Modeling and Analysis of Class EF and Class E/F Inverters With Series-Tuned Resonant Networks

Aldhaher, Samer; Yates, David C.; Mitcheson, Paul D.

doi:10.1109/tpel.2015.2460997

Cited by 99 publications

(76 citation statements)

References 17 publications

(28 reference statements)

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“…Comparing with the Class D inverter or full-bridge Class D inverter, the Class EF 2 inverter can be designed to achieve ZVS and ZVDS, which makes the single switch operate efficiently up to the megahertz range [49]. Other two benefits of this topology are that the switch's drain voltage and the output current do not contain a second harmonic component, and has an improved electromagnetic interference performance.…”

Section: Class Ef N Resonant Invertermentioning

confidence: 99%

An Overview of Resonant Circuits for Wireless Power Transfer

et al. 2017

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Abstract:With ever-increasing concerns for the safety and convenience of the power supply, there is a fast growing interest in wireless power transfer (WPT) for industrial devices, consumer electronics, and electric vehicles (EVs). As the resonant circuit is one of the cores of both the near-field and far-field WPT systems, it is a pressing need for researchers to develop a high-efficiency high-frequency resonant circuit, especially for the mid-range near-field WPT system. In this paper, an overview of resonant circuits for the near-field WPT system is presented, with emphasis on the non-resonant converters with a resonant tank and resonant inverters with a resonant tank as well as compensation networks and selective resonant circuits. Moreover, some key issues including the zero-voltage switching, zero-voltage derivative switching and total harmonic distortion are addressed. With the increasing usage of wireless charging for EVs, bidirectional resonant inverters for WPT based vehicle-to-grid systems are elaborated.

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Section: Class Ef N Resonant Invertermentioning

confidence: 99%

An Overview of Resonant Circuits for Wireless Power Transfer

et al. 2017

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“…It is assumed that switch is on for the period 0 ≤ ωt < 2πD and off for the period 2πD ≤ ωt < 2π. In [6] a detailed analysis was performed on Class EF inverters and the general form of the equations that describe the voltages and currents of the inverter were derived. Here, we will only present the final form of the equations that will be used to specify the conditions for load-independence operation.…”

Section: A General Modelmentioning

confidence: 99%

“…Effect of Load Variation Fig. 2 shows the effect of the load resistance varying by 25 % above and below the optimum load for a Class EF 2 inverter [6]. It can be noticed that ZVS is lost once the load varies above or below its optimum value.…”

Section: A General Modelmentioning

confidence: 99%

Load-independent Class EF inverters for inductive wireless power transfer

Aldhaher

Mitcheson

Yates

2016

2016 IEEE Wireless Power Transfer Conference (WPTC)

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Abstract-This paper will present the modelling, analysis and design of a load-independent Class EF inverter. This inverter is able to maintain zero-voltage switching (ZVS) operation and produce a constant output current for any load value without the need for tuning or replacement of components. The loadindependent feature of this inverter is beneficial when used as the primary coil driver in multi-megahertz high power inductive wireless power transfer (WPT) applications where the distance between the coils and the load are variable. The work here begins with the traditional load-dependent Class EF topology for inversion and then specifies the criteria that are required to be met in order achieve load-independence. The design and development of a 240 W load-independent Class EF inverter to drive the primary coil of a 6.78 MHz WPT system will be discussed and experimental results will be presented to show the load-independence feature when the distance between the coils of the WPT system changes. A. IntroductionResonant soft-switching converters, such as Class E and Class EF 2 inverters, are commonly used in high power inductive WPT systems that operate at multi-megahertz frequencies due to their efficient operation and simple construction [1], [2]. However, they are only designed to operate at optimum switching conditions for a fixed load and therefore are highly dependent on the load value. They are less tolerant to load variations compared to other inverters, such as Class D inverters, which causes them to become less efficient as the load deviates from its optimum value. Consequently, this limits the WPT system to function efficiently only at a fixed coil separation distance and for a narrow load range.There have been attempts to tune the Class E inverter while in operation to compensate for any variations in the load by using saturable reactors and varactors [3]. While these methods can increase the load range that Class E inverter can tolerate, they require either the user to tune them manually by observing the MOSFET's drain waveform or require a control loop to be implemented. Additionally, the tuning elements can limit the Class E inverter to operate at higher power levels.It was shown in [4], [5] that the Class E and Class φ 2 inverters when used with a finite-DC inductor instead of the usual choke, can be designed such that the they achieve zerovoltage switching (ZVS) and produce a constant output voltage as the load resistance varies. These designs extends the load range at which the Class E and Class φ 2 inverters can operate efficiently from infinite load resistance (open circuit) to a certain minimum load resistance. Although these designs can be Fig. 1. The Class EF inverter applied to several applications, such as high frequency DC/DC converters, they cannot be applied efficiently in inductive WPT application where the distance between the coils changes. This is because the load will range from zero resistance (short circuit) when the coils are completely separated from each other to a certain ma...

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“…With the harmonic-tuned circuit connected in series to the load network, it is designed to have high impedance to odd harmonics, and thus its switch-voltage waveform is shaped to a near-square wave. Similarly, in the class EF2 [20], [21], the class Ф2 [22], [23], and the class Ф2-derived boost converter [24], the series LC circuit tuned to the second-harmonic frequency is connected in parallel with the switch. The switch-voltage waveforms are similar to the trapezoidal wave primarily containing odd harmonics, and the This article has been accepted for publication in a future issue of this journal, but has not been fully edited.…”

Section: Introductionmentioning

confidence: 99%

A Family of High-Frequency Single-Switch DC–DC Converters With Low Switch Voltage Stress Based on Impedance Networks

Lee

Chung

Han

et al. 2017

IEEE Trans. Power Electron.

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This paper presents a novel family of single-switch resonant dc-dc converters with low switch voltage stress. The single-switch resonant converter which has a ground-referenced switch is advantageous for implementing the gate drive circuit and operating at several-MHz switching frequency. However, the conventional ones mostly have high voltage stress on the switch, roughly 4-5 times the input voltage. In this paper, we propose the single-switch converter topologies derived from the drain-source impedance networks consisting of two inductors and two capacitors. The switch voltage of the proposed converters is shaped into a near trapezoid by designing the resonant networks to have the desired drain-source impedance. Furthermore, a simple and specific design scheme is presented here so that the peak switch voltage is lowered to 2.2-2.5 times the input voltage while zero voltage switching (ZVS) is achieved. Experimental results from a 20-W GaN-based prototype operating at 10 MHz demonstrate the feasibility of the proposed converter topologies and the design method.Index Terms-High frequency, resonant converter, single switch, switch peak voltage, zero voltage switching (ZVS).

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Modeling and Analysis of Class EF and Class E/F Inverters With Series-Tuned Resonant Networks

Cited by 99 publications

References 17 publications

An Overview of Resonant Circuits for Wireless Power Transfer

An Overview of Resonant Circuits for Wireless Power Transfer

Load-independent Class EF inverters for inductive wireless power transfer

A Family of High-Frequency Single-Switch DC–DC Converters With Low Switch Voltage Stress Based on Impedance Networks

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