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A wireless magnetic resonance energy transfer system for micro implantable medical sensors.

Li X, Zhang H, Peng F, Li Y, Yang T, Wang B, Fang D - Sensors (Basel) (2012)

Bottom Line: The energy transfer efficiency of the four-coil system is greatly improved compared to the conventional two-coil system.In addition, the output current varies with changes in the distance.The whole implanted part is packaged with PDMS of excellent biocompatibility and the volume of it is about 1 cm(3).

View Article: PubMed Central - PubMed

Affiliation: School of Electronics and Information Engineering, Beijing Jiaotong University, Beijing 100044, China. lixiuhan@bjtu.edu.cn

ABSTRACT
Based on the magnetic resonance coupling principle, in this paper a wireless energy transfer system is designed and implemented for the power supply of micro-implantable medical sensors. The entire system is composed of the in vitro part, including the energy transmitting circuit and resonant transmitter coils, and in vivo part, including the micro resonant receiver coils and signal shaping chip which includes the rectifier module and LDO voltage regulator module. Transmitter and receiver coils are wound by Litz wire, and the diameter of the receiver coils is just 1.9 cm. The energy transfer efficiency of the four-coil system is greatly improved compared to the conventional two-coil system. When the distance between the transmitter coils and the receiver coils is 1.5 cm, the transfer efficiency is 85% at the frequency of 742 kHz. The power transfer efficiency can be optimized by adding magnetic enhanced resonators. The receiving voltage signal is converted to a stable output voltage of 3.3 V and a current of 10 mA at the distance of 2 cm. In addition, the output current varies with changes in the distance. The whole implanted part is packaged with PDMS of excellent biocompatibility and the volume of it is about 1 cm(3).

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Related in: MedlinePlus

The diagram of the standard CMOS rectifier.
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f6-sensors-12-10292: The diagram of the standard CMOS rectifier.

Mentions: The structure of the rectifier [25] used in this paper is depicted in Figure 6. This rectifier does not dissipate too much power through substrate leakage current and rectifier dropout voltage, and does not increase the risk of latch-up. It is important to protect the circuit against latch-up and substrate leakage, because the source nodes of the rectifying pMOS transistors in Figure 6 are connected to the coil terminals, which have large voltage variations at high frequency. The separated N-wells are the nodes that increase the risk of substrate leakage current. In order to control each separated N-well voltage, the transistors MP3-MP6 are added to MP1 and MP2 to connect the N-well to Vout, coil1, or coil2 whichever is at a higher potential. Besides, the higher substrate potential reduces the threshold voltage of MP1 and MP2. With the reduction of the threshold voltage, the power dissipation in the rectifier block decreases and the average rectified dc voltage available at the regulator input increases. Reducing the rectifier dropout voltage lowers the minimum receiver coil voltage, which in turn saves the required transmitted power or increases the maximum permissible coupling distance between the transmitter and receiver coils. The instantaneous voltage drop on the transistors of MP1 and MP2 can be found from:(15)VGS=/VDS/=/VTH/+2IDμCox(W/L)where ID is the drain current, μCox is the intrinsic transconductance, VTH is the transistor threshold voltage, and W and L are the transistor width and length. From Equation (15), the W/L value should be increased as much as the rectifier area consumption and its parasitic capacitance will permit us to lower the dropout voltage.


A wireless magnetic resonance energy transfer system for micro implantable medical sensors.

Li X, Zhang H, Peng F, Li Y, Yang T, Wang B, Fang D - Sensors (Basel) (2012)

The diagram of the standard CMOS rectifier.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472828&req=5

f6-sensors-12-10292: The diagram of the standard CMOS rectifier.
Mentions: The structure of the rectifier [25] used in this paper is depicted in Figure 6. This rectifier does not dissipate too much power through substrate leakage current and rectifier dropout voltage, and does not increase the risk of latch-up. It is important to protect the circuit against latch-up and substrate leakage, because the source nodes of the rectifying pMOS transistors in Figure 6 are connected to the coil terminals, which have large voltage variations at high frequency. The separated N-wells are the nodes that increase the risk of substrate leakage current. In order to control each separated N-well voltage, the transistors MP3-MP6 are added to MP1 and MP2 to connect the N-well to Vout, coil1, or coil2 whichever is at a higher potential. Besides, the higher substrate potential reduces the threshold voltage of MP1 and MP2. With the reduction of the threshold voltage, the power dissipation in the rectifier block decreases and the average rectified dc voltage available at the regulator input increases. Reducing the rectifier dropout voltage lowers the minimum receiver coil voltage, which in turn saves the required transmitted power or increases the maximum permissible coupling distance between the transmitter and receiver coils. The instantaneous voltage drop on the transistors of MP1 and MP2 can be found from:(15)VGS=/VDS/=/VTH/+2IDμCox(W/L)where ID is the drain current, μCox is the intrinsic transconductance, VTH is the transistor threshold voltage, and W and L are the transistor width and length. From Equation (15), the W/L value should be increased as much as the rectifier area consumption and its parasitic capacitance will permit us to lower the dropout voltage.

Bottom Line: The energy transfer efficiency of the four-coil system is greatly improved compared to the conventional two-coil system.In addition, the output current varies with changes in the distance.The whole implanted part is packaged with PDMS of excellent biocompatibility and the volume of it is about 1 cm(3).

View Article: PubMed Central - PubMed

Affiliation: School of Electronics and Information Engineering, Beijing Jiaotong University, Beijing 100044, China. lixiuhan@bjtu.edu.cn

ABSTRACT
Based on the magnetic resonance coupling principle, in this paper a wireless energy transfer system is designed and implemented for the power supply of micro-implantable medical sensors. The entire system is composed of the in vitro part, including the energy transmitting circuit and resonant transmitter coils, and in vivo part, including the micro resonant receiver coils and signal shaping chip which includes the rectifier module and LDO voltage regulator module. Transmitter and receiver coils are wound by Litz wire, and the diameter of the receiver coils is just 1.9 cm. The energy transfer efficiency of the four-coil system is greatly improved compared to the conventional two-coil system. When the distance between the transmitter coils and the receiver coils is 1.5 cm, the transfer efficiency is 85% at the frequency of 742 kHz. The power transfer efficiency can be optimized by adding magnetic enhanced resonators. The receiving voltage signal is converted to a stable output voltage of 3.3 V and a current of 10 mA at the distance of 2 cm. In addition, the output current varies with changes in the distance. The whole implanted part is packaged with PDMS of excellent biocompatibility and the volume of it is about 1 cm(3).

Show MeSH
Related in: MedlinePlus