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LT Spice - Analysis problem : timestep too small

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droseman

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Hello,

I am attempting to simulate a flyback power supply using LTSpice, I am using coupled inductors to simulate the transformer and a series diode and capacitor across the secondary to remove high voltage spikes.

I am doing a transient analysis .tran 0 100u 0.1u, but when I add the diode on the secondary, I get Analysis: time step too small, and only around 6us of the 100 us span gets simulated. When I remove the diode, I get the whole 100us span.

What could be the issue with this diode which halts the simulation?

NB I can't post netlist or schematic, but it is a fairly conventional flyback converter.

Thanks
Dave
 

keith1200rs

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I have found LT Spice to be fairly unreliable and seen similar problems. Try adding a small resistor in series with the diode and/or inductors and see if that helps. Make sure you don't have perfect inductors with no resistance - that can cause infinite voltages/currents.

Keith.
 

droseman

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Re: [SOLVED] LT Spice - Analysis problem : timestep too small

I've fixed the issue which was causing my simulation to crash.

I changed the ABSTOL VOLTOL and Gmin values to 2 magnitudes less and I got a successful simulation which was approximately what I was expecting. I suspect that my circuit was on the limit of complexity for finding a solution, as making small changes could make the simulation fail again.

Thanks Keith for your assistance

--dave
 

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