| Electronics > Projects, Designs, and Technical Stuff |
| Spice Limitations? |
| << < (3/3) |
| Ian.M:
I've got it semi-cracked. The model doesn't like excessive Vce dV/dt during powerup or the turnoff risetime. A small emitter resistance seems to make it less sensitive to fast risetimes. but ultimately with an inductive load the only way that lets it work for repeated pulses without blowing out with Def Con>50 and a timestep too small error on an internal diode, is to limit the dV/dt with a diode, capacitor and discharge resistor snubber. Inductive load sim attached. Its looking good under both the standard and alternate solver SPICE engines, and runs without any .option convergence hacks. The hacks I tried are there but commented out. I still cant get it to find the operating point in a reasonable length of time without risking it bombing out so it uses .tran uic and to get to a steady state starting condition in a reasonable runtime, ramps up the supply over 225ns while clamping the lower IGBT gate to ground and clamping across the upper IBGT for 250ns to minimise Miller effects on the model internals. You'll have to get cleverer than .ic if you want to set I(L1) effectively. I would suggest a pulsed voltage source in series with it that can drive it to the required current while the upper IGBT is shorted during the sim startup. I've also put my parametrised .measure script for automated 10% to 90% rise and fall time measurement on the sim. Move the R_X_X Vout X_X 1 that connects the signal to be measured to the script out to the sim if you want to make the script a separate file and run it as post-processing after a successful sim run. |
| Glenn0010:
Hi Ian, Thanks for all your help! I am currently on holiday and showing my parents round so I won't have time to have a look at it till the end to the month. I'll have a look at what you did when I get back. I was also thinking of running the same simulation with the IKW25T120 as it's a simialr device and hope that infineon's SPICE Model is better than the OnSemi. Thanks again for your help! I'll have a look at it when I get back! Cheers |
| Navigation |
| Message Index |
| Previous page |