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Electronics Forum / CAD / March 2008pspice changing time step issue
I have a couple issues I'm having trouble with, I'm using orcad 16 and trying to simulate a simple circuit, it's basically two pulse generators VPULSE each going through a diode... I'm trying to "diode- or" two voltage sources... but I keep getting these large voltage spikes.... say if I set the pulses at 12V I get these 16V spikes... and then they settle to 12V here is my circuit, where V1 and V2 are 12 Volt pulses slightly offset from one another... I was especting to seee 12 V on the Vout regardless of whether V1, V2 or both were on V1 O-----|>|------- D1 | |-------------O Vout | V2 O-----|>|------- D2 My other issue is, I try to set my pulses for 1 second each and then want my simulation to go to 3 seconds, but it takes forever to run through the simulation, does anyone know how I can speed that up.... can I change the sampling rate or something so it would fnish faster? Much thanks J. > I have a couple issues I'm having trouble with, I'm using orcad 16 and > trying to simulate a simple circuit, it's basically two pulse [quoted text clipped - 16 lines] > through the simulation, does anyone know how I can speed that up.... > can I change the sampling rate or something so it would fnish faster? Do you have a load resistor on the circuit or is the two diodes the whole thing? Spice sometimes gives wild results for circuits that won't work. With no load resistor, the Vout node is basically floating when the two diodes are off. > > I have a couple issues I'm having trouble with, I'm using orcad 16 and > > trying to simulate a simple circuit, it's basically two pulse [quoted text clipped - 25 lines] > > - Show quoted text - I do have a load resistor.... and also grounds, would you expect a voltage spike in a circuit like this? > > > I have a couple issues I'm having trouble with, I'm using orcad 16 and > > > trying to simulate a simple circuit, it's basically two pulse [quoted text clipped - 28 lines] > I do have a load resistor.... and also grounds, would you expect a > voltage spike in a circuit like this? No I wouldn't. What sort of diodes is it and what sort of spice? > I have a couple issues I'm having trouble with, I'm using orcad 16 and > trying to simulate a simple circuit, it's basically two pulse [quoted text clipped - 19 lines] > Much thanks > J. Do you want access to China's massive pool of electronic manufacturers... but lack the time to contact suppliers, negotiate contracts, arrange shipping or monitor product quality? Don't worry - Let seriouswholesale deal with all that for you. *Check out the huge range of Gadgets, MP3 / MP4 Players, Car DVD / Audio, and Computer Accessories now by visiting the online wholesale catalog at seriouswholesale. com You'll have peace of mind thanks to the seriouswholesale Quality Control, 12-month Warranty on all products, and easy secure payment by credit card through Paypal. Selling on eBay or your own online store? Send products direct from our warehouse to your customers using our unique drop-shipping service. You can profit by selling hundreds of different products, without holding any of your own inventory! Any questions you have will be answered by the seriouswholesale English-speaking customer support team... Their aim is to make your China electronics importing business easier to run than ever before. Welcome to http://www.seriouswholesale.com. seriouswholesale - Buy from the source, profit without the hassle. - 12 Months Warranty - No minimum order restrictions - Drop-shipping with no additional fee - Pay by safely by PayPal seriouswholesale Wholesale Co., Ltd.: Chinas original and best online electronics wholesaler & drop-shipper: seriouswholesale. com > I have a couple issues I'm having trouble with, I'm using orcad 16 and > trying to simulate a simple circuit, it's basically two pulse [quoted text clipped - 19 lines] > Much thanks > J. Hello, You might reduce the minimum conductance (GMIN). Depending on the load resistance you can reduce it significantly. Also check your maximum step size. As this is 1us, it takes 3e6 steps to run the simulation. Regarding the spikes. When you have a pulse source with 1us rise and fall times, you may reduce the maximum step size to below 1us (but this will cause long sim times when you run for 3s). Other option is increase the rise and fall times of your pulse sources and increase the step size also, this will speed up your simulation. What type of diode do you use? Try another one (for example a 1n4148) and see what happens). Keep in mind that real diodes have capacitance. When the output is already 12V, you can get a spike via the diode that has been connected to the source that goes from low to high. So it may not be a simulation error. When I have doubts about a circuit, I play with the max step size setting. Best regards, Wim PA3DJS www.tetech.nl remove abc from the mail address. > > I have a couple issues I'm having trouble with, I'm using orcad 16 and > > trying to simulate a simple circuit, it's basically two pulse [quoted text clipped - 49 lines] > > - Show quoted text - I keep getting errors like this now: "ERROR -- Convergence problem in transient analysis at Time = .133 Time step = 72.00E-21, minimum allowable step size = 1.000E-18 These voltages failed to converge: V(N902046) = 5.041uV \ 2.644uV These supply currents failed to converge: I(V_V1) = 2.343mA \ -5.677uA I(V_V2) = 2.354mA \ 4.846uA These devices failed to converge: X_D1.D1 " How do I change the step size? I see maximum step size option, but no minimum... wouldn't I want to change the minimum step size to make the simulation run faster? Do you know what these errors mean? Thanks >I have a couple issues I'm having trouble with, I'm using orcad 16 and > trying to simulate a simple circuit, it's basically two pulse [quoted text clipped - 19 lines] > Much thanks > J. Hello panfilero, Please show your SPICE netlist, if you are interested in a helpful answer. It's the .net and the .cir file. Best regards, Helmut On Mar 14, 3:00 pm, "Helmut Sennewald" <helmutsennew...@t-online.de> wrote: > >I have a couple issues I'm having trouble with, I'm using orcad 16 and > > trying to simulate a simple circuit, it's basically two pulse [quoted text clipped - 29 lines] > > - Show quoted text - Hi Helmut, Here's my netlist and .cir files... thanks for taking a look at this * source Test_ X_D1 N899662 N901787 D120NQ045 X_D2 N900764 N901787 D120NQ045 V_V1 N899662 0 +PULSE 12 0 15u 1n 1n 1 2 V_V2 N900764 0 +PULSE 12 12 0 1p 1p 1 2 ** Creating circuit file "Test_.cir" ** WARNING: THIS AUTOMATICALLY GENERATED FILE MAY BE OVERWRITTEN BY SUBSEQUENT SIMULATIONS *Libraries: * Profile Libraries : * Local Libraries : * From [PSPICE NETLIST] section of C:\OrCAD\OrCAD_16.0\tools\PSpice \PSpice.ini file: .lib "nom.lib" *Analysis directives: .TRAN 0 3 0 .PROBE V(alias(*)) I(alias(*)) W(alias(*)) D(alias(*)) NOISE(alias(*)) .INC "..\SCHEMATIC1.net" .END On Mar 14, 3:00 pm, "Helmut Sennewald" <helmutsennew...@t-online.de> wrote: > "panfilero" <panfil...@gmail.com> schrieb im > Newsbeitragnews:67d261ba-2ce3-49fd-9447-fb4c83f9395a@s12g2000prg.googlegroups.com... [quoted text clipped - 32 lines] > > - Show quoted text - Hi Helmut, Here's my netlist and .cir files... thanks for taking a look at this * source Test_ X_D1 N899662 N901787 D120NQ045 X_D2 N900764 N901787 D120NQ045 V_V1 N899662 0 +PULSE 12 0 15u 1n 1n 1 2 V_V2 N900764 0 +PULSE 12 12 0 1p 1p 1 2 Hello, I have looked at your circuit and simulated it with LTspice. It's quite normal to see the large voltage spike at the output, because your diodes have a few nano-Farads capacitance and you drive it extremely "hard" with your voltage sources (Trise=1ns, Ri=0Ohm). The junctiom capacitance is the reason for the voltage spikes. (SPICE model: CJO=11.509E-9) If you add a capacitor to the output, the spikes will become very small. Best regards, Helmut ** Creating circuit file "Test_.cir" ** WARNING: THIS AUTOMATICALLY GENERATED FILE MAY BE OVERWRITTEN BY SUBSEQUENT SIMULATIONS *Libraries: * Profile Libraries : * Local Libraries : * From [PSPICE NETLIST] section of C:\OrCAD\OrCAD_16.0\tools\PSpice \PSpice.ini file: .lib "nom.lib" *Analysis directives: .TRAN 0 3 0 .PROBE V(alias(*)) I(alias(*)) W(alias(*)) D(alias(*)) NOISE(alias(*)) .INC "..