Constant output voltage and non-communication-based maximum efficiency tracking for wireless power transfer systems: Single current control of primary-side

Wireless power transfer (WPT) technology is a novel power transmission technology using electromagnetic field as the transmission medium. It uses the advantages of electromagnetic coupling in the near field to realize contactless transmission of electric energy on the basis of resonance theory. This mode has the advantages of stability, flexibility, efficiency and safety. WPT is mainly used for non-contact charging of electrical equipment without electrical connection. It can safely, flexibly and quickly charge the electrical equipment, which makes up for the shortcomings of the traditional charging mode. Due to the change of the load or the transmission coil position in WPT system, the transmission efficiency will drop sharply. It is of great significance to maintain the maximum efficiency transmission. This paper proposes a novel maximum efficiency transmission method. This method can achieve the maximum efficiency transmission with constant voltage output by controlling the primary-side current without communication feedback between the primary-side and the-secondary side. The Buck-Boost converter with constant output voltage is introduced at the load-side to equivalent the actual load. By adjusting the duty ratio of the Buck converter on the primary side and detecting the minimum input current, the maximum transmission efficiency could be tracked. The theoretical conditions of the method are analyzed and experimental verification is performed. The experimental results of variable relative position load show that the transmission efficiency of the proposed method can still reach 83%.