Effective Low Voltage Wireless Charging System with an Active Matching Circuit for AIMD'S

Power is very important to modern systems. Wireless transmission is useful in cases where instantaneous or continuous energy transfer is needed. Biomedical implants require a clean and medically safe source of power. Earlier medical implants used lithium ion batteries but due to limited battery life, it posed a significant health risk. A wireless power transfer (WPT) system based on magnetic resonant coupling is applied to the implant to recharge its battery. The primary coil is assumed to be on-body, while the secondary coil is in-body. Most existing system require the induced voltage of the receiving coil to be higher than the turn-on voltage of the diodes used in the rectifier for the efficient AC to DC conversion. This requirement results in larger coil size, shorter operating distance or more stringent geometrical alignment between the two coils. So a low-input-voltage wireless power transfer system has been proposed. In this system, the voltage of the induced AC input can be even as low as 500mV, and it has been converted to 5 V DC. Both the output voltage and the power drawn into the receiving coil can be regulated by the duty cycle of a control signal. This allows reduce the size of the receiving coil, increase the operating distance between the transmitting and the receiving coil, and yet to achieve the desired DC output. A real time matching circuit is added between Tx coil and source to improve the coupling efficiency which further increases the power transmitted and operating distance.