参数资料
| 型号： | MAX8785AETI+T |
| 厂商： | Maxim Integrated |
| 文件页数： | 12/19页 |
| 文件大小： | 0K |
| 描述： | IC CCFL CTRL 28-TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 类型： | CCFL 控制器 |
| 电流 - 电源： | 1.5mA |
| 电源电压： | 4.5 V ~ 28 V |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 28-WFQFN 裸露焊盘 |
| 供应商设备封装： | 28-TQFN-EP（5x5） |
| 包装： | 带卷 (TR) |
Full-Bridge Controller for
Piezoelectric Transformers
1
L
C
R
1:n
3
PRIMARY
SECONDARY
V IN
FORCE
V OUT
V IN
C INPUT
C OUT
R LOAD
V IN
V OUT
CCFL
2
4
Figure 4. Electrical Model of Piezoelectric Transformer
t
VOLTAGE
RATIO
CCFL MAXIMUM PERMISSIBLE
Figure 3. Typical Multilayer PZT in Longitudinal Mode
APPLIED VOLTAGE
OPERATING
The MAX8785A can achieve 10:1 dimming range with
the DPWM method. CCFL brightness can be adjusted
using analog or digital dimming control. Analog voltage
OPERATING
POINT B
CCFL MINIMUM
STARTING VOLTAGE
on CNTL controls duty ratio of DPWM and an external
resistor on LF (R LF ) controls the frequency of DPWM.
The digital signal on LSYNC controls the duty ratio and
frequency of DPWM.
The MAX8785A guarantees lamp striking by sweeping
the switching frequency from high to low until the lamp
POINT D
OUTPUT VOLTAGE
CURVE WITH NO LOAD
OPERATING
POINT A
strikes. The maximum switching frequency can be
adjusted with an external resistor. The MAX8785A volt-
age-controlled oscillator changes the switching fre-
quency to regulate the lamp current.
OPERATING POINT C
OUTPUT VOLTAGE
CURVE IN OPERATION
FREQUENCY
The MAX8785A provides protection against lamp arc,
open lamp, secondary short circuit, and primary over-
OPERATING
FREQUENCY
RESONANCE FREQUENCY
WITH NO LOAD
current. The MAX8785A includes an adjustable fault delay
timer and an open-drain fault indicator. The MAX8785A
has primary current limiting by using lossless current
sensing to prevent overstressing the power MOSFETs.
Piezoelectric Transformer
(PZT) Background
Piezoelectric transformers transfer energy from primary
to secondary through use of mechanical force. Figure 3
shows that when electric potential is applied to the pri-
mary of the piezoelectric material, the electrical energy is
converted into mechanical vibrations (reverse piezoelec-
tric effect). These mechanical vibrations are coupled into
the secondary piezoelectric material, and then the piezo-
electric material converts the mechanical vibrations to
electrical energy (direct piezoelectric effect).
A piezoelectric transformer has a voltage gain from pri-
mary to secondary. The voltage gain of the transformer
changes with the excitation frequency of the primary. A
simplified electrical model that predicts the gain of a
Figure 5. Voltage Ratio vs. Frequency for Resonant Tank
piezoelectric transformer is shown in Figure 4. Terminals
1 and 2 are the primary and terminals 3 and 4 are the
secondary of the transformer. Many PZT manufacturers
provide component values for the model based on mea-
surements taken at various frequencies and output loads.
Figure 5 shows the variation of voltage gain with fre-
quency. During startup, the lamp is not ionized, and
therefore, has a no-load condition, so the piezoelectric
transformer operates on a high-gain, high-impedance
load line. Since the exact strike voltage and operating
frequency are not known, the MAX8785A applies a rel-
atively low voltage to the lamp by operating at the maxi-
mum-programmed operational frequency. This is
shown as Point A. As the operating frequency is
decreased, the piezoelectric transformer gain moves
up the no-load curve until the CCFL strike voltage is
reached. This is shown as operating Point B. At Point B,
12
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX8785AEVKIT# | 功能描述:LED 照明开发工具 MAX8785A Eval Kit 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: |
| MAX8785ETI+ | 功能描述:显示驱动器和控制器 Full-Bridge CCFL Controller RoHS:否 制造商:Panasonic Electronic Components 工作电源电压:2.7 V to 5.5 V 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:QFN-44 封装:Reel |
| MAX8785ETI+T | 功能描述:显示驱动器和控制器 Full-Bridge CCFL Controller RoHS:否 制造商:Panasonic Electronic Components 工作电源电压:2.7 V to 5.5 V 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:QFN-44 封装:Reel |
| MAX8785EVKIT | 功能描述:显示开发工具 MAX8785 Eval Kit RoHS:否 制造商:4D Systems 产品:4Display Shields 工具用于评估:?OLED-160-G1, ?OLED-160-G2 接口类型:Serial 工作电源电压:5 V |
| MAX8786GTL+ | 制造商:Maxim Integrated Products 功能描述:CONVERTOR - Bulk 制造商:Rochester Electronics LLC 功能描述: |
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