Study And Design On Biomedical High-efficiency Magnetic Resonance Wireless Power Transceiver

With the rapid development of smart medical and smart health,wireless power transfer technology applied to wearable/implantable biomedical device has significant research value.The existing way of wireless power transfer can divide into magnetic resonance,magnetic induction,electric field coupling,microwave radiation and ultrasonic.Among them,the magnetic resonant has been widely used in biomedical device due to its long transmission distance,strong diffraction,low radiation,wide power coverage and broadcast power supply Considering the mobility and safety of living organisms and the space limitations of implantable device,magnetic resonant wireless power transfer technology has technical challenges in output power,efficiency,transmission range and volume.In this thesis,a system solution for high-efficiency and high-integration magnetic resonant wireless power transfer is proposed.Based on this solution,two sets of wireless power transceiver systems have been developed:for high-power applications,a boost high-power wireless power transceiver system based on feedforward constant voltage/constant current control is proposed,to solve the boost structure loop stability problem;for low-power applications,a wide-range low-power wireless power transceiver system that automatically tracks the split frequency is proposed,to achieve a wide coupling range and load range.Based on the 0.18?m CMOS process,the key chips of the above two systems have been verified.1.The proposed boost high-power transceiver system chip integrates high-efficiency differential Class-D power amplifier,series resonant active rectifier,and feed-forward constant-voltage/constant current control DC-DC converter.The measured results show that when the operating frequency is 6.78MHz and the transmission distance of 15mm,the maximum output voltage is 4.2V,the maximum output power is 1.6W,rectification efficiency is 94.94%,power conversion efficiency is 85.44%,and the overall system efficiency is53.82%.The chip area of transmitter and receiver is 0.59mm~2 and 0.65mm~2,respectively.This system complies with the A4WP charging standard,it also meets the power supply requirements of high-power biomedical devices such as decanters and artificial hearts.(1)By combining a rectifier and a boost DC-DC converter,a new power receiver topology is proposed.It constructs a feed-forward control mechanism,and innovatively utilizes the characteristics that the output current of the front stage does not change with the load and charging time,to generate the DC-DC duty cycle.This topology eliminates the traditional output current detection and feedback mechanism.It not only ensures the stability of the control loop,but also realizes wireless constant voltage/constant current charging.(2)A reverse current compensation for series resonant active rectifier is proposed.By introducing an offset voltage at the input of the comparator,the reverse current is compensated and the power conversion efficiency is improved.Simultaneously,considering over-compensation problem,a logic control circuit that inhibits multiple conduction is introduced,to achieve efficient and reliable power receive.In addition,this technology can also be used in parallel resonant active rectifier.2.The proposed wide-range low-power transceiver system chip integrates a constant voltage transmitter that automatically tracks the splitting frequency,an automatic amplitude control circuit and a parallel resonant active rectifier.The measured results show that the operating frequency is 1?13.56MHz,under the 500?load,the transmission efficiency remains 80.15%,the maximum conversion efficiency is 90.94%,and the maximum output power is 24.59m W,within the distance range of 5?15mm.When the distance is 10mm,within the load range of 50?1000?,the output voltage remains 3.7V,and the maximum output power is 129.7m W.The chip area of transmitter and receiver is 0.31mm~2 and 0.37mm~2,respectively.This system meets the power supply requirements of low-power biomedical devices such as brain electricity acquisition and visual prosthesis.(1)Based on the circuit and coupled mode model,the theoretical mathematical relationships of transmission efficiency,output power,input-output voltage ratio verse coupling distance and load are established,respectively.Both theoretical results show that the transmission condition for wide coupling and wide load range is that the operating frequency equals to the splitting frequency.The consistency of the theoretical results further demonstrates the correctness of the transmission conditions(2)A new coil drive method based on the inductor capacitor oscillator structure is proposed,as well as a power and efficiency adaptive regulated mechanism without the traditional power amplifier,additional power adjustment,and maximum efficiency tracking circuit.At the same time,automatic amplitude control is introduced in the output of the oscillator to ensure a constant transmission voltage.When the coupling distance or load changes,using the transformer-coupled dual-mode oscillator works at the splitting frequency characteristics,the system automatically adjusts the operating frequency to the splitting frequency.On the one hand,it ensures that the transfer efficiency and output power are maintained within a wide coupling range;On the other hand,it ensures that the output voltage is constant within a wide load range.The two wireless power transfer systems are introduced in this thesis can not only meet the different power supply requirement of biomedical devices,but also provide some technical reference for wireless electricity transfer,simultaneous wireless information and power transfer.