Design for continuous‐current‐mode operation of inductive‐power‐transfer converters with load‐independent output

Abstract

The control design of inductive power transfer (IPT) converters can be greatly simplified by exploring the property of load-independent output. However, IPT converters can easily enter a discontinuous current mode (DCM) operation due to the non-linearity of the output diode rectification circuit at some loading conditions. The switching between operations of continuous current mode (CCM) and DCM within a switching cycle is highly non-linear, making the converter behaviour difficult to predict and analyse. The well-known first harmonic approximation (FHA) analysis method and the load-independent output property are no longer applicable when the converter enters DCM operation. This paper presents a simple and yet effective harmonic analysis method to reveal the main reason for the converter to enter DCM operation. Subsequently, the load boundary between CCM and DCM operations is derived in detail as a design criterion. A solution by increasing the input impedances at some higher order harmonic frequencies is also suggested to extend the load range against DCM operation. Finally, IPT prototypes using two higher order compensation circuits, having load-independent voltage output and capacitor filter, are demonstrated to verify the theoretical analysis.

Efficiency optimization for LCC‐LC compensated inductive coupling power transfer system with load‐independent zero‐phase‐angle and constant voltage output

“…With the known region D, the efficiency optimization of the ICPT system can be executed by finding the optimal secondary-side compensation parameters. Furthermore, the primary-side compensation parameters can be calculated using (9). In order to demonstrate the proposed efficiency optimization method of the LCC-LC compensated ICPT system.…”

“…8 Moreover, when the capacitor filter is utilized, the secondary-side coil current with abundant harmonic may be discontinuous when the load resistance increases to a specific value. 9 Although the secondary-side coil current can enter continuous mode by reconstructing the compensation capacitor with an inductor-capacitor series network with higher harmonic impedance, 9 current distortion is still visible. In addition, one LC series filter network resonating at switching frequency is connected in the ICPT system to attenuate current harmonics in the primary-side coil, 10 which introduces more passive components.…”

Fault Tolerant Modular Inductive Power Transfer System Design Using Resonator Coil

“…The induced emf on the resonator due to the Rx side becomes zero, and the intrinsic resistance of the resonator coil acts as the load. Assuming that the system operates near resonance frequency, the reflected impedance on the Tx side can be written as in (14).…”

“…In this study, the design methodology based on fundamental harmonic approximation (FHA) is presented under these assumptions: No-higher order harmonics and continuous coil current, also known as continuous current mode (CCM) [13]. However, an IPT system can also operate in discontinuous current mode (DCM) because of the diode rectifiers and load conditions [14]. In DCM, the current of the coils have odd harmonics (3 rd , 5 th ), which are comparable to fundamental component.…”

Novel method to operation conditions identification of high-order power converters

“…However, it is difficult to build mathematical models for HOPCs. To deal with this issue, a harmonic analysis method was proposed to identify the criteria of different loading conditions to operate at DCMs [31] . However, it bears great inaccuracies and the stability near the switching frequency is unpredicted by time-domain methods.…”