Control Strategy to Ensure Negative Offset Current for a Four-Switch Buck-Boost Converter Using Quadrangle Modulation

초록

With the recent development of electric vehicles and renewable energy, the demand for high-efficiency bidirectional DC-DC converters has been increasing. The Four-Switch Buck-Boost (FSBB) converter is considered one of the promising topologies due to its wide input/output voltage range and high power density. In FSBB converter, quadrangle modulation enables zero-voltage switching(ZVS) turn-on, improving efficiency and allowing an increase in switching frequency. However, despite these advantages, quadrangle modulation involves a complex control mechanism, and generating the negative offset current required for ZVS turn-on is challenging. Conventional approaches to generating the negative offset current require complex circuit configurations to determine the switching instant for generating the negative offset current. The presence of these complex circuits increases the overall system complexity, expands the control board size, and raises manufacturing costs. Moreover, since the current of the switch must be measured and utilized, implementing the required sensing hardware becomes challenging in high-power applications. Alternatively, the negative offset current can be controlled by using a look-up table. However, in such cases, parameter variations may prevent the offset current from accurately reaching its target value, which can lead to control instability and a reduction in system efficiency. This paper proposes a control method that generates the negative offset current using only inductor current sensing, along with a detailed design methodology and gain-setting approach for the controller.

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