L.A. Barragan

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

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.

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.

Efficiency-Oriented Design of ZVS Half-Bridge Series Resonant Inverter With Variable Frequency Duty Cycle Control

The efficiency of zero voltage switching half-bridge series resonant inverter can be decreased under certain load conditions due to the high switching frequencies required. The proposed variable frequency duty cycle (VFDC) control is intended to improve the efficiency in the medium and low output power levels because of the decreased switching frequencies. The study performed in this letter includes, in a first step, a theoretical analysis of power balance as a function of control parameters. In addition, restrictions due to snubber capacitors and deadtime, and variability of the loads have been considered. Afterward, an efficiency analysis has been carried out to determine the optimum operation point. Switching and conduction losses have been calculated to examine the overall efficiency improvement. VFDC strategy efficiency improvement is achieved by means of a switching-frequency reduction, mainly at low-medium power range, and with low-quality factor loads. Domestic induction heating application is suitable for the use of VFDC strategy due to its special load characteristics. For this reason, the simulation results have been validated using an induction heating inverter with a specially designed load.

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

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.

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

In this paper, the frequency-dependent resistance in Litz-wire planar windings for domestic induction heating appliances is analyzed. For these inductors, in which the size is not an essential constraint, an analytical model is developed based on the superposition of different loss effects in the wire. Eddy current losses, including conduction losses and proximity-effect losses, both internal and external, were considered and modeled. The magnetic field necessary to evaluate the external proximity losses is as well analytically calculated considering the complete winding and load properties. To verify this model and its limitations, several inductors with different wires and numbers of turns were constructed and results with both non-loaded and loaded inductors are compared with theoretical predictions.

A Versatile Power Electronics Test-Bench Architecture Applied to Domestic Induction Heating

The design of new power-converter solutions optimized for specific applications requires, at a certain step, the design and implementation of several prototypes in order to verify the converter operation. This is a time-consuming task which also involves a significant economical cost. The aim of this paper is to present a versatile power electronics architecture which provides a tool to make the implementation and evaluation of new power converters straightforward. The adopted platform includes a versatile control architecture and a modular power electronics hardware solution. The control architecture is a field-programmable-gate-array-based system-on-programmable-chip solution which combines the advantages of the processor-firmware versatility and the effectiveness of ad hoc paralleled digital hardware. Moreover, the modular power electronics hardware provides a fast method to reconfigure the power-converter topology. The architecture proposed in this paper has been applied to the development of power converters for domestic induction heating, although it can be extended to other applications with similar requirements. A complete development test bench has been carried out, and some experimental results are shown in order to verify the proper system operation.

Series-Resonant Multiinverter for Multiple Induction Heaters

Multiple-load and multiple-source systems are widely present in the current technology. These systems require controlling either the supplied voltage or power to several loads with different requirements simultaneously. As a consequence, the cost and size of the power stage may increase beyond the admissible limits for certain applications. Considering multiple-inductor loads, a novel series-resonant multiinverter topology is proposed to obtain a cost-effective and high-power density solution. The converter is based on a common inverter block and a resonant-load block. The performed analysis includes the description of the operation modes and the control strategy analysis. Domestic induction heating has been considered for application due to its special cost and size requirements, and the extensive inductor use. The proposed converter has been designed and validated experimentally through a prototype, which includes the power converter and the field-programmable gate array-based control architecture.

FPGA Implementation of a Switching Frequency Modulation Circuit for EMI Reduction in Resonant Inverters for Induction Heating Appliances

This paper presents the use of frequency modulation as a spread spectrum technique to reduce conducted electromagnetic interference (EMI) in the A frequency band (9-150 kHz) caused by resonant inverters used in induction heating home appliances. For sinusoidal, triangular, and sawtooth modulation profiles, the influence of peak period deviation in EMI reduction and in the power delivered to the load is analyzed. A digital circuit that generates the best of the analyzed modulation profiles is implemented in a field programmable gate array. The design is modeled in a very-high-speed integrated circuits hardware description language (VHDL). The digital circuit, the power converter, and the spectrum analyzer are simulated all together using a mixed-signal simulation tool to verify the functionality of the VHDL description. The spectrum analyzer is modeled in VHDL-analog and mixed-signal extension language (VHDL-AMS) and takes into account the resolution bandwidth stipulated by the EMI measurement standard. Finally, the simulations are experimentally verified on a 3.5 kW resonant inverter operating at 35 kHz.

Series Resonant Multiinverter 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 particularly important for resonant converters as their efficiency significantly reduces when their operation point is set outside their resonant conditions. Considering the importance of efficiency for power converter reliability, environmental impacts, and regulation concerns, a major effort to improve the operation under light-load conditions is justified. Domestic induction heating is an application where variable loads and output power requirements imply 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 series resonant multiinverters, which are a cost-effective topology for supplying multiple inductive loads, based on discontinuous-mode operation. Two different control strategies are proposed: regenerative control and direct conduction control. An analytical study is performed, and the main simulation results are presented. An experimental series resonant multiinverter prototype is used to validate the simulation results.

The domestic induction heating appliance: An overview of recent research

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.