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2008 Fairchild Semiconductor Corporation www.fairchildsemi.com Rev. 1.0.2 ? 6/21/13 AN-8027 FAN480X PFC+PWM集成控制器 FAN4800AU / FAN4800AS / FAN4800CU / FAN4800CS / FAN4801S / FAN4802S 1. 简介 这篇应用指南用於帮助使用者使用FAN480X设计 高效率的电源供应器,FAN480X由采用平均电流控制 模式的PFC (Power Factor Correction)和PWM (Pulse- Width Modulation) 两种控制器组成,其中PFC 采用 Switching Charge 技术的乘法器可以获得较高的功因 PF (Power Factor)与较低的总谐波失真THD (Total Harmonic Distortion),PWM可采用电流模式控制或是 电压模式控制.PFC调变控制为前缘调变(Leading- Edge Modulation)控制,而PWM调变控制采用后缘调变 控制(Trailing-Edge Modulation),因为采用不同触发的 调变控制可以降低PFC 输出电容上的涟波电压.FAN4801S/2S增加可规划的两段式PFC输出功能,可 使低交流输入电压且轻载时的系统效率能提升. FAN480X可取代FAN4800与ML4800,只需在周边 零件上作些许的调整.FAN480X系列的功能比较表请 见附录一的表格十二. FAN480X具有多种保护功能,其中包含PWM与PFC 的软式启动(Soft-Start) 、 PFC 过压/欠压(Over- Voltage Protection / Under-Voltage Protection)保护、 逐周期电流限制(Cycle-by-Cycle Current Limit),低交 流输入电压(Brown-out)等保护,确保电源与后级设备不 受损坏.使用者可以利用本篇所述的方程式选择所需的 关键元件.图一为FAN480X的应用线路图,其中输出 瓦数为300 W (10 W由待机电源(Standby)所提供),交 流输入电压围是90 ~