An Improved Control Method of a Resonant-Inductive Wireless Charger with Input Power Factor Correction

Conventional wireless charging systems are often connected through power factor corrector (PFC) with a passive input electromagnetic interference (EMI) filter to AC grid. However, input EMI filters are bulky and relatively expensive. In order to reduce the size and cost of EMI filters, the spread spectrum technique based on switching frequency modulation is used. Despite the fact that the technique can reduce peak EMI levels by more than 10 dB, it has disadvantages, such as considerably increased total harmonic distortion (THD) of PFC input current, decreased power factor and increased peak current of a pulse transformer. In order to reduce significantly or even eliminate the disadvantages of the classical switching frequency modulation, an improved control method of the power-factor-corrected wireless charging system is proposed and verified using simulations in PSIM software. The method is based on the hybrid (duty cycle and frequency) modulation of PFC control signal to reduce EMI without deteriorating input current THD and low-frequency components, and power factor.