Ecap-less 800V On-board Battery Charger Based on Unbalanced Half-bridge Split Capacitors Power Decoupling Circuit

This paper proposed an Electrolytic Capacitor-less (Ecap-less) 800V onboard charger (OBC) based on a Half-bridge Split Capacitors Power Decoupling (HSC-PD) circuit. A new design and control method proposed for HSC-PD to minimize the capacitance needed for the dc-link of the OBC enables the deployment of Film capacitors (Fcap) only. Both dc component and capacitance values of the decoupling capacitors are designed unequally with the bottom-bias capacitor approach, reducing not only equivalent capacitance and ac voltage ripple but the current rating of the PD circuit. An effect of fourth-line frequency harmonics caused by the double-line frequency of voltage and current in the PD circuit is also analyzed. The feedback control developed for HSC-PD based OBC system considering the proposed unequal dc component and capacitance. The impact of the DC offset ratio discussed for the converter efficiency and experimental results demonstrate the superiority of the proposed method.