| As the microelectronics industry and semiconductor technology has gotten progressive,micro-batteries are proposed as supplies to power various electronic devices,such as implantable electronic devices,which can be used to monitor,diagnose and treat personal health care diseases,such as nerve stimulators,pacemakers and cochlear implants.The energy of micro-batteries can be provided by energy harvesters,however,the common energy harvesters,such as thermoelectric generator,solar cells and wireless transmission merely generate dozens to hundreds of millivolts.Such low voltages are usually insufficient to directly power implantable electronics,so most energy harvesters require booster DC-DC converters to boost the voltage.As a result,the boosted voltage can be applied directly to power implantable electronic devices.The boost converter designed with a miniaturized and high coupling coefficient transformer has excellent circuit performance at low input.However,under the stable output voltage,the loss of power conversion at high input voltage is very large.The inductive boost converter not only occupies a large chip area,but also has electromagnetic interference in large inductor.The boost converter with charge pump design is a type of storage voltage converter in accumulating pure capacitor energy,and widely used in switching power supply circuits,because the circuit is relatively simple.For boost converters used in energy harvesting circuits,they must be able to work at low power supply voltages and adapt to the input voltage changes brought by the environment.A low-input voltage and high-power conversion efficient of charge pump system is proposed in this article.Among them,the ring oscillator circuit structure designed in this article is based on a standard inverter structure combined with a novel type of threelevel redundant inverter structure,using multi-level stacked technology and self-biasing technology.The ring oscillator not only can obtain a better switch resistance ratio under low power supply voltage,but also improves the response speed of starting vibration.The lowest working voltage of the ring oscillator designed in this article is 80 m V,and use a two-phase nonoverlapping clock circuit as the clock input of the three-stage gate crosscoupled charge pump circuit.When the ring oscillator provides the clock signal with an amplitude of 400 m V and a frequency of 400 k Hz for the three-stage gate cross-coupled charge pump circuit,the input voltage ranges of the three-stage gate cross-coupled charge pump is 50 m V-650 m V.Within this input voltage range,the voltage boosting capability of the charge pump meets the design requirements,and the output voltage ripple is less than or equal to ±10 m V.The charge pump circuit designed in this article adopts the pulse width modulation control method.The control circuit mainly designs the bandgap reference voltage source circuit,the PWM comparator circuit,etc.This control circuit helps to improve the stability of the charge pump output voltage and reduce the output voltage ripple. |
