This article proposes a reconfigurable single-stage regulating asymmetrical full-wave step-down rectifier (SDR) for fast wireless charging. The SDR is reconfigurable into a step-up power amplifier (SUPA) for device-to-device (D2D) wireless charging. The SDR and SUPA can have a direct connection with the battery without an additional voltage regulator module (VRM). With the single-stage structure, the transmitting (TX) and receiving (RX) ac voltages across the resonant coil can be boosted, which greatly reduces the coil currents and losses, improving the D2D charging power. A reconfigurable controller for the TX/RX mode selection, as well as the switching timing control, is designed. The chip is fabricated in 0.35-μm CMOS that contains 20-V devices. For the asymmetrical operation, one GaN device is used for the high current path. Also, zero-voltage switching (ZVS) is realized for all the power transistors with one small (180 nH in the 4015 package) power inductor. The bidirectional D2D WPT system achieves a maximum charging power of 5.1 W with a D2D total efficiency of 46.3% and a charging distance of 1.6 cm. Finally, the peak total efficiency is 51.4% with a charging power of 3.4 W and a charging distance of 1 cm.