Design And Study On Transcutaneous Energy Transmission System Based On Class D Power Amplifiers

With the application of micro-bio-medical equipment in medical, transcutaneous energytransmission is being paid more and more attention. It can not only as a supplement to thebattery-powered technology, and can be used as an independent technical alternative to bat-tery-powered, breaking through the bottlenecks of the power supply of micro-biomedical de-vice. Transcutaneous energy transmission providing stable energy supply, solving limitedenergy resources of batteries, and avoiding the risk of battery electrolyte leakage, thus becomea hot research point in the implantable circuit.Transcutaneous energy transmission is based on the mutual inductance coupling theory,using Class E power amplifier as traditional basic circuit, but this structure suffer from shortdistance, low efficiency, energy excess emission. In this paper, coupling structure, transmittercircuit and feedback control as entry points, the goal is to design long-term implanted tran-scutaneous energy transmission system, which provides safe energy supply and means ofcommunication for micro-bio-medical equipment, in shallow organization. The design systemconsists of an external transmitter and receiver circuits in vivo. The transmitter circuit in-cludes signal source, power amplifier, LSK demodulator, MCU for feedback control, digitaladjustable power. The receiver circuit consists of rectifier, linear regulator, PWM modulatorand LSK modulator.This paper first analyzed the mutual inductance coupling theory and the strongly coupledmagnetic resonances theory, and deduced a three-coil coupling structure. It compensates forthe mutual inductance coupling efficiency decrease rapidly with the distance increase, whileavoid using the complexity receiver structure of the strongly coupled magnetic resonances.Then, it compares to Class E and Class D power amplifier theory, combines with the charac-teristics of the transcutaneous energy transmission, and concludes that Class D power am-plifier is more suitable for transcutaneous energy transmission. Next, it realized two-waycommunication, and designed a new low-complexity dual-loop feedback structure, which im-prove safety of power supply for implanted circuits. The energy situation is sent to the trans-mitting circuit using the PWM method, adjust the transmit power, and change the ener- gy-harvesting capacity of the receiving coil, which constitute the dual-loop feedback. Com-pared with the current feedback using in transcutaneous power transmission, it reduces theAD or power detection module, so that the implanted circuit complexity is reduced. Finally, atranscutaneous energy transmission system with energy feedback control, which is based onClass D power amplifier, is designed and implemented.System test result show that the energy transfer distance is0cm to4cm, with the abilityto automatically adjust the transmit power within the effective range. The implanted circuitcan receive the maximum power is246mW. The transcutaneous energy transmission systemand bladder stimulator constitute the implantable system, and experiments in adult beagledogs. The experimental results show that the proposed structure can independently provideenergy for the micro-bio-medical equipment.