steadyj
Newbie level 6
pi controller circuit
Hi all, I wanted to check the stability of a PI control loop as in attachment. In circuit, I used the simplest model of OP-AMP, which has rails of +5V and ground, and the open loop voltage gain is 1e+6. It is an idealized OP-AMP model as an accessory in ORCAD, since I am insterested in the general concept of the control loop rather than some specific performance of a type of chip.
I used V2 as a signal source to verify step response. During simulation, I met nonconvergence problems. If the components values are chosen in order to make control loop in oscillation, simulation can't be finished with error message like "Convergence problem in transient analysis at Time = .012 Time step = 9.537E-12, minimum allowable step size = 10.00E-12".
The amazing thing is accidentally I found if the gain of OP-AMP U32 was decreased to 1e+5, then the simulation could be went through. Can anybody familiar with PSPICE explain this phenomenon? Roughly I impute the failure to the accuracy caused by the high gain, since much higher gain needs much higher voltage accuracy on the input port of OP-AMP.
Hi all, I wanted to check the stability of a PI control loop as in attachment. In circuit, I used the simplest model of OP-AMP, which has rails of +5V and ground, and the open loop voltage gain is 1e+6. It is an idealized OP-AMP model as an accessory in ORCAD, since I am insterested in the general concept of the control loop rather than some specific performance of a type of chip.
I used V2 as a signal source to verify step response. During simulation, I met nonconvergence problems. If the components values are chosen in order to make control loop in oscillation, simulation can't be finished with error message like "Convergence problem in transient analysis at Time = .012 Time step = 9.537E-12, minimum allowable step size = 10.00E-12".
The amazing thing is accidentally I found if the gain of OP-AMP U32 was decreased to 1e+5, then the simulation could be went through. Can anybody familiar with PSPICE explain this phenomenon? Roughly I impute the failure to the accuracy caused by the high gain, since much higher gain needs much higher voltage accuracy on the input port of OP-AMP.