Effects of Different Control Methods on the Buck-Buck Cascaded System

Control methods often play important roles in the converters to improve characteristics. This paper takes the buck-buck cascaded system as an example to study the influence of different control methods on the system's performance especially for stability and dynamic response. Different from the stability evaluation method of the cascaded system discussed in the previous literature, this paper studies a more complex situation, when the front stage converter operates with the sub harmonic oscillation and connected with a buck converter. Besides, to evaluate the transient performance with different control methods, four transfer functions are proposed. Finally simulations verify the above analysis. It indicates that three basic control methods which are voltage control, peak current mode control and V2 control perform similarly in term of the stability, and as for the transient performance, when V2 control is adopted to the both converters of the studied system, the cascaded system has a better transient performance compared to the other two basic control methods.