Mechanism Analysis and Elimination of Multiple Pulse Phenomenon of Active Rectifier in Wireless Power Transfer Systems

Active rectifier is widely used in wireless power transfer systems. On/off delay-compensation technique is commonly used to improve the power conversion efficiency (PCE) of rectifier. However, it also introduces multiple pulse (MP) problem, which could greatly reduce the efficiency and significantly impacts the reliability of system. In this work, the mechanism of MP is comprehensively analyzed and two elimination methods are indicated and compared. The critical circuit parameter is analyzed. To implement the method, an active rectifier with dual-edge D-latch (DEDL) is proposed. The advantage of the DEDL is that the output of comparator can be latched up to achieve an adjustable delay time at both rising and falling edges. As the result, the MP at the output of the comparator will not affect the gate of the power metal oxide semiconductor field effect transistor. The rectifier is fabricated with a standard 0.18 μm complementary metal oxide semiconductor process. The core area of chip is 0.268 mm2. The maximum output power of rectifier is 40 mW. The PCE is higher than 90% when Vac = 2 V and 51 Ω<RL<300 Ω. The peak PCE is 93.3% when Vac = 2 V and RL = 100 Ω. Measurement results show the effectiveness of the proposed elimination method, and also prove that the theoretical analysis of MP is correct.