Arturo Mediano

Design of Class E Amplifier With Nonlinear and Linear Shunt Capacitances for Any Duty Cycle

One of the main advantages of class E amplifiers for RF and microwave applications relies on the inclusion of a shunt capacitance in the tuned output network. At high frequencies, this capacitance is mainly provided by the output parasitic capacitance of the device with perhaps a linear external one for fine adjustments. The devices output capacitance is nonlinear and this influences the design parameters, frequency limit of operation, and performance of the class E amplifier. This paper presents a design method for the class E amplifier with shunt capacitance combining a nonlinear and linear one for any duty cycle, any capacitances nonlinear dependence parameters, and any loaded quality factor of the tuned network. Nonlinear design with possibly different duty cycles is of relevance to maximize power or, alternatively, frequency utilization of a given device. Experimental, simulated, and compared results are presented to prove this design procedure

High-Efficiency Broadband Parallel-Circuit Class E RF Power Amplifier With Reactance-Compensation Technique

Class E amplifier offers high efficiency approaching 100% for an ideal case. This paper introduces a first practical implementation of a novel broadband class E power amplifier design combining a parallel-circuit load network with a reactance compensation technique. The novel broadband parallel-circuit class E load network using reactance compensation technique has been discussed based on theory and its experimental verification. A proper guidelines method of designing a high-efficiency broadband class E power amplifier with an LDMOS transistor until the final prototype measurement and optimization will be discussed. In the measurement level, the drain efficiency of 74% at an operating power of 8 W and power flatness of 0.7 dB are achieved across a bandwidth of 136-174 MHz. The efficiency result is the highest result for VHF broadband frequency to date with a low supply voltage of 7.2 V. Simulations of the efficiency, output power, drain voltage waveform, and load angle (impedance) were verified by measurements and good agreements were obtained.

Class-D/DE Dual-Mode-Operation Resonant Converter for Improved-Efficiency Domestic Induction Heating System

Induction heating (IH) technology is nowadays widely present in domestic appliances because of its cleanness, high efficiency, and faster heating process. All of these advantages are due to its heating process, where the pot is directly heated by the induced currents generated with a varying magnetic field. As a result, the glass where the pot is supported is not directly heated and, consequently, efficiency and heating times are improved. IH systems are based on dc-link inverters to generate the required alternating current to feed the inductor. Usually, resonant converters are used to achieve higher efficiencies and power densities. In such systems, the maximum output power and efficiency are achieved at the resonant frequency, and the switching frequency is increased to reduce the output power. As a consequence, in these converters, the efficiency is also reduced in the low-medium output power range. This paper proposes the use of the half-bridge inverter in two operating modes to achieve higher efficiency in a wide output power range. The power converter topology can be reconfigured by changing the resonant capacitors through electromechanical relays. As a consequence, the entire efficiency of the cooking process is improved with a cost-effective procedure.

High Efficiency AC–AC Power Electronic Converter Applied to Domestic Induction Heating

This paper presents the analysis and design of a new ac-ac resonant converter applied to domestic induction heating. The proposed topology, based on the half-bridge series resonant inverter, uses only two diodes to rectify the mains voltage. The proposed converter can operate with zero-voltage switching during both switch-on and switch-off transitions. Moreover, this topology doubles the output voltage, and therefore, the current in the load is reduced for the same output power. As a consequence, the converter efficiency is significantly improved. The analytical and simulation results have been verified by means of a 3600-W induction heating prototype. An efficiency study has been carried out, obtaining values higher than 96%.

Accurate measurement of the specific absorption rate using a suitable adiabatic magnetothermal setup

Accurate measurements of the specific absorption rate (SAR) of solids and fluids were obtained by a calorimetric method, using a special-purpose setup working under adiabatic conditions. Unlike in current nonadiabatic setups, the weak heat exchange with the surroundings allowed a straightforward determination of temperature increments, avoiding the usual initial-time approximations. The measurements performed on a commercial magnetite aqueous ferrofluid revealed a good reproducibility (4%). Also, the measurements on a copper sample allowed comparison between experimental and theoretical values: adiabatic conditions gave SAR values only 3% higher than the theoretical ones, while the typical nonadiabatic method underestimated SAR by 21%.

