| The batteries do not have to be replaced frequently in wireless sensors,wearable electronic devices,and Internet of Things(Io T)devices powered by environmental energy,reducing the cost of these devices.Therefore,there has been much interest in environmental energy harvesting techniques.Single source energy harvesting systems have limited applications,while this shortcoming can be overcomed well by multi-source energy harvesting systems.The uneven energy from transducers can be stored into a battery and converted to a stable voltage to power the load through the power management system for a long time operation of the system.In this thesis,a multi-source energy harvesting power management chip that can effectively harvest both piezoelectric and photoelectric energy simultaneously is designed in the 0.6μm HV CMOS technology.The multi-source energy harvesting power management chip designed in this thesis can mainly be divided into three parts: an optoelectronic global maximum power tracking circuit,a piezoelectric interface circuit,and a DC-DC converter.In order to reduce the impact of shadows on the harvesting of light energy by solar panels,the photoelectric global maximum power tracking circuit adopts a timed scanning method for maximum power tracking.The input power under different optoelectronic input voltages is compared in the global maximum power tracking circuit through the pulse integration method,improving the accuracy of optoelectronic maximum power tracking.The simulation results show that the maximum power tracking of optoelectronics can still be achieved even when there are multiple extreme points in the P-V curve,and the maximum tracking accuracy of the maximum power tracking circuit can reach 99.9%.A capacitor synchronous switch structure that can efficiently harvest piezoelectric energy,converting the input AC power of the energy source into DC power is adopted in he piezoelectric interface circuit.To improve the efficiency of capacitor voltage flipping,the proposed piezoelectric interface circuit improves the switch array by connecting the flipped capacitor between the input source and ground,reducing the number of switches and cutting the driving loss of the switch during each voltage flipping.Additionally,a voltage selection circuit is used to ground the lower voltage in the input source to prevent the switch from being misled.The detection results of the peak detection circuit in the designed piezoelectric interface circuit are used not only to control the flipping of capacitor voltage,but also to control the switches which replace the diode to achieve energy source charging of the load,reducing the energy loss of the circuit.The simulation results show that the proposed piezoelectric interface circuit not only achieves a voltage flip efficiency of74%,but also can achieve self starting under the circumstance of a piezoelectric input with a minimum open circuit voltage of 2.2V.On this basis,an efficient DC-DC converter with low static power consumption to power the load is proposed in this thesis.A voltage up and down structure is adopted in the converter,which improves energy utilization by matching the difference between input and output power dynamically through the method of storing excess charges in the battery.At the same time,the converter expands the output power range by adjusting the switch conduction time and switch operating frequency,reducing switch drive losses under heavy loads,reducing output ripple and reducing transmission losses under light loads.Moreover,when the input and output power is low,the circuit will switch into the sleep mode by the control of the converter,which reduces the static power consumption of the circuit and achieves long-term operation of the system.Finally,the overall layout of the system was drawn and post simulated.The post simulation results indicate that the static current of the system during normal operation is 7.6μA.When the input and output power get lower,the system switches into sleep mode,reducing the quiescent current to 3μA.The maximum energy harvesting efficiency of the system can reach 91.6% when harvesting both piezoelectric and optoelectronic energy simultaneously. |
