Control Strategies for Class-E Resonant Inverter with Wide Load Variation

The main advantage of resonant converters is the soft-switching conditions (SSC). The switching losses can be drastically reduced turning the power devices at zero-voltage switching (ZVS) or zero-current switching (ZCS). This allows to operate at higher switching frequency and to reduce the components size. Unfortunately, this condition can be achieved only at an optimal operating point. For example, if load variation occurs, the achievement of SSC is not guaranteed, producing more switching losses and therefore reducing the system efficiency. To overcome this problem and ensure ZVS over a wide load variation, two control strategies are presented. Their application to a ClassE inverter is investigated, but the principle can be applied to all resonant converters. Both control methods are based on components variations. The first technique changes the inductance L while the second one changes the capacitances C and C-1. The control algorithms are carried out and simulation results are given to validate the proposed algorithms.