Silicon_Power_ex01.in : Reverse Recovery of a Power Diode

Home> Silicon>

Silicon_Power_ex01.in : Reverse Recovery of a Power Diode

Every software package contains a full set of examples suitable for that version and are installed with the software. If you see examples here that are not in your installation you should consider updating to a later version of the software. These examples can be used by beginners and advanced users for product evaluation, teaching purposes, and self-training.

Required Modules

Victory Device:

2D Simulator
2D MixedMode

This example demonstrates the reverse recovery of a silicon power diode. It shows:

Structure definition using Victory Device

The SPICE-like command syntax for simulating MixedMode circuits

Steady state and transient analysis of a power diode

The structure consists of a rectangular silicon power diode. Victory Device is used to define the power diode structure including mesh, materials, electrodes, and doping. The MESH statement defines a rectangular mesh with grid lines at the locations specified by the X.MESH and Y.MESH statements. The entire mesh is defined as one silicon region using the REGION statement. Electrodes are defined on top and bottom, and the DOPING statement is used to define a uniform background concentration and gaussian n-type and p-type regions. This structure is saved and will be used as a device by MixedMode.

In this simulation, the MixedMode circuit simulator uses Victory Device to calculate the electrical characteristics of the power diode under the specified circuit conditions. First, a steady-state simulation of the power diode circuit is performed.

The .BEGIN and .END statements indicate the beginning and end of the MixedMode syntax. The MixedMode commands are similar to those used in SmartSpice. Circuit components, topology, and analysis are defined within. In general, the circuit component definition consists of three parts: the type of component, the lead or terminal node assignments, and the component value or model name. For example, the first component definition in this simulation is a DC voltage source. V1 defines the component as voltage source number one, 1 and 0 are the two circuit nodes for this component, and 1000 indicates that the voltage source value is 1000 volts. The remaining circuit components are resistors R1 and R2, inductor L1 and independent current source I1. The ADIODE statement specifies a device to be analysed by Victory Device. The A part of the ADIODE command specifies that this is a device statement. The DIODE portion simply defines the device name. The option INFILE= indicates which device structure file is to be used. The .NODESET statement defines the initial values for node voltages and the .SAVE OUTFILE= statement stores the result to the indicated file. Since this is the steady state solution, no output log data file is needed. Additionally, the .OPTION statement sets the solution method to a modified two-level Newton using the M2LN parameter. Other command line options exist. Please refer to the MixedMode section of the Victory Device user’s manual for a complete list.

To completely specify the simulation, the physical models used by Victory Device must be specified. The MODEL statement is used to turn on the appropriate transport models. This set includes CONMOB: the concentration-dependent mobility model, FLDMOB: the lateral electric field-dependent mobility model, CONSRH: Shockley-Read-Hall recombination using concentration dependent lifetimes, AUGER: Auger recombination accounting for high level injection effects, and BGN: band gap narrowing. Refer to the Victory Device user’s manual for a description of these models. The MATERIAL statement is used to override default material parameters. In this case, the carrier recombination fixed lifetimes are set. Finally, an impact ionization model is enabled using the IMPACT statement with the SELBERHERR parameter. This specifies that the Selberherr impact ionization model is to be used.

The next step is the transient analysis which is specified in a similar manner. The reverse recovery of the diode is simulated by dropping the value of output resistor R2 over a small increment of time. The R2 statement contains additional syntax to perform this task. Here, the resistor is treated as a source whose resistance decreases exponentially from 1 MOhm to 1 mOhm over the specified time step. This action essentially shorts out the parallel current source I1 which is also connected to the anode of the diode. The .TRANS statement is used to specify the time stepping parameters for the transient analysis. In addition, the .LOG statement saves the diode output characteristics over the time interval specified. When the transient analysis is completed, Victory Visual plots the transient reverse recovery of the power diode.