\SCHEMATIC1.net" .END On Mar 14, 4:48 pm, "Helmut Sennewald" <helmutsennew...@t-online.de> wrote: > On Mar 14, 3:00 pm, "Helmut Sennewald" <helmutsennew...@t-online.de> > wrote: [quoted text clipped - 84 lines] > > - Show quoted text - I"ll try that, I really appreciate the help! Thanks On Mar 14, 2:48 pm, "Helmut Sennewald" <helmutsennew...@t-online.de> wrote: > On Mar 14, 3:00 pm, "Helmut Sennewald" <helmutsennew...@t-online.de> > wrote: [quoted text clipped - 54 lines] > It's quite normal to see the large voltage spike > at the output, because your diodes have a few nano-Farads Clarification: if 12V=Large the above is correct if 1000V= large this isn't what you were seeing Most likely you saw 12V spikes. > capacitance and you drive it extremely "hard" with > your voltage sources (Trise=1ns, Ri=0Ohm). [quoted text clipped - 24 lines] > > .END >> Hello, >> [quoted text clipped - 8 lines] > > Most likely you saw 12V spikes. Hello We talked about a spike with 4V on top of the 12V DC. Best regards, Helmut PS: The rectifier has two 120A diodes 120NQ045. http://www.datasheetcatalog.com/datasheets_pdf/1/2/0/N/120NQ045.shtml > On Mar 14, 3:00 pm, "Helmut Sennewald" <helmutsennew...@t-online.de> > wrote: [quoted text clipped - 63 lines] > > .END Hello, When I look into your circuit, it seems a little bit unpractical: You are using power diodes in combination with ps pulses. You might reduce the rise and fall times of your sources and add a load resistor (to ground for example). When the load resistance is not in the many Meg Ohms, you might reduce the GMIN parameter (it will probably default in the 1e-12 range). This may help to converge the simulation process. Pspice reduces its time step until the specified accuracy is reached (with a certain minimum time step). When the iterative process does not converge, you get the minimum time step error. Probably you will add inductances in the future. Inductances in combination with diodes are the key ingredients for convergence problems. Using realistic components by adding loss resistances and capacitances to inductors, helps to speed up your simulations. Hope this helps a bit. Best regards, Wim PA3DJS www.tetech.nl remove abc from the mail address. On 15 mar, 22:10, wimabc...@tetech.nl wrote: > > On Mar 14, 3:00 pm, "Helmut Sennewald" <helmutsennew...@t-online.de> > > wrote: [quoted text clipped - 73 lines] > Meg Ohms, you might reduce the GMIN parameter (it will probably > default in the 1e-12 range). Small error, you should increase it (for example from 1e-12 to 1e-9). > This may help to converge the simulation process. Pspice reduces its > time step until the specified accuracy is reached (with a certain [quoted text clipped - 13 lines] > PA3DJSwww.tetech.nl > remove abc from the mail address. best regards, Wim >On Mar 14, 3:00 pm, "Helmut Sennewald" <helmutsennew...@t-online.de> >wrote: [quoted text clipped - 63 lines] > >.END I see no load device. What is up with the picosecond edges on V_V2? > I have a couple issues I'm having trouble with, I'm using orcad 16 and > trying to simulate a simple circuit, it's basically two pulse [quoted text clipped - 19 lines] > Much thanks > J. Do you want access to China's massive pool of electronic manufacturers... but lack the time to contact suppliers, negotiate contracts, arrange shipping or monitor product quality? Don't worry - Let seriouswholesale deal with all that for you. *Check out the huge range of Gadgets, MP3 / MP4 Players, Car DVD / Audio, and Computer Accessories now by visiting the online wholesale catalog at seriouswholesale. com You'll have peace of mind thanks to the seriouswholesale Quality Control, 12-month Warranty on all products, and easy