Research On Fractional Model Of PN-junction Diode

PN junction diode is a common simple semiconductor device,and is also the basis onstudying other semiconductor devices.Most PN junction diode models only have analytical models and withoutcircuit model,at the same time,the complexity and accuracy of diode modelscan not be satisfied.In this thesis,we combine the theory of semiconductor physics,circuitthoeryandfractional calculus which is the current research hotspot.The fractional vector fitting method is appliedto approximate the full current equation,and the nonhomogeneous order coefficientis optimized bynon-linear least square method,thenwe derive a new fractional model of PN junction long-base diode.In addition,the model parameters are extracted accroding tothe reverse recovery method andthe transcendental equations solution.For the switching characteristic of the diode,this thesis mainly analyzes the reverse transient response of the fractional-order model to simulate the dynamic characteristic of PN junction diode.The simulation results of the fractional model are obtained by fractional-order predict-correction method.On the other hand,the fractional-order model compared with the experimental result,the high-order dynamic model alsoshows that the fractional-order model can better simulate the reverse transient characteristics of a long-base diode,by the way,itcan predictsthe minority carrier storage timeaccurately.Fractional small-signal circuitmodelis derived from local linearization of fractional-order model.Normalized admittance of fractional small-signal modelis compared with the higher-order dynamic model and small-signal admittance function.According to experimental results,it is found that the fractional-order model has a better effect onsimulating the frequency-off characteristic of the PN junction diode.