## 1 Introduction  
Wireless power transfer (WPT) systems are widely applied in various applications such as electric vehicles (EVs), mobile phones, unmanned aerial vehicles, and robots [1; 2; 3; 4; 5; 6; 7; 8]. These systems overcome the technical limitations of battery capacities and offer an easier charging alternative to plug-in charging methods during unmanned and autonomous mobility, thereby eliminating the possibility of hazards such as electric shock and leakage from cracked and worn-out cables [9; 10]. WPT systems employ inductive power transfer (IPT) and magnetic resonance methods. Most of the WPT devices adopt the IPT charging method owing to its high efficiency. Major studies related to WPT based on IPT have focused on the pad design and the compensation topology of the IPT converter. In terms of pad design, the studies mainly focused on overcoming the low coupling coefficients of existing circular and rectangular pads. The pad designs with polarity proposed in recent studies offer a higher coupling coefficient k and better consistency in alignment than basic pads [11; 12; 13; 14; 15]. Compensation topologies have been proposed to resolve the phase shift caused by the coil inductance of the charging pad. The phase difference between the voltage and current increases the current flowing through the IPT system owing to the increase in circulating current and reactive power, which leads to additional system losses. Various compensation topologies have been presented and analyzed. These topologies are classified into four basic resonant topologies, i.e., the series-series (SS), series-parallel (SP), parallel-series (PS), and parallel-parallel (PP). Furthermore, certain high-order topologies have been proposed to improve the compensation characteristics [16; 17; 18; 19; 20]. Compensation topologiesare significant parameters that can improve efficiency by minimizing the volt-ampere (VA) ratings. It further influences the constant output characteristics (current or voltage), which are determined by the constant current (CC) or constant voltage (CV) compensation topology structure. Most IPT systems have either CV or CC output characteristics; thus, the output characteristics can cause overcurrent or overvoltage when charging the battery through the IPT system, which can damage the battery [21; 22]. Moreover, when WPT is applied to an automated system, it is difficult to respond immediately to prevent secondary damage in the event of a battery accident. To prevent these problems, most batteries include a battery management system (BMS), which has an internal monitoring function and a control-charging mode. When the state of charge (SoC) is low, the BMS can be in CC mode to avoid overcurrent, and when SoC is high, the BMS changes the CC mode to CV mode to avoid overvoltage. However, applying BMS and telecommunication functions inevitably increases the system's cost and weight. Thus, it is not suitable for low-cost and low-volume mobility systems such as drones, mobile phones, wireless earphones, and electric bikes. To reduce the cost of controllers in low-cost models, researchers have proposed various safety strategies. It was proposed in [23] that a slot current protection circuit, such as ZnO resistance, be included or a signal from the control sensor be sent to the metal-oxide semiconductor field-effect transistor (MOSFET) switch to protect against faults. However, this mechanism offers protection only in the case of a fault, and a BMS is still required, which increases the cost owing to specific components. Meanwhile, in [24; 25], a CC/CV solution via topological access was proposed; in [24], a circuit that adds a coil in the primary pad to achieve the CC/CV mode was proposed, while in [25], a topology based on a high-order compensation topology was proposed. In [26; 27; 28; 29; 30], a hybrid topology was proposed to achieve the CC/CV mode by using a switching capacitor. In [26; 27], CC/CV control by switching a capacitor between the two topologies was proposed.