A wide input range buck-boost DC-DC converter using hysteresis triple-mode control technique with peak efficiency of 94.8% for rf energy harvesting applications

Abstract

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 x 1.14 mm (1.767 mm(2)). The measured peak efficiency of the buck-boost DC-DC converter is 94.8%.