The simplest rectifier topology tolerant of load resistance variation and circuit analysis by square-wave approximation

We propose a novel, extremely simple rectifier whose input impedance is insensitive to the variation of the load resistance. Thanks to this insensitivity, the reflection loss caused by the load variation is minimized, and thus the rectifier keeps high efficiency in a wide load range. This characteristic is welcomed by wireless power transfer, especially for variable or unstable load resistance. The wide-load-range characteristic is demonstrated by time domain analysis with a new approximation technique. By employing a square-wave-stimulus approximation, we find that the rectifier has two conduction modes and autonomously selects a preferable mode depending on the load resistance. Under a light load condition, the rectifier works like a single series rectifier and the input impedance is proportional to the load resistance. Under a heavy load condition, the rectifier works in a peculiar manner unlike any other rectifiers, and the input impedance is inversely proportional to the load resistance. The condition of the light and heavy load is also clearly formulated by the analysis. The comparison with the simulation result shows that the approximated analysis reflects the rectifier's behavior well, and so the result is useful for the analysis and the design of the proposed rectifier.