原标题：Fairchild FAN9612双BCM BFC控制器方案

　　Fairchild 公司的FAN9612是隔行扫描的双临界工作模式(BCM) BFC控制器,采用并行连接的180度反相输出进行控制,控制功率从300W到800W.和连续导通模式(CCM)技术不同,BCM使得升压二极管在零电流开关,因此降低了成本和损耗.可应用于100-1000W离线电源,大屏幕LCD-TV,PDP-TV,RP-TV的电源以及高端台式计算机和服输器点名源,获得80+证书的设备.本文介绍了FAN9612的主要特性,方框图,典型应用电路图以及采用FAN9612隔行扫描的BCM PFC电路图.

　　FAN9612: Interleaved Dual BCM PFC Controller

　　The FAN9612 Interleaved Dual Boundary-Conduction-Mode (BCM)

　　Power-Factor-Correction Controller operates two parallel-connected boost power trains 180º out of phase. Interleaving extends the maximum practical power level of the control technique from about 300W to greater than 800W. Unlike the continuous conduction mode (CCM) technique often used at higher power levels, BCM offers inherent zero-current switching of the boost diodes (no reverse-recovery losses), which permits the use of less expensive diodes without sacrificing efficiency. Furthermore, the input and output filters can be made smaller due to ripple current cancellation and effective doubling of the switching frequency.

　　The converters operate with variable frequency which is a function of the load and the instantaneous input / output voltages. The switching frequency is limited between 18kHz and 600kHz. The Pulse Width Modulators implement voltage-mode control with input

　　voltage feed forward. When configured for PFC applications, the slow voltage regulation loop results in constant on-time operation within a line cycle. This PWM method combined with the BCM operation of the boost converters provides automatic power factor correction.

　　The FAN9612 offers bias UVLO, input brown-out, input over-voltage, over-current, open feedback, overtemperature, output over-voltage and redundant latching over-voltage protections. Furthermore, the converters’ output power is limited independently of the input RMS voltage. Synchronization between the power stages is maintained under all operating conditions. The FAN9612 is available in Lead(Pb)-Free 16-lead SOIC package.

　　FAN9612主要特性:

　　Low Total Harmonic Distortion, High Power Factor

　　180°Out of Phase Synchronization

　　Automatic Phase Disable at Light Load

　　1.8A Sink, 0.8A Source, High Current Gate Drivers

　　Trans-conductance (gM) Error Amplifier

　　Voltage-Mode Control with (VIN)2 Feed Forward

　　Closed-Loop Soft-Start with User-Programmable Soft-Start Time for Reduced Overshoot

　　Minimum Restart Timer Frequency to Avoid Audible Noise

　　Maximum Switching Frequency Clamp

　　Brown-Out Protection with Soft-Recovery

　　Non-Latching OVP on FB pin and Latching Second Level Protection on OVP Pin

　　Open Feedback Protection

　　Over-Current & Power-Limit Protection for Each Phase

　　Low Start-Up Current of 80-μA Typical

　　Works with DC, 50Hz to 400Hz ac Inputs

　　FAN9612应用:

　　100-1000W Off-line Power Supplies

　　Large Screen LCD-TV, PDP-TV, RP-TV Power

　　High-End Desktop PC and Server Power Supplies

　　80-PLUS Certified Equipment

图1.FAN9612方框图

图2.FAN9612典型应用电路图

图3.采用FAN9612隔行扫描的BCM PFC电路图