Re: LTSpice Error Massage: time step too small

Discussion in 'Electronic Design' started by Jeroen Belleman, Aug 28, 2008.

  1. Elk wrote:
    > Hello,
    >
    > I try to simulate a circuit, but I always get an error message:
    > Analysys: time step too small; initial timepoint: trouble with
    > u3:mm-instance m:u3:1
    >
    > u3 is a Mosfet IRF4905.
    >
    > Has anyone an idea how I can solve the problem?


    Oh dear! A switching power supply. Debugging those is *work*,
    of which I have quite enough, thank you.

    I've spent a few minutes trying to simulate the thing, after
    having whimsically substituted LT1018s for the comparators,
    NPN, PNP and PMOS generics for the transistors I don't have
    the models for (i.e., all of them), and fixing the values of
    some caps and the coils, which seemed garbled.

    I don't see what the circuitry involving Q4 and Q5 with the
    amplifiers driving them is for either.

    The simulation runs without the error you described, but the
    circuit doesn't work. I'd say, try to increase the PMOS gate
    series resistor to 50 Ohms and/or insert resistors in the
    collector leads of the driver transistors. A few tens of ohms
    might do it.

    I'm sorry but I can't afford to put in the time required to
    go any further.

    Jeroen Belleman
     
    Jeroen Belleman, Aug 28, 2008
    #1
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