A 0.025–0.45 W 60%-Efficiency Inductive-Coupling Power Transceiver With 5-Bit Dual-Frequency Feedforward Control for Non-Contact Memory Cards

A 0.025-0.45 W inductive-coupling power transceiver for non-contact memory applications is presented. To deal with sudden and large load variations and achieve high-efficiency, we propose a power transceiver with 5-bit feedforward control. Knowing that load patterns of a memory card have strong correlation with commands issued by a host, feedforward control is applied to minimize response times. To achieve 5-bit power levels, the proposed transceiver utilizes pulse-density modulation (PDM) and a multi-channel structure. Different operation frequencies are chosen for each channel to maximize power transfer efficiency. To further improve transceiver efficiency and enable high-speed operation, an active rectifier with a fast positive feedback is proposed. The test prototype demonstrates 40%-70% efficiency across all load conditions and 60% efficiency in average, which are over an order of magnitude improvements compared to prior arts.