Enhancing Line Transient Response of a RHP Zero Constrained Buck-Boost Converter

In this article, an adaptive sawtooth height control (ASHC) circuit is introduced to enhance the line transient response of a non-isolated buck-boost converter (BBC). The dynamic performance of a BBC is significantly hindered by the presence of a right-half-plane-zero (RHPZ) in its control-to-output transfer function. This RHPZ leads to reduced bandwidth and consequently slower line and load transient responses, particularly in voltage mode control (VMC). The ASHC effectively mitigates these issues, even in the presence of an RHPZ. A detailed design methodology is presented, and a Type-III controller is developed to evaluate the closed-loop dynamic performance of the BBC. Both the ASHC and the Type-III controller circuits are cost-effective and easy to implement, utilizing straightforward control logic and a minimal number of discrete components. Simulation and experimental results are provided to validate the effectiveness of the proposed ASHC control scheme. The results clearly demonstrates the fast line transient response due to incorporation of the proposed ASHC circuit.