Holtek公司的 HT7L4091是用于高亮led照明控制的通用PWM控制器，是逐周期电流控制、峰值电流控制法结合固定关闭时间的控制芯片。HT7L4091包含了LED开路保护、过温度保护、过低电压保护，以及加强的短路保护功能。适用于LED灯管、灯泡等通用照明；也适用于广告广告牌背光、大尺寸LCD背光等不同应用。本文介绍了HT7L4091主要特性，方框图以及多种典型应用电路。

    HT7L4091 ：Universal Step-Down PWM Control For High Brightness LED Lighting Control 

    The HT7L4091 device provides a low-cost solution for active current mode PWM controls of High Intensity LED drive systems supplied by either AC or DC line power lines. The device operates in constant off-time mode which is suitable for buck LED drivers. The low start-up and operating currents provides flexible power requirements for high efficiency or low cost applications. The switch frequency off-time can be programmed using an external resistor. The peak current mode control achieves good output current regulation without requiring loop compensations for a wide range of input voltages. 

    Included in the device is a PWM dimming input which can accept an external control signal with a duty ratio from 0 to 100%. The output current can be programmed from 0 to 250mA by applying an external control voltage on the linear dimming control input. 

    The device includes a frequency jitter function which hELps to reduce EMI power supply emissions. from damage should the LEDs be short circuited. . 

    The device requires a minimum number of external standard components and is available in an 8-pin NSOP package for small area PCB applications.

    HT7L4091主要特性：

    ●●Input supply AC voltage range: 100V~240V 

    ●●Ultra Low Power-on Start-up current < 30μA 

    ●●Integrated 25V Zener diode internally connected to VIN pin 

    ●●5V LDO output voltage with 6mA driving current for external components 

    ●●Frequency jitter function for enhanced EMI performance 

    ●●Efficiency > 85% 

    ●●Under Voltage Lockout Function - UVLO 

    ●●Current mode operation with cycle-by-cycle current limiting 

    ●●Over Temperature Protection Function 

    ●●High-current FET Drive Output 

    ●●Linear and PWM Dimming Function 

    ●●Enhanced Short Circuit Protection Function 

    HT7L4091应用： 

    ●●AC/DC and DC/DC Power control For High Power LED Lighting 

    ●●RGB back lighting LED driver 

    ●●Flat Panel Displays Back Lighting 

    ●●General Purpose Constant Current Source 

    ●●Signage and Decorative LED lighting 

    ●●Battery Chargers

图1。HT7L4091方框图

    图2。HT7L4091典型应用电路

    图3。HT7L4091没有输入大电容的应用电路

    图4。HT7L4091高效应用电路

    图5。HT7L4091 BJT电源应用电路

    应用电路材料清单：