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.