| With the rapid development of implantable medical devices,it has become increasingly common to treat human diseases with implantable stimulators.In contrast to traditional drug therapy,implantable neural stimulation embeds circuits inside the human body and utilizes current stimulation to treat diseases,which has excellence of pertinence.In order to prolong the service life of the implanted circuit and reduce the temperature rise during the operation of the device,there are strict requirements on the power consumption and energy efficiency of the implanted circuits.Since the output stage of the stimulator has the highest power consumption in the whole device,it is very important to optimize the power consumption and energy efficiency of the stimulator output stage.In addition,as one of the power sources of implantable devices,the application of wireless power transfer in implantable devices is also very popular.The energy efficiency of wireless power transfer directly affects the loss and temperature rise during normal operation,so it is also necessary to optimize the efficiency of wireless power transfer.For the efficiency optimization of the output stage of the neural stimulator,a SEPIC converter is introduced in the output stage to dynamically adjust the stimulation voltage and reduce the power consumption of the current source.In addition,for the efficiency optimization of the SEPIC converter,adaptive gate width control technology is used to improve the energy efficiency of the converter in a wide range of load.In order to further improve the energy efficiency of the output stage,a new type of stimulation: high frequency stimulation is introduced.High frequency stimulation can eliminate the current source loss in the output stage,as well as the extra loss in multi-channel stimulation,which in turn greatly increase the efficiency.In view of the limited dynamic range in traditional high frequency stimulation,this paper proposes a dual-source non-overlapping high frequency stimulation to expand the output current range.Considering the wireless power transfer,the energy efficiency is related to the load resistance,and there exists optimal load resistance that maximizes the energy efficiency.In this dissertation,the technique of resistance transformation is proposed and realized by the rectifier,so that the system can achieve higher efficiency in a wide range of load.This dissertation finishes the optimization of energy efficiency of the implantable neural stimulator,including the optimization of the energy efficiency of the stimulation output stage and wireless power transfer.In the optimization of the stimulating output stage,the SEPIC converter is first optimized and tapped,and the taping process is CSMC 0.8?m BCD process.Test results show that when the supply voltage is 3.7V and the load resistance is 500?,the SEPIC output voltage can be 0.3V to 12 V,whose load current is 0.6 to 24 mA.When the load current is greater than 6mA,the efficiency is higher than 70%,with the highest efficiency of 78%.As for the high frequency stimulation,a PCB prototype circuit of dual-source non-overlapping high frequency stimulator is designed and verified.Test results show that the dual-source non-overlapping high frequency stimulation can double the output current range and enhance the efficiency by 40%.For the optimization of wireless power transfer,it is verified in the form of circuit simulation.The simulation results confirm that when the load resistance is 100?~1500?,and the coupling coefficient is 0.05~0.25,the resistance transformation can indeed effectively improve the efficiency of wireless power transfer. |
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