Maximum power transfer considering limited available input power in ultrasonic wireless power transfer for implanted medical devices

Ultrasonic energy harvesting emerges as a leading candidate for clean energy used in implanted medical devices. In implanted medical applications, in order to prevent hot spots, only very low input voltage is allowed, while a high enough output voltage is needed for battery charging. Recent studies use an inductor in either series or parallel to the piezoelectric transducer to boost up output rectifier voltage, sometimes with the price of failing to achieve maximum power transfer. This study provides a method to obtain both maximum power transfer and highly boosted rectifier output voltage for ultrasonic wireless power transfer, considering the limited available input power case, to get enough high output voltage for battery charging in implanted medical applications.