基于MAX17127设计的高效白光LED驱动技术

MAX17127是Maxim公司的高效白光LED(WLED)驱动器,它的内部开关电流模式升压转换器能驱动LED阵列,多达并联6串LED,每串13个LED.每串电流匹配达到±2%,输入电压5V-26V,可调电流从10mA到30mA. 可调开关频率从250kHz 到1MHz.主要用在汽车电子系统,手持终端以及笔杆子电脑和便携式计算机显示器.本文介绍了MAX17127主要特性,功能方框图,以及典型应用电路.

The MAX17127 is a high-efficiency driver for white light-emitting diodes (LEDs). It is designed for large liquid-crystal displays (LCDs) that employ an array of LEDs as the light source. An internal switch current-mode step-up converter drives the LED array, which can be configured for up to six strings in parallel and 13 LEDs per string. Each string is terminated with ballast that achieves ±2% current-regulation accuracy, ensuring even LED brightness. The MAX17127 has a wide input-voltage range from 5V to 26V, and provides an adjustable 10mA to 30mA full-scale LED current.

The MAX17127 can implement brightness control through the PWM signal input, and LED current is directly controlled by the external dimming signal’s frequency and duty cycle.

The MAX17127 has multiple features to protect the controller from fault conditions. Once an open/short string is detected, the fault string is disabled while other strings can still operate normally. The controller features cycle-by-cycle current limit to provide constant operation and soft-start capability. If the MAX17127 is in current-limit condition, the step-up converter is latched off after an internal timer expires. A thermal-shutdown circuit provides another level of protection. When thermal shutdown happens, the MAX17127 is latched off.

The MAX17127’s step-up controller features an internal 0.12Ω (typ), 48V (max) power MOSFET with local current-sense amplifier for accurate cycle-by-cycle current limit. This architecture greatly simplifies the external circuitry and saves PCB space. Low-feedback voltage at each LED string helps reduce power loss and improve efficiency. The MAX17127 features resistor-adjustable switching frequency from 250kHz to 1MHz, which enables a wide variety of applications that can trade off component size for operating frequency.

The MAX17127 is available in a thermally enhanced, lead-free, 20-pin, 4mm x 4mm thin QFN package.

MAX17127主要特性:

5V to 26V Input Supply Voltage

Up to Six Parallel Strings Multiple Series-Connected LEDs

250kHz to 1MHz Adjustable Switching Frequency

0.12Ω Internal HV Power MOSFET (48V max)

Low String Feedback Voltage: 480mV at 20mA LED Current

Full-Scale LED Current Adjustable from 10mA to 30mA

±2% Current-Regulation Accuracy Between Strings

400ns Minimum String On-Time

100Hz to 25kHz PWM Input Range

Open and Short LED Protection

Output Overvoltage Protection

Thermal Shutdown

Small 20-Pin, 4mm x 4mm Thin QFN Package

MAX17127应用:

Automotive Systems

Handy Terminals

Notebook, Subnotebook, and Tablet Computer Displays


图1.MAX17127功能方框图

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图2.MAX17127简化应用电路(直接PWM模式)

图3.MAX17127典型应用电路