J.M. Burdio

Domestic Induction Appliances

In this paper several research topics pertaining to the design and modeling of domestic induction appliances are reviewed. Each topic is summarized, stressing its most significant advances and pointing to its future tendencies. A bibliographic review showing some of the published papers during the last years is included. The emphases and relative contributions of some of them are also discussed.

Improved Performance of Half-Bridge Series Resonant Inverter for Induction Heating with Discontinuous Mode Control

In this paper, a study of the Discontinuous current Mode (DM) control applied to a half-bridge series resonant inverter for domestic induction heating is presented. The proposed control is interesting for this application because it exhibits reduced switching losses and the output power control is linear with the switching frequency. Considering that the load is disconnected from the source during part of the switching period, with DM control. A time-domain analysis method is proposed to obtain the analytical expression of the output power, the capacitor voltage and load current. The validity of the analytical expression is checked through simulation. Finally, an experimental comparison of efficiency between traditional controls and the DM control is performed for the induction heating application. In the low power range the efficiency of DM control is higher than traditional schemes.

Frequency-dependent resistance in Litz-wire planar windings for all-metal domestic induction heating appliances

In this paper the frequency-dependent resistance in Litz-wires planar windings for all-metal domestic induction heating appliances is analyzed. For planar inductors, where size is not an essential constraint, an analytical model is developed based on the superposition of different loss effects in the wire, several inductors were constructed and results with both nonloaded and loaded inductors are compared with theoretical predictions

Series resonant multi-inverter with discontinuous-mode control for improved light-load operation

Operation under light-load conditions is a general issue when developing power converters, as it can lead to system instability and/or decreased performance. This topic is especially important for resonant converters, as the efficiency significantly degrades when the operation point is set out of the resonant conditions. Considering the importance of efficiency for the power converter reliability, the environmental impact, and the regulation concerns, a major effort to improve the operation under light-load conditions is justified. Domestic induction heating is an application example where the variable load and the output power requirements imply the operation under a wide range of conditions, including long-term light-load operation. The aim of this paper is to propose an improved control scheme for the series resonant multi-inverter, a cost-effective topology to supply multiple inductive loads, based on the discontinuous-mode operation. Two different control strategies are proposed: regenerative control (RC) and direct conduction control (DCC). An analytical study is performed and the main simulation results are presented. Besides, an experimental series resonant multi-inverter prototype is used to validate the simulation results.

Real-time FPGA-based Hardware-in-the-Loop development test-bench for multiple output power converters

The implementation of multiple-inductor power converters requires often the development of specific purpose control architectures to obtain the most of the converter. These are usually based on a processor, which provides software flexibility, and specific purpose hardware, which provides customized functionalities. In addition, recent trends suggest the integration of both functionalities in a single chip using an embedded processor and customized hardware, providing a System-on-Programmable-Chip (SoPC) solution. The aim of this paper is to implement a SoPC system which provides flexibility and customized hardware, and develop a real-time FPGA-based development test-bench based on the Hardware-In-the-Loop (HIL) simulation technique, which accelerates simulation, reduces design cycle times, and allows software and power converter modulation schemes development. The complete system is integrated by a multiple-inductor power converter and an FPGA, which contains a MicroBlaze embedded processor and a specific purpose Digital Pulse Width Modulator (DPWM). HIL at power level is applied by implementing the power converter model into the FPGA. It has been designed with the VHDL-2008 float_pkg package, which allows a straight-forward implementation. As a result, the digital and the analog power converter signals can be traced by means of ChipScope tool, and the processor software can be traced by means of a software debugger tool.

Temperature Influence on Equivalent Impedance and Efficiency of Inductor Systems for Domestic Induction Heating Appliances

Domestic induction heating systems exhibit temperature dependence on its main characteristics. In the past, analytical expressions of the equivalent impedance and efficiency were derived for a constant temperature planar inductor coil system. In this paper, extended expressions including thermal effects are proposed and, finally, experimentally validated by means of measurements and a FEM simulation.

A new ZVS two-output series-resonant inverter for induction cookers obtained by a synthesis method

Multiple-burner induction cookers are suitable for using multiple-output inverters. Some state-of-the-art techniques use several single-output inverters or a single-output inverter multiplexing the loads along the time periodically. A state-space model proposed for switched converters is applied here as a synthesis tool for generating a two-output inverter. By specifying a two-output series-resonant high-frequency inverter, a new inverter for induction cookers is obtained fulfilling the requirements. The synthesized converter allows the control of the two outputs, simultaneously and independently, up to their rated powers saving component count compared with the two-converter solution.

Electromagnetic induction of planar windings with cylindrical symmetry between two half-spaces

A closed-form solution is derived for the equivalent impedance of a planar winding with cylindrical symmetry placed between two half-spaces. This is basically the structure of a domestic induction heating appliance comprised of a planar winding, a metallic vessel, and a lossless magnetic substrate. The first matter addressed is the impedance of a sandwiched single-turn coil, obtained by using the vector potential Helmholtz equation solution, and the result is generalized to n-turn coils. The real part of this impedance represents power dissipated in the form of heat. The proposed model includes geometry dependence, frequency of excitation currents, and electromagnetic properties of both top and bottom media. Enhancement of power dissipation in the conducting media as a result of the inclusion of a magnetic substrate is also explored. Experimental results are presented in order to validate the theoretical model.

EMI improvements using the switching frequency modulation in a resonant inverter for domestic induction heating appliances

In this paper the spread-spectrum technique is applied to a resonant half-bridge inverter for domestic induction heating in order to improve the electromagnetic interference (EMI). This technique has been successfully applied in switching mode power supplies (SMPS). Two different switching frequency modulation strategies are tested and the influence of different modulation parameters is analysed. Both simulation and experimental test bench including inverter and measuring instrumentation are presented. The simulated instruments and detectors are based on homodyne receiver. Finally experimental measures are compared with simulation results.

A new dynamic electrical model of domestic induction heating loads

Traditionally the domestic induction heating load has been electrically modelled by means of the series connection of an energetic equivalent resistance and inductance. Due to the nonlinear nature of the load and the excitation dependence of these equivalent parameters, which are only valid for a given waveform, there exists a strong lack of accuracy in certain situations and applications. In case precise temporal waveform is required a more complex and complete model reproducing dynamic effects must be develop. In this paper a well-known topology for the frequency dependent modelling in the linear case is modified obtaining the Foster series nonlinear network (FSNL) which is able to include both nonlinear and frequency dependent effects providing a complete dynamic behavioural load model. Results are presented for a typical induction heating load which has been characterized using a large-signal and wide frequency (12 kW- 1.5 MHz) measurement testbech. Optimization procedure is explained and performance is tested in the time domain in order to validate the modelling approach.