Study On Turn-off Characteristics And Evaluation Methods Of RSD

RSD (Reversely Switched Dynistor) is a new power electronic switch which is basedon the principle of controlled plasma layers, easily to trigger, simple the driver circuit,capability with large dI/dt and dU/dt, high power density, easily to use in series and/orparallel, low cost, long lifetime are the RSD unique advantages. These advantages makethis new switch-RSD have a bright application in the pulsed power area.Firstly, the pulsed power technology and the development of the power electronicdevices are introduced in this thesis, the working principle of the RSD are studied. Basedon the trigger and turning on mechanism of RSD, two trigger methods are analyzed, theknowledge of the magnetic switch are also studied. Then, choosing the proper circuittopology and designing the values of the different components, simulations are performed.According to the simulation results, the turn off characteristics of RSD are analyzed, alsothe assessment method of the turn off characteristics. At last, the concepts of quasi-turn offtime and relative turn off time are proposed, which will have crucial meanings in therepetitive pulsed power area.Based on the analyzing of the simulation results, the values of each component in thepre-charging circuit: voltage-400V, capacitor-1μF, inductance-0.4μH and resistance-0.3Ωare selected, these values meet the requirements of the pre-charging and shorten thesimulation time. In order to isolate the main circuit and the pre-charge circuit when thepre-charging is finish, a variable resistor which the resistance changes from0to200MΩseries connects in the pre-charge circuit, the resistance changes from0to200MΩ in a fewten ns after2μs. The simulation results show that: the turn off time is increasing with theincrease of the minority carrier lifetime, the main current decreasing rate dI/dt and themeasured voltage. The quasi turn off state is the state when the measured voltageaccording to the decreasing the carrier density unable to recover to the on state voltage ofthe RSD, the corresponding turn off time is defined quasi turn off time. Quasi turn offstate is determined by the working condition of RSD and the level of the disturbingvoltage caused by the environment, different quasi turn off state has different quasi turn off time, the higher the disturbing voltage, the longer quasi turn off time. This newconcept has instructional and positive meanings in the repetitive pulsed power area.