secure payment by credit card through Paypal. Selling on eBay or your own online store? Send products direct from our warehouse to your customers using our unique drop-shipping service. You can profit by selling hundreds of different products, without holding any of your own inventory! Any questions you have will be answered by the seriouswholesale English-speaking customer support team... Their aim is to make your China electronics importing business easier to run than ever before. Welcome to http://www.seriouswholesale.com. seriouswholesale - Buy from the source, profit without the hassle. - 12 Months Warranty - No minimum order restrictions - Drop-shipping with no additional fee - Pay by safely by PayPal seriouswholesale Wholesale Co., Ltd.: Chinas original and best online electronics wholesaler & drop-shipper: seriouswholesale. com > I have a couple issues I'm having trouble with, I'm using orcad 16 and > trying to simulate a simple circuit, it's basically two pulse [quoted text clipped - 19 lines] > Much thanks > J. Do you want access to China's massive pool of electronic manufacturers... but lack the time to contact suppliers, negotiate contracts, arrange shipping or monitor product quality? Don't worry - Let seriouswholesale deal with all that for you. *Check out the huge range of Gadgets, MP3 / MP4 Players, Car DVD / Audio, and Computer Accessories now by visiting the online wholesale catalog at seriouswholesale. com You'll have peace of mind thanks to the seriouswholesale Quality Control, 12-month Warranty on all products, and easy secure payment by credit card through Paypal. Selling on eBay or your own online store? Send products direct from our warehouse to your customers using our unique drop-shipping service. You can profit by selling hundreds of different products, without holding any of your own inventory! Any questions you have will be answered by the seriouswholesale English-speaking customer support team... Their aim is to make your China electronics importing business easier to run than ever before. Welcome to http://www.seriouswholesale.com. seriouswholesale - Buy from the source, profit without the hassle. - 12 Months Warranty - No minimum order restrictions - Drop-shipping with no additional fee - Pay by safely by PayPal seriouswholesale Wholesale Co., Ltd.: Chinas original and best online electronics wholesaler & drop-shipper: seriouswholesale. com > I have a couple issues I'm having trouble with, I'm using orcad 16 and > trying to simulate a simple circuit, it's basically two pulse [quoted text clipped - 19 lines] > Much thanks > J. Do you want access to China's massive pool of electronic manufacturers... but lack the time to contact suppliers, negotiate contracts, arrange shipping or monitor product quality? Don't worry - Let seriouswholesale deal with all that for you. *Check out the huge range of Gadgets, MP3 / MP4 Players, Car DVD / Audio, and Computer Accessories now by visiting the online wholesale catalog at seriouswholesale. com You'll have peace of mind thanks to the seriouswholesale Quality Control, 12-month Warranty on all products, and easy secure payment by credit card through Paypal. Selling on eBay or your own online store? Send products direct from our warehouse to your customers using our unique drop-shipping service. You can profit by selling hundreds of different products, without holding any of your own inventory! Any questions you have will be answered by the seriouswholesale English-speaking customer support team... Their aim is to make your China electronics importing business easier to run than ever before. Welcome to http://www.seriouswholesale.com. seriouswholesale - Buy from the source, profit without the hassle. - 12 Months Warranty - No minimum order restrictions - Drop-shipping with no additional fee - Pay by safely by PayPal seriouswholesale Wholesale Co., Ltd.: Chinas original and best online electronics wholesaler & drop-shipper: seriouswholesale. com |
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