A FREQUENCY CONTROL METHOD FOR REGULATING WIRELESS POWER TO IMPLANTABLE DEVICES
Presented By:
SREESYAM K
S7 AE
No:65
College Of Engineering, Trivandrum
2007-11 batch
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CONTENTS
Objectives
Need of Wireless Power Supply (WPS)
Architecture of WPS
Circuit Diagram of WPS
Analysis of Frequency Control
Switched Capacitor Control
Conclusion
References

OBJECTIVES
Study the architecture of WPS
Analysis of power flow against frequency
Presents a method to regulate the power by adjusting resonant frequency

WHY WPS?
Supply energy for indefinite period
Avoids risk of infection
No reliability problems

WPS WORKING
Use magnetic field for energy transfer
High frequency ac current produced in primary coil
Secondary coil gets power by electro magnetic induction

CLOSELY COUPLED WPS
NEED OF POWER REGULATION
Power varies due to loose coupling
Power transfer depends on match b/w resonant frequencies
Coupling conditions varies because of day-to-day activities
Power variation causes tissue heating & device damage

WHY REGULATION AT PRIMARY?
Power dissipation at the implant lead to tissue heating
Components require for regulation increase physical size
Voltage magnitude regulation is efficient only at full tuning

ARCHITECTURE OF WPS
Primary coil placed outside & driven by push pull converter
Secondary coil implanted under the skin
Coupling coefficient varies in the range 0.1 - 0.3
EXTERNAL PRIMARY
IMPLANTABLE SECONDARY
ANALYSIS OF POWER FLOW AGAINST FREQUENCY
CURRENT & VOLTAGE WAVEFORMS
Contd..
Contd..
Contd..
Relationship between frequency & power
Relationship between phase & frequency
ZERO LOAD CONDITION
F1 & F2 are boundary frequencies to maintain constant output
Operation between F1 & F2 causes high power dissipation
Operate at frequency under F1 or over F2
Contd..
SWITCHED CAPACITOR FREQUENCY CONTROL
Capacitors at the input port of resonant tank are controlled by hard switching of MOSFETS
Frequency variation can’t be smooth
Causes switching losses
Produces surge current ,that may damage the device

ALTERNATIVE
Variable capacitance controlled by soft switching a capacitor with varied duty cycle
No destructive surge current
Less switching losses
Frequency range is determined by total capacitance
PUSH- PULL RESONANT CONVERTER
PHASE CONTROL METHOD
Contd..

CONCLUSION
Discussed power regulation method based on frequency control
Relationship between power & frequency derived
Explained phase control method to vary frequency

REFERENCES
H. Maki, Y. Yonezawa, E. Harada, and I. Ninomiya, “An implantable telemetry system powered by a capacitor having high capacitance,” in Proc. 20th Annu. Int. Conf. IEEE Eng. Med. Biol. Soc., Oct. 2008, vol. 4, pp. 1943–1946.
A. S. Berson, “Magnetic control and powering of surgically implanted instrumentation,” IEEE Trans. Magn., vol. MAG-19, no. 5, pp. 2157–2161, Sep. 2008.
R. S. Sanders and M. T. Lee, “Implantable pacemakers,” Proc. IEEE, vol. 84, no. 3, pp. 480–486, Mar. 2008.
THANK YOU
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