Fairchild FAN480X Manuals

Fairchild FAN480X PFC+PWM Integrated Controller Application Note

This document is an application note for the Fairchild Semiconductor FAN480X series, which includes models FAN4800A, FAN4800C, FAN4801, and FAN4802. The FAN480X integrates a Power Factor Correction (PFC) unit using Switching Charge technology and a Pulse-Width Modulation (PWM) unit supporting both current and voltage mode control. It features Leading-Edge Modulation for PFC and Trailing-Edge Modulation for PWM to reduce output capacitor ripple voltage. The FAN4801 and FAN4802 variants include a programmable two-stage PFC output function to improve system efficiency at low line input voltages and light loads. The device offers various protection features such as soft-start for both PWM and PFC, over/under-voltage protection, cycle-by-cycle current limiting, and brown-out protection. It can replace the FAN4800 and ML4800 series with minor peripheral adjustments.

The guide details the design process for the PFC unit, including calculating the output capacitor voltage rating, selecting power components like inductors and switching devices, and designing the gain modulator peripheral circuit. It provides equations for determining inductor values based on current ripple, duty cycle, and switching frequency. The document also covers the selection of the current sense resistor and the design of the current-loop compensation network to ensure the current waveform follows the 120Hz input waveform while maintaining stability. This manual is written in Chinese.