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This study presents the design and implementation of a 6.78 MHz wireless power transfer (WPT) system that uses magnetically coupled resonance for 5 W mobile phone charger applications. For a resonant WPT system, one of the most significant design issues is the power receiver because of its resonant characteristics. A compact resonant-type power receiver is required for high efficiency and robustness. To realise a compact size, a fully integrated 5 W power receiver that includes an on-chip AC-DC converter and a DC-DC converter is implemented. A protection circuit that operates only during initial power-up is proposed to protect the power switches in the receiver. The proposed receiver was implemented using a 0.18 µm bipolarcomplementary metal-oxide-semiconductor-double-diffused metal-oxide-semiconductor process with a die area of 3.5 mm × 3.5 mm. The measured maximum power transfer efficiency of the receiver and peak efficiency of the system was 81 and 51%, respectively.

This paper presents a capacitor-less low-dropout (LDO) regulator for on-chip mobile applications. An additional push-pull current with a capacitive coupling circuit is proposed to significantly enhance the transient response of the LDO regulator. The proposed LDO regulator can deliver an output current of 100 mA with a minimum dropout voltage of 0.4 V. The circuit was modeled and implemented in a 0.35-µm CMOS process with a die area of 0.22 mm 2 . The experimental results show that the LDO regulator can be recovered within 0.5 µs at a voltage spike less than 90 mV.

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