Modelling the Half-Bridge Series Resonant Converter Using the MISSCO Approach

Use of the concept of minimum separable switching configuration (MISSCO) has been proved particularly fruitful in generating circuit-oriented models that describe the statics and dynamics of PWM and quasi-resonant converters. The essence of this approach lies in the separation of the essential switching part of the circuit and the subsequent application of averaging to yield an appropriate time-invariant model for the circuit. In this paper, the same general approach is extended to resonant converters, but with a slightly different treatment for the part where averaging cannot be directly applied as a consequence of the natural frequency being close to the switching frequency. In particular, a complete dynamic model for the half-bridge series-resonant converter operating in continuous mode is derived which agrees perfectly with experimental results.