低占空比谷值电流控制三电平Buck变换器研究

Research on Three Level Buck Converter with Valley Current Control at Low Duty Ratio

为了实现三电平Buck(Buck TL)变换器使开关管的电压应力减小为输入电压的一半、电感电流脉动频率提高为开关频率的两倍以减小滤波器的尺寸的优点,使变换器具有较高的功率密度,必须保持飞跨电容的电压为输入电压的一半。因此,基于谷值电流控制方法,建立Buck TL变换器的小信号模型,获得了小信号传递函数,然后对其补偿网络进行设计,以实现对电感电流的控制。最后,将电流控制模式和电压控制模式进行了比较,仿真验证了电流控制模式的优越性。理论分析的正确性和控制策略的可行性也得以证实。

The three-level buck converter can reduce the voltage stress of switch to half of the input voltage,double the effective switching frequency and decrease the size of filter. To achieve the advantages mentioned above and high power density,the voltage of flying capacitor must be balanced to half of the input voltage. Because inductor current contains the information of flying capacitor voltage,the voltage of flying capacitor can be stabilized by adjusting the inductor current. Therefore,the small-signal model was established to obtain the transfer function based on valley current control method. Then the compensation network was designed to control the inductor current. At last,the current control mode was compared with the voltage one,the former＇s superiority was verified,and the correctness of theoretical analysis and the validity of control strategy were proved by the simulation results.