The complication rate after posterior fusion and instrumentation for degenerative lumbar scoliosis was 68%. Abundant blood loss was a significant risk factor for early perioperative complications. The improvement of Oswestry disability index was less in patients with late complications.

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This paper presents a full-CMOS Wireless Power Receiving Unit (WPRU) with high efficiency 6.78 MHz Active Rectifier and DC-DC Converter for magnetic resonant A4WP applications. The proposed high efficiency Active Rectifier with Delay Locked Loop (DLL) is a highly efficient receiver circuit intended for use in resonant wireless charging applications with a resonant frequency of 6.78 MHz. Each MOSFET of the proposed rectifier is turned on and off based on the AC input voltage.The delay between the AC input current and the AC input voltage due to the delays of internal blocks such as Voltage Limiter, Level Shifter, Gate Driver, and Comparator, will cause the reverse leakage current degrading the power efficiency. Thus, the proposed Active Rectifier adopts the Delay Locked Loop (DLL) to compensate for the delay caused by internal blocks, which leads to the removal of reverse leakage current and the power efficiency maximization. Moreover, to maximize power efficiency, Negative Impedance Circuit (Temperature (PVT) Variation to solve the efficiency reduction problem, especially by heat.This chip is implemented using 0.18 μm BCD technology with an active area of 3.5 mm x 3.5 mm.When the magnitude of the AC input voltage was 8.95 V, the maximum efficiencies of the proposed Active Rectifier and DC-DC Converter were 91.5 % and 92.7 %, respectively. The range of AC input voltage was 3 V -20 V, the efficiency of the Wireless Power Receiving Unit (WPRU) is about 80.86 %.

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