原标题：Fairchild FL7701带PFC的智能LED驱动方案

　　Fairchild 公司的FL7701是带PFC功能的智能LED灯驱动器，内置高压自偏压电路，数字实现有源PFC功能，带自动重起模式的AOCP功能，内置超温保护功能，典型的工作电流0.85mA，可编程振荡器频率和LED电流，主要用在LED装饰照明和低功率LED照明。本文介绍了FL7701主要特性，方框图，有和没有电解电容的应用电路图以及2.52W参考设计主要特性和指标，电路图和PCB布局图。

　　FL7701：Smart LED Lamp Driver IC with PFC function

　　The FL7701 LED lamp driver is a simple IC with PFC function. The special “adopted digital” technique of the IC can automatically detect input voltage condition and send an internal reference signal for achieving high power factor. When AC input is applied to the IC, PFC function is automatically enabled. Otherwise, when DC input is applied to the IC, PFC function is automatically disabled. The FL7701 does not need a bulk capacitor (electrolytic capacitor) for supply rail stability, which can significantly affect to LED lamp system.

　　FL7701主要特性：

　　 Digitally Implemented Active PFC Function (No Additional Circuit Necessary for High PF)

　　 Built-in HV Supplying Circuit: Self Biasing

　　 AOCP Function with Auto-Restart Mode

　　 Built-in Over-Temperature Protection Function

　　 Cycle-by-Cycle Current Limit

　　 Current-Sense Pin Open Protection

　　 Low Operating Current: 0.85mA (Typical)

　　 Under-Voltage Lockout with 5V Hysteresis

　　 Programmable Oscillation Frequency

　　 Programmable LED Current

　　 Analog Dimming Function

　　 Soft-Start Function

　　 Precise Internal Reference: ±3%

　　FL7701应用：

　　 LED Lamp for Decorative Lighting

　　 LED Lamp for Low-Power Lighting

　　图1。FL7701方框图

　　图2。FL7701没有电解电容的应用电路图

　　图3。FL7701有电解电容的应用电路图

　　FL7701参考设计指标：

　　FL7701参考设计主要特性：

　　Digital implemented active PFC function

　　Built in HV supplying circuit: Self biasing

　　AOCP function with auto restart mode

　　Cycle-by-cycle current limit

　　Current sense pin open protection

　　Low operating current: 0.85mA (typ.)

　　Programmable Oscillation Frequency

　　Programmable LED Current

　　Analog Dimming Function

　　图4。FL7701参考设计电路图

　　图5。FL7701参考设计外形图