临界模式功率因素校正变换器的建模

Modeling of power factor corrector in boundary conduction mode

在临界模式下,功率因数校正变换器的开关频率与占空比跟随输入电压变化,使用状态空间平均的方法对其建模时,线性化过程中确定静态工作点存在困难。对此提出了一种新的建模方法,首先建立输入输出电压、电压环路输出及输出二极管电流约束关系,通过对约束项在半线电压周期内作平均化处理,消除输入电压与二极管电流两个时变量影响,得到新的平均化约束方程,然后经过线性化处理得到小信号模型。设计了一个30 W反激变换器样机以验证提出的建模方法。实验结果与理论数据表明,该小信号模型可以很好地描述功率因数校正变换器的动态特性。

Modeling power-factor correction converters operation in a boundary conduction mode with state-space-averaging technique is suffered from determining the quiescent point in linearization, because duty ratio and the switching frequency of BCM converter vary with the input voltage. A novel modeling technology is presented for those converters. Firstly, constructing the rela- tion among input voltage and output voltage, control loop output and the current of output diode, taking average in half the line voltage cycle to eliminate the input voltage and the diode current two variables affect, then getting a new average amount of con- straint equations. Small-signal model can be derived by linear the new constraint equations. The performance of the proposed mod- eling approach is evaluated on a flyback 30 W. The experimental results and theoretical data prove that the model describes the dynamic characteristics of the circuit well.