Open Innovation: The New Imperative for Creating and Profiting from Technology

Induction heating (IH) technology is nowadays the heating technology of choice in many industrial, domestic, and medical applications due to its advantages regarding efficiency, fast heating, safety, cleanness, and accurate control. Advances in key technologies, i.e., power electronics, control techniques, and magnetic component design, have allowed the development of highly reliable and cost-effective systems, making this technology readily available and ubiquitous. This paper reviews IH technology summarizing the main milestones in its development and analyzing the current state of art of IH systems in industrial, domestic, and medical applications, paying special attention to the key enabling technologies involved. Finally, an overview of future research trends and challenges is given, highlighting the promising future of IH technology.

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Induction Heating Technology and Its Applications: Past Developments, Current Technology, and Future Challenges

An LCL-T resonant converter (LCL-T RC) is shown to behave as a current source when operated at resonant frequency. A detailed analysis of the LCL-T RC for this property is presented. Closed-form expressions for converter gain, component stresses, and the condition for converter design optimized for minimum size of resonant network is derived. A design procedure is illustrated with a prototype 200-W 20-A current-source power supply and experimental results are presented. The LCL-T RC as a current source offers many advantages such as easy parallel operation and low circulating currents at light load. Additionally, with appropriate phase shift in paralleled modules, the peak-peak ripple in output current is reduced and the ripple frequency is increased, reducing filtering requirements. The leakage inductance of a transformer can be advantageously integrated into the resonant network. These merits make the topology applicable in various applications such as magnet power supply, capacitor charging power supply, laser diode drivers, etc.

Analysis and design of an LCL-T resonant converter as a constant-current power supply

Domestic induction cookers operation is based on a resonant inverter which supplies medium-frequency currents (20-100 kHz) to an inductor, which heats up the pan. The variable load that is inherent to this application requires the use of a reliable and load-adaptive control algorithm. In addition, a wide output power range is required to get a satisfactory user performance. In this paper, a control algorithm to cover the variety of loads and the output power range is proposed. The main design criteria are efficiency, power balance, acoustic noise, flicker emissions, and user performance. As a result of the analysis, frequency limit and power level limit algorithms are proposed based on square wave and pulse density modulations. These have been implemented in a field-programmable gate array, including output power feedback and mains-voltage zero-cross-detection circuitry. An experimental verification has been performed using a commercial induction heating inverter. This provides a convenient experimental test bench to analyze the viability of the proposed algorithm.

Load-Adaptive Control Algorithm of Half-Bridge Series Resonant Inverter for Domestic Induction Heating

This paper presents and analyzes the asymmetrical voltage-cancellation (AVC) control, a generalized control technique for resonant inverters. It is applied to the popular full-bridge series resonant inverter. The proposed control technique achieves better efficiency performances than conventional fixed-frequency control strategies, while considering zero-voltage-switching operation, output power and load variations. The theoretical results are verified experimentally, using a prototype for an induction-heating cooking appliance.

Asymmetrical voltage-cancellation control for full-bridge series resonant inverters

Multiple-burner induction-heating cooking appliances are suitable for using multiple-output inverters. Some common approaches use several single-output inverters or a single-output inverter multiplexing the loads along the time periodically. By specifying a two-output series-resonant high-frequency inverter, a new inverter is obtained fulfilling the requirements. The synthesized converter can be considered as a two-output extension of a full-bridge topology. It allows the control of the two outputs, simultaneously and independently, up to their rated powers saving component count compared with the two-converter solution and providing a higher utilization of electronics. To verify theoretical predictions, the proposed converter is designed and tested experimentally in an induction-heating appliance prototype. A fixed-frequency control strategy is digitally implemented with good final performances for the application, including ZVS operation for active devices and a quick heating function. Although the work is focused on low-power induction heating, it can be probably useful for other power electronic applications.

A two-output series-resonant inverter for induction-heating cooking 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.

The domestic induction heating appliance: An overview of recent research

A synthesis method for generating switched electronic converters from some given specifications is presented. This method is based on a general state-space model for switched converters previously proposed. A synthesis procedure is outlined including the selection of the converter type, the selection of converter configurations, and the insertion of proper switches. Although the treatment presented here requires some experience and intuition, it is not restricted to a specific class of converters. The method is a generic computer-aided tool to search for topologies with given attributes. As an illustrative example, by specifying a resonant sine-wave inverter, a new family of converters is derived and one of its members is implemented and tested.

A synthesis method for generating switched electronic converters

Collaboration between Industry and University is becoming more important in order to improve the competitiveness of the research and development activities. Moreover, establishing synergies to bridge the gap between the academic and industrial spheres has demonstrated to be advantageous for both of them. Nowadays, Industry is moving towards an open innovation structure, in which external agents as universities play a key role. Besides, University is also seeking a more active learning methodology to improve the education of students for the real world. Considering this framework, a special effort should be done to take advantage of the collaborative work between Industry and University. The aim of this paper is to present the collaborative framework and the benefits obtained of the educational activities as a consequence of the long-term collaboration established between the University of Zaragoza and the Bosh and Siemens Home Appliances Group. The key stones of the collaboration are presented, and the po...

Educational opportunities based on the university-industry synergies in an open innovation framework

Generally, power inverters for induction cooking appliances are controlled by varying frequency to control current through the inductor coil When more than one power converter is operated at different frequencies greater than audible noise upper threshold, low frequency interharmonics are generated in common impedance due to nonlinear effects Suppression of audible noise in multiple-coils induction cookers leads to high-performance fixed-frequency control This paper presents a new unipolar voltage-cancellation control for series resonant inverters This control strategy is used in full-bridge topologies for induction cookers, allowing fixed frequency control with ZVS operation over a wide power range Performance of current-mode and voltage-cancellation is improved This control is implemented in a series-resonant full-bridge inverter for induction cookers using IGBTs and digital control implemented in a PLD which can be easily implemented in an ASIC for mass production

J.R. Garcia

Papers

A two-output series-resonant inverter for induction-heating cooking appliances

The domestic induction heating appliance: An overview of recent research

A synthesis method for generating switched electronic converters

Educational opportunities based on the university-industry synergies in an open innovation framework

Unipolar voltage-cancellation control of resonant inverters for induction cooking appliances