Wireless charger

Sammanfattning: This project focuses on wireless power transmission (WPT). More specifically, the use of inductive coupling with resonance. The resonance phenomenon makes the transfer of power more efficient, through matching the inductive and capacitive reactances thus eliminating the reactive losses. A wireless smartphone charger has been built with this method for demonstration, and some tests were performed. The charger consisted of a primary “transmitting circuit” and a secondary “receiving circuit”. The built charger did not achieve full resonance, but it achieved longer wireless transmission distance compared to that of a commercial wireless phone charger. The first experiment confirmed the DC/AC characteristics of the transmitting circuit, and the ability for the voltage to oscillate at a higher level than the input voltage. The voltage oscillated at 45kHz. The second experiment confirmed the AC/DC characteristics of the receiving circuit, and the ability to regulate the voltage to a constant 5V. The minimum required input voltage for the receiving circuit, to achieve a constant 5V output, was approximately 6V. Frequencies from 100Hz to 350kHz were tested and it had no severe impact on stability of the output voltage. The third and last test used both circuits, and showed the relationship between input voltage and transmission distance. The maximum distance achieved for the complete device was ~4.3cm at an input voltage of ~20V. When having the coils touch (Transmission distance ~0cm), the minimum required voltage was 6.6V, whereas a commercial wireless charger needs 5V.