Class-E Half-Wave Zero dv/dt Rectifiers for Inductive Power Transfer

Abstract

This paper analyses and compares candidate zero dv/dt half-wave Class-E rectifier topologies for integration into multi-MHz inductive power transfer (IPT) systems. Furthermore, a hybrid Class-E topology comprising advantageous properties from all existing Class-E half-wave zero dv/dt rectifiers is analysed for the first time. From the analysis, it is shown that the hybrid Class-E rectifier provides an extra degree of design freedom which enables optimal IPT operation over a wider range of operating conditions. Furthermore, it is shown that by designing both the hybrid and the current driven rectifiers to operate below resonance provides a low deviation input reactance and inherent output voltage regulation with duty cycle allowing efficient IPT operation over wider dc load range than would otherwise be achieved. A set of case studies demonstrated the following performances: 1) For a constant dc load resistance, a receiving end efficiency of 95 % was achieved when utilising the hybrid rectifier, with a tolerance in required input resistance of 2.4 % over the tested output power range (50 to 200 W). 2) For a variable dc load in the range of 100 % to 10 %, the hybrid and current driven rectifiers presented an input reactance deviation less than 2 % of the impedance of the magnetising inductance of the inductive link respectively and receiving end efficiencies greater than 90 %. 3) For a constant current in the receiving coil, both the hybrid and the current driven rectifier achieve inherent output voltage regulation in the order of 3 % and 8 % of the nominal value respectively, for a variable dc load range from 100 % to 10 %.

Multi-MHz IPT Systems for Variable Coupling

“…The inherent regulation properties of resonant converters can sometimes be used to maintain soft switching, for instance, non-synchronous Class E rectifiers inherently change the duty cycle of the diode when the dc-load changes, and consequently achieve ZVS. Furthermore, in [21] a hybrid Class E rectifier (a Class E rectifier with an additional capacitance that provides an additional degree of design freedom) not only achieves ZVS, but also can be designed to inherently regulate the output voltage as the load changes. The inherent regulation properties of resonant converters have been utilised for multiple purposes, for example in [22] the resonant nature of a LCC converter was utilised for power factor correction, and in [23] an inherent over-current protection feature was implemented by placing an auxiliary circuit in parallel with the resonant capacitor of a LLC resonant converter which shorts the capacitor and detunes the resonant tank when a fault shorts out the load.…”

Analysis and design of generalized class-E rectifier

“…Resonant rectifiers have important roles in many applications such as wireless power transfer (WPT) systems [1][2][3][4][5][6][7], rectifier part of the resonant DC-DC converters [8][9][10][11][12][13][14][15][16], and energy harvesting circuits [17]. The resonant rectifiers are suitable for high-frequency and high-efficiency operations due to the soft switching [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]17]. For designs of the resonant rectifier, it is important and helpful to comprehend typical characteristics, for example, AC-to-DC transfer function, peak voltage across the rectifier diode, and power output capability.…”

Load-Independent Class E/EF Inverters and Rectifiers for MHz-Switching Applications

“…The receiving coil was formed by copper plating the propeller guard of the drone forming a single-turn 330-nH coil. The rectifier on-board the drone was a hybrid Class E rectifier introduced in [26]. Thermal imaging showed that when the drone was at its furthest point away from the transmitting coil, the diodes were contributing to the majority of the losses in the rectifier, since the rectifier operates at a low-voltage high-current regime.…”