Holtek HT7939大电流白光LED驱动方案

Holtek 公司的HT7939是大电流和高性能白光LED驱动器,输入电压从2.6V到5.5V,固定开关频率1.2MHz,内置功率MOSFET,5V输入时可驱动39个白光LED, DD电流通过外部电阻设定,待机电流产 0.1uA,效率高达90%,集成了过压保护,超温保护和过流保护.主要用在显示器背光照明,DVD播放器,数码相框,手持计算机,LED照明和自动化.本文介绍HT7939主要特性, 方框图和多种应用电路,包括驱动39个WLED应用电路图, 采用PWM逻辑信号和DC电压的调光控制应用电路图以及驱动3个高亮LED应用电路图等.

HT7939: High Current and Performance White LED Driver

The HT7939 is a high efficiency boost converter for driving White LEDs using current mode operation. The device is designed to drive up to 39 White LEDs from a 5V power supply. The White LED current is setup using an external current setting resistor, which has a low feedbackvoltage of 0.2V to minimise power losses in the resistor which improves efficiency. The Over-voltage function prevents damage to the IC by turning off the converter when the LED load is open circuit.

The device includes over current protection, over temperature protection and under voltage protection preventingdamage to the device when the output is overloaded.

HT7939主要特性:

_ Input range from 2.6V~5.5V

_ Built-in Power MOSFET

_ Can drive up to 39 White LEDs with a 5V input

_ Low standby current: 0.1uA (typ.) with VEN low

_ Integrated Over-voltage, Over-temperature and Over-current protection circuits

_ Under voltage lock-out protection

_ 1.2MHz fixed switching frequency

_ High efficiency - up to 90%

_ 6-pin SOT23-6 package

HT7939应用:

_ Display Backlighting

_ Automatic

_ DVD player

_ Digital photo frame

_ Handheld computer

_ LED lighting

图1.HT7939方框图


图2.HT7939驱动39个WLED应用电路图

图3.HT7939采用PWM逻辑信号的调光控制应用电路图

图4.HT7939采用DC电压的调光控制应用电路图

图5.HT7939采用滤波的PWM信号的调光控制应用电路图

图6.HT7939驱动3个高亮LED应用电路图