Re: New convergence failure (was Re: [Help-gnucap] Several problems: convergence failure...)

[Rubén Gómez Antolí]

Hello:

Sorry for delay in answer, I can't put my fingers on this for two weeks.

al davis escribió:
> On Sunday 07 March 2010, Rubén Gómez Antolí wrote:
> > open circuit: internal node 15
> > open circuit: internal node 20
>
> Open circuit really means a singular matrix, but from a user's 
> perspective it means a node that is being calculated in effect 
> has no connections.  Really, there are connections but they are 
> in effect open, for example a mosfet it cut-off.  Consider a 
> classic CMOS inverter.  When both devices are off, that node is 
> "open".  Often it doesn't cause a problem, but when it does you 
> can usually fix it by putting a load on the node (why I 
> suggested resistors across diodes) or making option "gmin" 
> larger (closer to zero).
>
> If you make "gmin" (for example) 1 ohm, it should converge very 
> quickly to a very wrong result.  The default value (1p, 1e-12) 
> is appropriate for small signal circuits.  It is not a good 
> value for power electronics.  Setting it to 1e-6 puts a 1 megohm 
> resistor to ground at every node.  This is probably an 
> appropriate value for power circuits.

Setting gmin to 1u, makes Gnucap runs simulate too slow, with a time 
simulation of an hour or more, and finally stop with a non-recoverable 
convergence failure:

gnucap> option gmin 1u
gnucap> print tran v(*) i(l1)
gnucap> tran 0 15ms 0.1us > Salida_opcion_gmin_1u.dat
non-recoverable convergence failure, reducing (itl4)
newtime=2.760000e-05  rejectedtime=2.760000e-05  oldtime=2.760000e-05 
using=2.760000e-05
tried everything, still doesn't work, giving up

> > non-recoverable convergence failure, reducing (itl4)
> > newtime=8.532783e-06  rejectedtime=8.532784e-06 
> >  oldtime=8.532783e-06 using=8.532784e-06
> > tried everything, still doesn't work, giving up
>
> What is happening in your circuit at time=8.53278e-06 ?  
> Something strange is happening at that instant.  A bifurcation? 
> Something switches sharply?  Look at what happens leading up to 
> that time.

Yes, at these time, triangle wave cross zero and go possitive. This make
LM311 change his output to zero and IRF540 go to cut-off zone.

Here are the circuit simplified:

-------------------- Circuit -------------------
* Convertidor reductor CC/CC - Practica 4
* gnetlist -v -g spice-sdb -o Convertidor_CC_CC_reductor.cir
Convertidor_CC_CC_reductor.sch
*==============  Begin SPICE netlist of main design ============
* Subcircuitos
.include Macromodelos/irf540n.spi
.include Macromodelos/LM311.301.cir
*
* Fuente de entrada
Vi 60 0 5V
C1 0 50 2200uF
R1 60 50 1
*
* Mosfet como interruptor
X1 50 20 80 IRF540N
* Diodo
D1 0 80 UF4004
* Filtro
C2 0 70 47uF
L1 80 70 1mH
* Carga
RL 0 70 10
*
* