Design Of Smart Wireless Charger Based On DSC

The wireless charging technology is of convenience, compatibility and safety, and hasa number of applications in some special occasions，which give it a great space to developnow. However, it is the low power transfer efficiency that restricts the development andwide use of wireless charging. The power transfer rules and communication contractbetween wireless charger (TX) and wireless power receiver (RX) are defined in Qi Spec.TX can adjust transferred power according to various load so that the efficiency of thesystem is higher. MC56F82743is general digital signal controller (DSC) produced byFreescale Semiconductor recently, which is of high cost-performance ratio. A smartwireless charger, using MC56F82743, based on magnetic induction and compatible withQi Spec, which is an reference design participated by the authour during internship inFreescale, is designed in this paper. This wireless charger can work with RX which alsocomplies with Qi Spec to transfer power with high efficiency. And the TX is of some smartfeatures such as over voltage protection, over current protection, low power consumptionmode through object sensing circuit and foreign object dectecting (FOD).Firstly, the principle of wireless charging is analyzed in detail, including the structureof the wireless charging system, impedance matching, PFM control. The wireless chargingsystem is simulated in Saber. It is convenient and simple to analysis the working ofwireless charging system with different parameters, also provide references to acual systemdesign.After analysis and simulation of wireless charging system, this paper gives a design ofa smart wireless charger with the ablity to output5W power, which is compitible with Qispec. This description of hardware design includes of the Digital Signal ControllerMC56F82743and the peripheral circuits, sensing circuit, LC resonant circuit, full bridgeinverter circuit, demodulating circuit and object sensing circuit. And the software design ispresented in detail in this paper, including the key code of some peripheral setting, programflow chart, the PFM+PWM power control algorithm, low power mode and foreign objectdectection method.At last, a actual wireless charger designed in this paper is used to do experiences with RX compatible with Qi spec. And some signals under various loads as well as the efficencyof the system can be get through testing. It is demonstrated that the wireless chargerdesigned in this paper can charge the RX with load of0-5W and the functions of protection,low power mode and foreign object detection can work.