A Boost Converter For Ultra-low Voltage Energy Collection

Portable electronics and wireless sensor networks are widely used for their portability and low power consumption,however,how to power these devices has always been a technical challenge.Due to the difficulty of battery replacement and maintenance,the traditional battery-powered approach is not well suited for portable electronics and wireless sensor networks.It is of great significance for the development of electronic technology to study the switching converter which can replace the traditional battery.In this paper,a DC-DC step-up converter,which can be used for micro energy harvesting is designed.The switch converter has the advantages of starting at ultra-low voltage,simple structure and high conversion efficiency.A depletion NMOS and a transistor which turns ratio 1:100 composed self-oscillating start-up circuit and allows the overall circuit to operate normally at ultra-low voltages from 50 mV to 400 mV.The output of the converter is used as the power supply voltage of the sub circuit to realize the independent power supply system.A voltage feedback control circuit is used to adjust the output voltage,the feedback circuit’s working mode are controlled by voltage feedback method,in other time the feedback circuit does not work,which improves the efficiency of the converter and avoids over-voltage damage.The design uses VIS 0.45μm BCD technology,mainly design a start-up circuit,a bandgap reference,an error amplifier and a voltage comparator,startup function,feedback control circuit and conversion efficiency of the overall circuit are studied.In this paper,the Cadence software is used to simulate the performance of the designed step-up DC-DC converter and the design indicators of all sub-circuit and overall circuit are in accordance with the design requirements.The simulation results show that the converter in this design can work normally when the input voltage range is from 50 mV to 400 mV,and output a fixed voltage of 3 V,the output voltage ripple is below 20 mV;load current range from 1 1μA to 2 mA,the highest conversion efficiency can reach 48%.The design indicators of all sub-circuit and overall circuit are in accordance with the design requirements.