Similar time step problem with TCA 785

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Harish Kidambi

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Hi..
The circuit attached is the triac controlling circuit,and the problem is
Simulation starts and interrupts shortly. The error message is: Timestep too small, time=xxxx, timestep=yyyy, trouble with node zzzz.
Can anyone give me some idea please, what is going on here, am I doing something wrong or this is software/model bug?


Any ideas would be appreciated.

Thanks.
 

The Timestep error is not a software bug but it is a common occurrence in Spice simulator simulations when it has a problem converging to a solution in the calculations, often occurring when there is an abrupt change in the simulation voltages, such as the SCR turning on.

A couple things to try:

1. Change the program Integration Method from Trapezoidal to Gear.

2. Increase the simulation accuracy limits on Abstol, Reltol, etc. by a factor of 10. This will reduce the simulation accuracy somewhat but may allow the simulation to continue.
 

Although this is a general SPICE simulator problem, different simulators have partly different means to handle it. Did you review the Troubleshooting/Convergence Problems paragraph in the Proteus help?

Taking a second look at your circuit, it seems that this comment in the manual perfectly fits your problem:
Most convergence errors are due to badly drawn circuits or incorrect models.
Click to expand...
Please show me the return path for the triac gate current in your circuit.
 

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