谷值电流控制三电平Buck变换器

Research on three-level Buck converter with valley current control

三电平Buck变换器能使开关管的电压应力减小为输入电压的一半,使电感电流脉动频率为开关频率的两倍,减小滤波器的尺寸。为了实现以上的优点,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。为此,采用谷值电流控制的方法,通过平衡电感电流来调节飞跨电容上的电压,实现飞跨电容电压稳定。建立三电平Buck变换器谷值电流控制的小信号模型,以获得小信号传递函数模型,进而对其补偿网络进行了设计。仿真验证了理论的正确性和控制策略的可行性。

The throe-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 at half of the input voltage. Valley current control method was adopted to balance the voltage of flying capacitor by balancing the inductor current. The small-signal model was established to obtain the transfer function, which made it possible to design the compensation network. The simulation results prove that the theoretical analysis is correct and the control strategy mentioned above is feasible.