Development and optimisation of a solid-state pulsed power supply for a CO₂ TEA laser

[摘要] ENGLISH ABSTRACT:With technological advances in solid-state switches the modernization of conventional pulsedpower supplies utilizing thyratrons has become possible. A novel pulsed power supply is designedwhere two series-stacked IGBTs (rated at 1700 V and 300 A each) are used to replace a thryatrondrivenpulsed power supply for a mini CO2 TEA laser.The mini CO2 TEA laser is firstly characterized in order to optimize the design of the pulsed powersupply. It is found that stable laser discharges can be obtained with electrode voltage rise-times of150 ns or less. Furthermore, the optical output energy and the efficiency of the laser have beensignificantly increased by reducing the peaking capacitor size of the pulsed power supply.The two stacked IGBTs switch a C-C transfer loop and the generated pulse is stepped up by a pulsetransformer and is compressed by a two-stage magnetic pulse compression unit. Theoretically andthrough measurements it is shown that automatic voltage sharing between the two IGBTs can beobtained if the turn-on time of the IGBTs is much faster than the transfer time of the switched C-Ctransfer loop. Lifetime tests reveal that high-power IGBTs are able to reliably switch pulses withpeak currents between 4 and 5 times the rated average current of the device. Under laser faultconditions, i.e. laser arcing or missing laser discharges, the reliability of the pulser can be increasedby using over-voltage snubbers. In addition, it was found that the internal diode of IGBT modulescan eventually fail under the prevalence of laser fault conditions.A modular construction approach is used where components of the pulsed power supply are preassembled.A new rectangular layout of the magnetic pulse compression unit is utilized in order tominimize size and simplify the final construction and assembly.

[发布机构] Stellenbosch University