New phase-shifted soft-switching PWM series resonant inverter topologies and their practical evaluations

This paper presents three versions of phase-shifted soft-switching PWM with constant frequency or load-adaptive PFM series resonant inverter topologies. The constant frequency phase-shifted inverter is widely used for high power applications. When soft-switching operation is not realized, the operating frequency range is limited to around 20 kHz. By introducing load-adaptive PFM control, lossless capacitors, lossless inductors, switching losses and stresses are much reduced and the frequency limit is extended to more than 100 kHz for IGBTs for example. These inverters are suitable for induction-heating applications in metal electroheating processing plants, food cooking processing plants, hot water and hot gas producing processing plants