An FPGA-Based Gain-Scheduled Controller for Resonant Converters Applied to Induction Cooktops

Domestic induction heating appliances have become popular due to their advantages such as efficiency, fast heating, cleanliness, and safety. In order to achieve high efficiency, induction cooktops usually features resonant converters in which the inductor-vessel system is a part of the resonant tank. Thus, the inductor-vessel system impedance sets the point of operation of the power converter. Due to the variability of the load with multiple parameters such as temperature, geometry, and material, the resonant converter has to work with highly varying operating conditions. When designing a classical controller, the controller gain is selected to assure the system stability in the whole range of operation and for a large amount of vessels. This study proposes an FPGA-based gain scheduled controller which makes use of the information of the modulation parameters and an online impedance identification system. As a result, the proposed controller significantly improves the converter dynamic response, improving the performance and safety operation of the power converter. The proposed control algorithm has been experimentally verified using a domestic induction heating prototype, proving the feasibility of this proposal.