Design and Implementation of a High-Efficiency Multiple-Output Resonant Converter for Induction Heating Applications Featuring Wide Bandgap Devices

Efficiency is a key design parameter when designing the power converters for domestic induction heating applications, since it determines not only the environmental impact of the power converter but also its final performance and reliability. In this paper, the design of high-efficiency converters for induction heating applications is discussed, focusing on the advantages of using wide bandgap devices. As a conclusion, a multiple-output boost resonant ac-ac converter is proposed, significantly improving current state-of-the-art efficiency and achieving a reduced component-count solution for multiple-load systems. The proposed converter has been tested through a dual-output boost resonant inverter for domestic induction heating applications. The design procedure is detailed, including the design of an optimized gate drive circuit for this application. Experimental results show significant improvements in efficiency in the whole operating range, and an accurate output power control, proving the benefits and feasibility of the proposed SiC-based converter.

Modulation Scheme for Improved Operation of an RB-IGBT-Based Resonant Inverter Applied to Domestic Induction Heating

Domestic induction appliances require power converters that feature high efficiency and accurate power control in a wide range of operating conditions. To achieve this modulation techniques play a key role to optimize the power converter operation. In this paper, a series resonant inverter featuring reverse-blocking insulated gate bipolar transistors and an optimized modulation technique are proposed. An analytical study of the converter operation is performed, and the main simulation results are shown. The proposed topology reduces both conduction and switching losses, increasing significantly the power converter efficiency. Moreover, the proposed modulation technique achieves linear output power control, improving the final appliance performance. The results derived from this analysis are tested by means of an experimental prototype, verifying the feasibility of the proposed converter and modulation technique.

Direct AC–AC Resonant Boost Converter for Efficient Domestic Induction Heating Applications

Domestic induction heating (IH) is currently the technology of choice in modern domestic applications due to its advantages regarding fast heating time, efficiency, and improved control. New design trends pursue the implementation of new cost-effective topologies with higher efficiency levels. In order to achieve this aim, a direct ac-ac boost resonant converter is proposed in this paper. The main features of this proposal are the improved efficiency, reduced component count, and proper output power control. A detailed analytical model leading to closed-form expressions of the main magnitudes is presented, and a converter design procedure is proposed. In addition, an experimental prototype has been designed and built to prove the expected converter performance and the accurateness of the analytical model. The experimental results are in good agreement with the analytical ones and prove the feasibility of the proposed converter for the IH application.

Efficient and Cost-Effective ZCS Direct AC–AC Resonant Converter for Induction Heating

Domestic induction-heating technology requires specific features such as high output power levels in a reduced enclosure, elevated operating temperature, large load variation, and reduced cost. To fulfill these requirements, classical solutions are based on the combination of a rectifier and a dc-link inverter. This is a well-balanced solution, but there is still room for efficiency and cost improvements. Unlike previous proposals, this paper proposes a direct ac-ac converter to reduce the component count, reduce cost, improve reliability, and increase efficiency. The proposed converter is a voltage-source series-resonant converter that achieves linear output power control, reducing control complexity. Moreover, the proposed converter achieves soft switching during both turn-on and turn-off transitions, further improving the efficiency and enabling the selection of low-speed devices with improved conduction properties. A 3.6-kW converter has been designed and implemented, verifying the feasibility of the proposal and the expected performance.

A Class-E Direct AC–AC Converter With Multicycle Modulation for Induction Heating Systems

Induction heating systems are the technology of choice in many industrial, domestic, and medical applications due to its high performance. The core component of such systems is the power supply, which is usually composed of a rectifier stage and a resonant inverter. In order to simplify and further optimize the performance of the power supply, a class-E direct ac-ac converter featuring multicycle modulations is proposed in this paper. The proposed converter is composed of two switching devices that enable the direct ac-ac conversion. Single- and multicycle operation modes have been analytically described to prove the benefits, in terms of peak voltage reduction and output power control capabilities. A prototype featuring SiC junction-gate field-effect transistor devices, which perfectly fit these applications, has been designed and built to prove the feasibility of the proposed converter. The experimental results match the analytical results and validate the benefits of this converter.