Holtek公司的 HT7L4091是用于高亮LED照明控制的通用PWM控制器，是逐周期電流控制、峰值電流控制法結合固定關閉時間的控制芯片。HT7L4091包含了LED開路保護、過溫度保護、過低電壓保護，以及加強的短路保護功能。適用于LED燈管、燈泡等通用照明；也適用于廣告廣告牌背光、大尺寸LCD背光等不同應用。本文介紹了HT7L4091主要特性，方框圖以及多種典型應用電路。
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應用：
●●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
圖1。HT7L4091方框圖
圖2。HT7L4091典型應用電路
圖3。HT7L4091沒有輸入大電容的應用電路
圖4。HT7L4091高效應用電路
圖5。HT7L4091 BJT電源應用電路
應用電路材料清單：
詳情請見：
http://www.holtek.com.tw/PDF/consumer/HT7L4091v100.pdf
