Optimal Frequency and Critical Soft Switching Control of DC/DC Converter

A critical soft switching technique is proposed to reduce the switching losses of a bidirectional DC/DC converter. The proposed method can improve the efficiency and the value of passive components will be largely decreased. The paper derives the boundary conditions of critical soft switching with the parameters of dead time and threshold current for existing typical SiC and GaN devices. Then, a controlling strategy is developed to estimate and optimize the total power losses of a synchronous DC/DC converter with variable frequency at the given average current and duty cycle. With the combination of critical soft switching and optimal frequency control, the efficiency can be largely improved in every operating point. A power loss curve comparison between the proposed method and hard switching shows that the proposed method can reduce the losses up to 40%. The theoretical results are verified in a rigorous testing procedure.