Unbalanced Half-Bridge Split Capacitor Power Decoupling With Multiorder Frequency Control for 800-V On-Board Battery Charger

This article proposes a new method for the design and control of a half-bridge split capacitor-based power decoupling (HSC-PD) circuit to eliminate the bulky electrolytic capacitors (E-caps) at dc-link, targeting 800-V on-board battery charger (OBC) applications with higher reliability and power density. In the proposed method, both capacitance and dc-offset voltage of the decoupling capacitors are designed unbalanced with the bottom capacitor having a dominant effect over the top one, which reduces the decoupling capacitance requirements compared to the previous works. In addition, the effect of lower dc-link capacitance in reducing power rating of the precharge resistor, typically used in OBC applications, is presented. This effect, overlooked in previous literature, leads to reducing volume and cost of the OBC. A small signal model of the HSC-PD is introduced, and a modified feedback control strategy is proposed, offering lower memory usage and calculation effort for the digital signal processor (DSP) microcontroller when compared with conventional proportional resonant (PR) controllers. The comparisons of the proposed method with other HSC-PD counterparts as well as with the conventional E-cap method are given. Finally, a 7.4-kW prototype of an 820-V interleaved totem-pole power factor correction (PFC) with an HSC-PD is built and tested to verify the superior performance of the proposed method.