Implementation of Time Division Multiplexing With Commercial Flyback Controller for Multi-Outputs USB Power Delivery Charger

Universal serial bus power delivery (USB-PD) chargers are more attractive to consumers with multiple output ports where more devices can be charged simultaneously. Existing multiple-port charger designs take multi-stage approaches, which increases power loss, charger size, and cost. This paper addresses this issue by presenting a time-division multiplexing (TDM) quasi-resonant (QR) flyback converter that eliminates the buck converter stages with simple and commercial analog implementations without the need of microprocessors. The circuit operation and practical design considerations are discussed in detail. An universal AC input, dual-USB-C GaN prototype validates the concept, while demonstrating USB-PD compliant operation, passed conducted EMI, and superior efficiency which passes the most stringent efficiency standards with margin where the benchmark GaN charger fails. Thanks to the elimination of buck stages, the proposed dual-USB-C charger achieves 1.9 W/cm
$^{3}$
uncased power density, close to that of single-USB-C charger.