On Semi NCP1631交错式2相功率因数控制方案

    On Semi 公司的NCP1631是交错式2相功率因数控制器,具有接近1功率因数,2个小段相对1个大段，减小元件尺寸，改善散热;它的频率钳位临界导电模式(FCCrM)及频率反走技术线性降低钳位频率成为功率的函数，优化负载范围内的能效,180°相移输出大幅减小电流纹波，减少电磁干扰(EMI)及降低大电容均方根(rms)电流, 非常适合平板电视及超薄笔记本适配器.本文介绍NCP1631主要特性, 功能方框图, 电流检测方框图和零电流检测图, 振荡器方框图以及典型应用电路图.

    NCP1631:Interleaved, 2-Phase Power Factor Controller

    The NCP1631 is a controller for use in 2-phase interleaved power factor correction pre-converters. Interleaving consists of paralleling two small stages in lieu of a single big stage. This approach has several merits like ease of implementation, ability to use smaller components, and better distribution of heating. These attributes make the interleaved PFC topology attractive to slim form factor applications such as flat panel TVs and ultra-slim notebook adapters. Interleaving can also extend the power range of Critical Conduction Mode, which is an efficient and cost-effective (no need for low trr diodes) operating mode. The NCP1631 operates in Frequency Clamped Critical Conduction mode (FcCrM). The circuit utilizes frequency foldback to linearly decay the clamping frequency as a function of power. As a result, the NCP1631 provides optimized efficiency across the load range. In addition, the NCP1631 drivers exhibit a 180 phase shift for a significantly reduced current ripple, which lowers EMI and reduces the rms current in the bulk capacitor. The NCP1631 incorporates all the features necessary for building robust and compact interleaved PFC stages, with a minimum of external components. Available in SOIC-16 package.

    NCP1631主要特性:

    Near?Unity Power Factor

    Substantial 180 degree Phase Shift in All Conditions Including Transient Phases

    Frequency Clamped Critical Conduction Mode (FCCrM) i.e.,Fixed Frequency, Discontinuous Conduction Mode Operation with Critical Conduction Achievable in Most Stressful Conditions

    FCCrM Operation Optimizes the PFC Stage Efficiency Over the Load Range

    Out?of?phase Control for Low EMI and a Reduced rms Current in the Bulk Capacitor

    Frequency Fold?back at Low Power to Further Improve the Light Load Efficiency

    Accurate Zero Current Detection by Auxiliary Winding for Valley Turn On

    Fast Line / Load Transient Compensation

    High Drive Capability: ?500 mA / +800 mA

    Signal to Indicate that the PFC is Ready for Operation (“pfcOK” Pin)

    VCC Range: from 10 V to 20 V Safety Features

    Output Over and Under Voltage Protection

    Brown?Out Detection with a 50?ms Delay to Help Meet Hold?up Time Specifications

    Soft?Start for Smooth Start?up Operation

    Programmable Adjustment of the Maximum Power

    Over Current Limitation

    Detection of Inrush Currents

    NCP1631典型应用:

    Computer Power Supplies

    LCD/Plasma Flat Panels

    All Off Line Appliances Requiring Power Factor Correction

    图6.NCP1631典型应用电路图