收藏本站
Six-String White LED Driver with Active
Current Balancing for LCD Panel Applications
Table 4. Component Suppliers
Murata
Nichia
Sumida
Toshiba
Vishay
SUPPLIER
PHONE
770-436-1300
248-352-6575
847-545-6700
949-455-2000
203-268-6261
WEBSITE
www.murata.com
www.nichia.com
www.sumida.com
www.toshiba.com/taec
www.vishay.com
? V IN _ MIN ? ? V OUT ? V IN _ MIN ? ? η TYP ?
L = ? ? ? ? ? ?
components for the typical applications circuit. Table 4
lists component suppliers. External component value
choice is primarily dictated by the output voltage and the
maximum load current, as well as maximum and minimum
input voltages. Begin by selecting an inductor value.
Once L is known, choose the diode and capacitors.
Inductor Selection
The inductance, peak current rating, series resistance,
and physical size should all be considered when
selecting an inductor. These factors affect the conver-
ter’s operating mode, efficiency, maximum output load
capability, transient response time, output voltage ripple,
and cost.
The maximum output current, input voltage, output volt-
age, and switching frequency determine the inductor
value. Very high inductance minimizes the current rip-
ple, and therefore reduces the peak current, which
decreases core losses in the inductor and I 2 R losses in
the entire power path. However, large inductor values
also require more energy storage and more turns of
wire, which increases physical size and I 2 R copper
losses in the inductor. Low inductor values decrease
the physical size, but increase the current ripple and
peak current. Finding the best inductor involves the
compromises among circuit efficiency, inductor size,
and cost.
When choosing an inductor, the first step is to deter-
mine the operating mode: continuous conduction mode
(CCM) or discontinuous conduction mode (DCM). The
MAX8790 has a fixed internal slope compensation,
which requires a minimum inductor value. When CCM
mode is chosen, the ripple current and the peak cur-
rent of the inductor can be minimized. If a small-size
inductor is required, DCM mode can be chosen. In
DCM mode, the inductor value and size can be mini-
mized but the inductor ripple current and peak current
are higher than those in CCM. The controller can be
to the average DC inductor current at the full-load cur-
rent. The controller operates in DCM mode when LIR is
higher than 2.0, and it switches to CCM mode when LIR
is lower than 2.0. The best trade-off between inductor
size and converter efficiency for step-up regulators
generally has an LIR between 0.3 and 0.5. However,
depending on the AC characteristics of the inductor
core material and ratio of inductor resistance to other
power-path resistances, the best LIR can shift up or
down. If the inductor resistance is relatively high, more
ripple can be accepted to reduce the number of
required turns and increase the wire diameter. If the
inductor resistance is relatively low, increasing induc-
tance to lower the peak current can reduce losses
throughout the power path. If extremely thin high-resis-
tance inductors are used, as is common for LCD panel
applications, LIR higher than 2.0 can be chosen for
DCM operating mode.
Once a physical inductor is chosen, higher and lower
values of the inductor should be evaluated for efficiency
improvements in typical operating regions. The detail
design procedure can be described as follows:
Calculate the approximate inductor value using the typ-
ical input voltage (V IN ), the maximum output current
(I OUT(MAX) ), the expected efficiency ( η TYP ) taken from
an appropriate curve in the Typical Operating
Characteristics, and an estimate of LIR based on the
above discussion:
2
? V OUT ? ? I OUT ( MAX ) × f OSC ? ? LIR ?
The MAX8790 has a minimum inductor value limitation
for stable operation in CCM mode at low input voltage
because of the internal fixed slope compensation. The
minimum inductor value for stability is calculated by the
following equation:
stable, independent of the internal slope compensation
mode, but there is a maximum inductor value require-
ment to ensure the DCM operating mode.
The equations used here include a constant LIR, which
is the ratio of the inductor peak-to-peak ripple current
L CCM ( MIN ) =
( V OUT(MAX ) + V DIODE ? 2 × V IN(MIN) ) × R S
51 mV × f OSC ( MIN )
______________________________________________________________________________________
17
发布紧急采购，3分钟左右您将得到回复。

采购需求

(若只采购一条型号，填写一行即可)

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

*型号 *数量 厂商 批号 封装
添加更多采购

我的联系方式

*
*
*
相关PDF资料
MAX8791GTA+ IC MOSFET DRIVER 8-TQFN
MAX8811EEE+ IC DRVR DL PHASE HS 16-QSOP
MAX8821ETI+ IC LED DRVR WHITE BCKLGT 28-TQFN
MAX8822ETE+T IC LED DRVR WHITE BCKLGT 16-TQFN
MAX8830EWE+T IC LED DRVR WHITE BCKLGT 16-UCSP
MAX8831EWE+T IC LED DRIVR WHITE BCKLGT 16-WLP
MAX8834ZEWP+T IC LED DRIVR BCKLGT FLASH 20-WLP
MAX8855EVKIT+ KIT EVAL FOR MAX8855
相关代理商/技术参数
MAX8790EVKIT+ 功能描述:LED 照明开发工具 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:
MAX8791AGTA+ 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述:
MAX8791AGTA+T 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述:
MAX8791BGTA+ 功能描述:功率驱动器IC Single-Phase Synch MOSFET Driver RoHS:否 制造商:Micrel 产品:MOSFET Gate Drivers 类型:Low Cost High or Low Side MOSFET Driver 上升时间: 下降时间: 电源电压-最大:30 V 电源电压-最小:2.75 V 电源电流: 最大功率耗散: 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 封装:Tube
MAX8791BGTA+T 功能描述:功率驱动器IC Single-Phase Synch MOSFET Driver RoHS:否 制造商:Micrel 产品:MOSFET Gate Drivers 类型:Low Cost High or Low Side MOSFET Driver 上升时间: 下降时间: 电源电压-最大:30 V 电源电压-最小:2.75 V 电源电流: 最大功率耗散: 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 封装:Tube
MAX8791GTA+ 功能描述:功率驱动器IC Single-Phase Synch MOSFET Driver RoHS:否 制造商:Micrel 产品:MOSFET Gate Drivers 类型:Low Cost High or Low Side MOSFET Driver 上升时间: 下降时间: 电源电压-最大:30 V 电源电压-最小:2.75 V 电源电流: 最大功率耗散: 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 封装:Tube
MAX8791GTA+T 功能描述:功率驱动器IC Single-Phase Synch MOSFET Driver RoHS:否 制造商:Micrel 产品:MOSFET Gate Drivers 类型:Low Cost High or Low Side MOSFET Driver 上升时间: 下降时间: 电源电压-最大:30 V 电源电压-最小:2.75 V 电源电流: 最大功率耗散: 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 封装:Tube
MAX8792ETD+ 制造商:Maxim Integrated Products 功能描述:SOFT SW PWM CNTRLR 1-OUT PWM CNTRLR 600KHZ 14TDFN EP - Rail/Tube 制造商:Maxim Integrated Products 功能描述:SINGLE QUICK- PWM STEP DOWN CONTROL