Energy-Harvesting Circuits With a High-Efficiency Rectifier and a Low Temperature Coefficient Bandgap Voltage Reference

In this paper, a high-efficiency rectifier and a low temperature coefficient (TC) bandgap voltage reference (BGR) in energy-harvesting circuits are presented. The audio signal generated from smartphone is used to verify the energy-harvesting circuits that are composed of a full-wave low-voltage active rectifier, a low-dropout (LDO) regulator, and a current-mode BGR circuit. An active diode and a proposed AVC are presented to enhance the rectifier efficiency. The rectifier output voltage is regulated by an LDO close to a stable 1.2-V supply voltage in a 0.18- $\mu \text{m}$ 1P6M Taiwan Semiconductor Manufacturing Company standard complementary metal–oxide–semiconductor (CMOS) process. A curvature-compensation technique is proposed to improve the TC of the BGR, and the best TC of 15.33 ppm/°C between the temperature range of −10 °C and 120 °C is measured. The measured rectifier achieves the maximum power conversion efficiency (PCE) of 87.2% under $1.77~V_{\mathrm {pp}}$ ac input signal with 2- $\text{k}\Omega $ output load resistance. The measured results demonstrate the better characteristic of the rectifier and BGR than that of previous works using the low-power structure.