 V 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-44 封裝:Reel |
| MAX8722EEG-T | 功能描述:顯示驅(qū)動(dòng)器和控制器 RoHS:否 制造商:Panasonic Electronic Components 工作電源電壓:2.7 V to 5.5 V 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-44 封裝:Reel |
| MAX8722EVKIT | 功能描述:顯示開發(fā)工具 Low-Cost CCFL Backlight Controller RoHS:否 制造商:4D Systems 產(chǎn)品:4Display Shields 工具用于評(píng)估:?OLED-160-G1, ?OLED-160-G2 接口類型:Serial 工作電源電壓:5 V |
| MAX8723ETE+ | 功能描述:顯示驅(qū)動(dòng)器和控制器 Int-Switch Step-Down Regulator for LCDs RoHS:否 制造商:Panasonic Electronic Components 工作電源電壓:2.7 V to 5.5 V 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-44 封裝:Reel |
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