Design Guidelines to Allow Bifurcation Operation of Wireless Battery Charger with Primary Side Controller

In wireless power transfer (WPT) system for battery charger, the mutual inductance is mainly influenced to the secondary voltage, current, and power. These variables cannot be directly measured from the primary without the additional wireless sensors. This paper presents the design guidelines to achieve the coupling independent operation compatible with wireless battery charger. The current gain is independent from mutual inductance and depended only on the ratio of two coil inductances. Thus, the secondary current can be estimated by the primary current. The charging current and battery voltage are also controlled by the primary side controller. Finally, the experimental results show that the charging current is equal to the primary current with efficiency of 80%.