Implantable Nerve Electrical Stimulator System Circuit And Chip Design

Today,implantable electrical stimulation has been widely used and has achieved very good results.Implantable electrical stimulation refers to implanting circuit devices into specific parts of the human body and treating them by current stimulation.Compared with traditional drugs or physical therapies,implantable electrical stimulation can be treated more specifically,and bring more comfort to patients.Implantable electrical stimulation system is generally powered by batteries,in order to reduce the risk of surgery and trauma caused by battery replacement,the use of wireless rechargeable batteries is an inevitable choice.Therefore,wireless energy transmission technology is especially important in implantable stimulation systems.The efficiency directly affects the loss during wireless charging and the temperature rise of the battery.In addition,the power consumption of the stimulus output stage is as important as the wireless charging,which will determine the length of time the implantable system can operate after each charge,while also affecting the heat consumption during stimulation.For the wireless charging in the implanted system,this paper adopts the constantcurrent and constant-voltage charging and introduces the closed-loop control to dynamically adjust the charging voltage so that it always maintains a small differential pressure with the battery voltage.In addition,for the efficiency optimization of the closed-loop control,a high-efficiency rectifier circuit and a switching power transistor are designed,and a corresponding constant-current and constant-voltage charging controller is designed.The common control method is adopted to ensure smooth conversion of each charging phase.For the stimulus output in the implanted system,the SEPIC(Single Ended Primary Inductance Converter)structure is used to dynamically adjust the output voltage,and combined with the current feedback method to avoid current source loss.In addition,this paper designs a new hysteresis comparison control method based on the enabled oscillation mode.Compared with the traditional PWM(Pulse Width Modulation)control or hysteresis comparison control,the control method has very small current recovery time,only about 2.5us.It can realize the advantages of buck and boost output at the same time,and directly control the output ripple.At the same time,the switching power transistor is carefully simulated,and the optimal size is selected to optimize the efficiency.The wireless charging module has been fabricated in 0.8um HV process to verify the above design method.The module can achieve 2.8-4.4V wireless charging,charging current up to 60 m A,and charging efficiency is more than 70%.The stimulus output module is designed with a PCB prototype circuit for test verification.It can output 0-12 m A current,load range up to 200-3000?,ripple control within 10%,and efficiency is more than 75%.In the end,the two parts of the circuit and the connection part are integrated into a single-chip system,and it is fabricated in 0.25 um HV process.At present,the layout design and post-version verification have been completed.