A Bidirectional USB Power Delivery Voltage-Regulating Cable

The development of fast charging technology has significantly reduced the charging time for devices. However, with the increase of power level, the thermal and size issues become the limiting factors for fast charging, especially for compact devices. This article presents the concept of the voltage-regulating cable (VRC) which integrates the charging IC and all the associated passive components into the universal serial bus (USB) cable connector. By relocating the power converter and its associated heat from the devices to the cable, this design significantly reduces the device size and provides an alternative solution for the overheating issues. The VRC can regulate a bidirectional step-down voltage for two kinds of typical application scenarios: adapter-to-device (A2D) and device-to-device (D2D) scenarios. In addition, a symmetrical VRC structure is also proposed to facilitate a reversible and user-friendly connection. The designed VRC prototype, fabricated in 180-nm high-voltage BCD process, occupies an area of $4.7\times 2.9$ mm2, including all passive components. It achieves a peak power density of 3.17 W/mm2 when transferring the maximum power of 42 W in the A2D scenario and a peak power density of 1.36 W/mm2 with a maximum power of 18 W in the D2D scenario.