A Flying-Inductor Hybrid DC–DC Converter for 1-Cell and 2-Cell Smart-Cable Battery Chargers

This article presents a new step-down hybrid converter topology that uses an input flying inductor and a switched-capacitor network to generate output voltages suitable for charging 1-cell (1S) or 2-cell (2S) batteries. The proposed topology relocates the inductor from the high-current output to the low-current input, while providing step-down conversion ratios that take advantage of the higher voltage settings of Universal Serial Bus Type-C (USB-C) power delivery (PD). Moreover, moving the inductor to the input allows the parasitic inductance of a USB cable to be utilized in place of a discrete inductor, that is, a smart-cable architecture, eliminating the need for on-board magnetics and reducing on-board power dissipation. The converter is implemented in 7.37 mm
²
of a 130-nm BCD process and provides two outputs with ranges of 3–4.2 V and 6–8.4 V from a 9V input. With a 1
$\mu \text{H}$
discrete inductor, the prototype achieves peak powers of 12.2W and 31.9W and peak efficiencies of 94.3% and 97.4% for each output, respectively. The prototype is also demonstrated in a smart-cable architecture to limit on-board dissipation to 630 mW while delivering 7.2W at the first output or 350mW while delivering 14.4W at the second output. Simultaneous data and power transfer and electromagnetic interference (EMI) tests are provided to support the feasibility of integration into a smart-cable architecture.