Author Topic: LTspice simulation just grinds to a halt?  (Read 1114 times)

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Offline FaringdonTopic starter

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LTspice simulation just grinds to a halt?
« on: January 02, 2023, 07:35:47 pm »
Hi,
Do you know why the attached LTspice sim just stops working at about 56ms?
'Perfection' is the enemy of 'perfectly satisfactory'
 

Offline Warhawk

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Re: LTspice simulation just grinds to a halt?
« Reply #1 on: January 03, 2023, 08:33:40 am »
You're getting cross conduction (check the switch nodes and the current that flows from the power supply).
High-side drivers are goofy. I am not seeing right Vgs voltages.
 
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Offline FaringdonTopic starter

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Re: LTspice simulation just grinds to a halt?
« Reply #2 on: January 03, 2023, 06:16:54 pm »
Thanks,  the LTspice sim now works, as attached,  but is extremely slow...any tips on speeding this particular sim up appreciated?
'Perfection' is the enemy of 'perfectly satisfactory'
 

Offline Warhawk

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Re: LTspice simulation just grinds to a halt?
« Reply #3 on: January 04, 2023, 11:46:57 am »
Thanks,  the LTspice sim now works, as attached,  but is extremely slow...any tips on speeding this particular sim up appreciated?

You can try the Alternate solver in the LTspice settings. Your simulation takes time because you likely face convergence problems. This often happens when something is "wrong".
In general, the SPICE simulation engine is not well suited for switch mode simulations. Tools like PLecs or Simplis do a way better job.

LT spice is a great tool and I use it frequently but only for fundamental simulations. Garbage in=garbage out. For example, I replace gate drivers with logic gates and ideal diodes for the current limit, etc.

edit: Grammar
« Last Edit: January 06, 2023, 02:40:00 pm by Warhawk »
 
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Online SiliconWizard

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Re: LTspice simulation just grinds to a halt?
« Reply #4 on: January 05, 2023, 08:19:53 pm »
Yeah switching power supplies are slow to simulate with Spice engines. One way of making it faster is to make sure you have slower transitions (but then that may not be the circuit you really want to simulate). Very short rise/fall times are what makes simulation slow.

For their own switching regulator models, LTSpice uses internal mixed-signal models that are fully optimized and are thus not 100% simulated using pure Spice. Of course you don't have access to all of those optimizations when using only basic parts and full Spice simulation.

 
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