IMPROVED PULSE DENSITY MODULATION FOR HIGH-FREQUENCY SERIES RESONANT INVERTER WITH TRANSFORMER-COUPLED LOAD

An improved method to determine the pulse density modulation (PDM) pat tern is proposed for the high-frequency series resonant inverter (SRI) with a load-matching transformer. A simple discrete-time model of SRI is derived and the constraints given by a load-matching transformer a re analysed. Using the model and constraints, the optimal PDM pattern is derived. The output current ripple is much reduced with this method and the transformer saturation problem can also be avoided. The resul ts of a prototype experiment verify that the unwanted spectral compone nt in the output current is effectively decreased by the optimal patte rn. It is believed that the proposed technique is useful for practical applications such as the high-frequency power supply of an induction heating system.