| At present,most portable electronic devices use primary batteries as their main power source,and the size of the battery limits the development of these electronic devices in the direction of miniaturization and microminiaturization.Some emerging ultra-low-power applications,such as wireless sensor nodes and implantable biomedical devices,use energy harvesters such as solar cells,thermoelectric generators,piezoelectric materials,etc.to extract energy from the surrounding environment to get rid of the battery-powered problem.However,the collected energy changes with environmental changes,resulting in that the output voltage of the energy harvester cannot be directly supplied with power,so a DC-DC converter is required for voltage conversion.The charge pump is one of the main branches of the DC-DC converter.Its circuit uses a capacitor as the energy storage medium for energy conversion.By automatically adjusting the internal MOS switch,it can easily achieve boost,buck or reverse pressure.In the standard CMOS process,it is easily and completely integrated inside the chip circuit.The purpose of this paper is to study and design a high-efficiency,reconfigurable charge pump circuit,which can be widely used in various energy harvesting and control energy harvesting systems.According to the change of the input voltage,the charge pump adaptively adjusts the switch array inside the circuit,thereby reconstructing the corresponding voltage conversion ratio(Voltage Conversion Ratios,VCR)to stabilize the output voltage,thereby improving the system efficiency.The main research content of this paper is summarized as follows: According to the input voltage and load changes,the feedforward control scheme based on VCR switching mode and the feedback control scheme based on pulse frequency modulation(PFM)are selected respectively,and the architecture is determined according to the system design index,then analyze and design,simulate and verify each sub-module circuit,and design the layout.The module circuits in the system mainly include: reconfigurable charge pump array,bandgap reference circuit,comparator,VCR selection circuit,error amplifier circuit,VCO circuit,two-phase non-overlapping clock signal generating circuit,etc.The innovation of this article mainly lies in how to design a reconfigurable charge pump array,and make it detect the input voltage and load changes,adaptively switch VCR and PFM modulation,so that the output voltage remains stable.All module circuits in this article are designed based on the 0.18μm CMOS process model and verified by simulation.The input voltage range of the charge pump system originally designed is 0.2-2.0V,the output voltage is typically 1.0V,the output voltage accuracy is ±5%,the maximum load driving current of the circuit is 2m A,the maximum voltage ripple is less than 10 m V,and the clock frequency range is It is 1.16-41 MHz,and the peak efficiency of the system can reach 76.6%. |
