Analysis and Modeling of an FFHC-Controlled DC–DC Buck Converter Suitable for Wide Range of Operating Conditions

To achieve the best optimized performance in terms of stability and dynamic behavior of power electronic converters, it is necessary to use a more advanced control technique and accurate mathematical model. This paper proposes a fixed-frequency hysteretic current (FFHC) controller that uses both sliding-mode control (SMC) technique and fixed-frequency current controller with a hysteresis band to achieve all properties of the variable structure controller. However, realizing such fixed-frequency sliding-mode controller using small-signal-averaged (SSA) model of the power converters and Utkin´s equivalent control technique may not be valid for all conditions. We show that it can be applicable only when the fast-scale dynamics of the converter system is stable, which can be achieved successfully by analyzing the stability of the FFHC-controlled buck converter using Filippov method and Floquet theory. The regions of stability are then presented to show the domains of existence of nominal period-1 and higher periodic orbits in 2-D parameter space. We also demonstrate how to derive the equivalent control law from the modified tristate converter topology to design the controller. Finally, the experimental results are presented to validate the effectiveness of this hybrid FFHC controller.