Linear LT3755大电流LED控制方案

Linear公司的LT3755和LT3755-1是大电流DC/DC控制器,可作为恒流源用来驱动大电流LED. LT3755和LT3755-1通过内部的7V稳压源来驱动低边N沟功率MOSFET. LT3755和LT3755-1具有3000:1的真彩色PWM调光,输入电压可从4.5V到40V,而输出电压可高达60V,广泛应用在大功率LED驱动,工业和汽车电子领域.本文介绍了LT3755和LT3755-1的主要特性,方框图以及典型应用电路图和50W白光LED头灯驱动电路, 降压模式1.4A LED驱动电路, 20W SEPIC LED驱动电路和汽车电子用降压-升压LED驱动电路.

The LT3755 and LT3755-1 are DC/DC controllers designed to operate as a constant-current source for driving high current LEDs. They drive a low side external N-channel power MOSFET from an internal regulated 7V supply. The fixed frequency, current-mode architecture results in stable operation over a wide range of supply and output voltages.
A ground referenced voltage FB pin serves as the input for several LED protection features, and also makes it possible for the converter to operate as a constant-voltage source. A frequency adjust pin allows the user to program the frequency from 100kHz to 1MHz to optimize efficiency, performance or external component size.
The LT3755/LT3755-1 sense output current at the high side of the LED string. High side current sensing is the most flexible scheme for driving LEDs, allowing boost, buck mode or buck-boost mode configuration. The PWM input provides LED dimming ratios of up to 3000:1, and the CTRL input provides additional analog dimming capability. Both parts are available in the 16-lead (3mmX3mm) QFN package.

主要特性:
3000:1 True Color PWMTM Dimming
Wide Input Voltage Range: 4.5V to 40V
Output Voltage Up to 60V
Constant-Current and Constant-Voltage Regulation
100mV High Side Current Sense
Drives LEDs in Boost, Buck Mode, Buck-Boost Mode, SEPIC or Flyback Topology
Adjustable Frequency: 100kHz to 1MHz
Programmable Undervoltage Lockout with Hysteresis
Open LED Status Pin (LT3755)
Frequency Synchronization (LT3755-1)
PWM Disconnect Switch Driver
CTRL Pin Provides Analog Dimming
Low Shutdown Current: <1μA
Programmable Soft-Start
Thermally Enhanced 16-Lead QFN (3mm &#61655;&#61472;3mm) Package

应用:
High Power LED Applications
Industrial
Automotive



图1. LT3755方框图



图2. LT3755典型应用电路图



图3.50W白光LED头灯驱动电路图



图4. 降压模式1.4A LED驱动电路图



图5. 20W SEPIC LED驱动电路图



图6. 汽车电子用降压-升压LED驱动电路图