Multiple Receiver Wireless Power Charger for Mobile Electronic Devices in Near Field
Portable consumer electronics like mobile phones, laptops, tablets and other devices have flooded the markets these days. While providing the convenience of keeping in touch with friends and family at the touch of a button, or performing complex scientific computations of a physical system, these devices have become an essential part of everyone’s day-to-day lives. In order to keep them up and running at all times, they need electrical energy, which in most cases is stored in the batteries of these devices. These batteries have limited storage capacity and lifetime. For these reasons, portable device users have to carry wired chargers all the time which can be an inconvenience and limits accessibility. Hence, there is a need for an alternative method of charging these devices. Wireless power transfer provides a viable solution to the challenges encountered by portable device consumers when using the traditional method of charging batteries. This thesis presents a multiple receiver wireless power transfer system for charging mobile phone batteries. The circuit consists of a transmitter and two receiver systems. A mathematical analysis of the circuit is carried out and simulated to understand its behavior with variation in coupling coefficient and load. In order to charge the mobile phones without an extra communication module over a wide range of coupling coefficients, a variable frequency control algorithm is used. The transmitter circuit uses the algorithm to track the maximum input power of the system. The output voltage of the receiver circuit is controlled to meet the power requirement of the load as coupling coefficient varies by using a switch capacitor modeled as two back to back connected MOSFETs with their drain-to-source capacitance. The proposed converter circuit topology is simulated and the results are presented. The circuit operates over a wide range of coupling coefficient, with good voltage regulation. Zero voltage switching (ZVS) is achieved at the inverter switches and the power requirement of the mobile phones are met without use of an extra communication module. The resonance frequency of the circuit is 5.7MHZ and it is design to deliver 10W (5V, 2A) each to two mobile phones.