This paper presents a wide range buck-boost direct current to direct current (DC-DC) converter for wireless power transfer (WPT) systems. To implement the wide range DC-DC converter, a Hysteresis triple-mode selector is proposed and designed to effectively adjust the DC-DC converter to operate in one of the three modes: buck, boost or buck-boost, according to the input voltage level. Hysteresis control technique eliminates the unstable state at the mode transition. An output soft start-up circuit is proposed to reduce the inrush current in the switch transistor. A min-max duty generator is introduced to improve the accuracy of DC-DC converter. When the output voltage is too low or too high in comparison to the desired value. The min-max duty generator can control the DC component of the error signal to eliminate the unwanted dead state of the pulse width modulation signal. In addition, only one external inductor is shared between two power stages, thus minimizing the system cost by reducing the external components. The proposed buck-boost DC-DC converter is implemented using 180 nm Complementary Metal-Oxide-Semiconductor (CMOS) technology. The output voltage is regulated to 5 V when the input voltage ranges 3-8 V, and output load current ranges 100-500 mA. The die area is 1.55 mm × 1.14 mm (1.767 mm 2). The measured peak efficiency of the buck-boost DC-DC converter is 94.8%.
An efficient synchronous active rectifier and Multi Feedback low drop out (LDO) Regulator coupled with a wireless power receiver (WPR) is proposed in this study. An active rectifier with maximum power conversion efficiency (PCE) of 94.2% is proposed to mitigate the reverse leakage current using zero current sensing. Output voltage and current are regulated by multi-feedback LDO regulator, sharing the single path transistor. The proposed chip is fabricated in the 0.18 µm BCD technology having die area of 16.0 mm 2 . A 94.2% power conversion efficiency with the load current of 800 mA is measured for the proposed active rectifier.
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