A Step-Down Series-Parallel Dual-Resonant Switched-Capacitor Converter With Extended Voltage Gain Range and Complete Soft Charging

In this article, a step-down series-parallel dual resonant switched-capacitor converter (SP-DRSCC) is proposed to address issues of traditional SCC, such as high transient current spikes, inherent capacitor charge-sharing losses, hard-switched operation, and so on. The dual-resonant-core (DRC) is added to the traditional SP switched-capacitor-converter (SCC) and the on-time fixed frequency modulation is adopted. With the DRC and on-time fixed frequency modulation, a “charge balance” state with overlapping resonant currents is created, enabling the SP-DRSCC to regulate its conversion ratio continuously, widely, and effectively, even under light load conditions. Additionally, the converter achieves zero-current-switching (ZCS) turn-on for transistors and ZCS turn-off for diodes. Furthermore, the synchronous SP-DRSCC with only two GaN active switches, called the hybrid SP-DRSCC, is proposed to reduce high-frequency ringing and conduction loss, which makes it suitable for applications in data centers and micro satellites. The analysis of the operation principles, voltage-gain curves, and component stress is presented comprehensively. The effectiveness of the proposed topology, modulation strategy, and circuits is validated through a 3X step-down SP-DRSCC prototype, with a maximum power of 100 W and nominal input and output voltages of 48 V and 12 V, respectively.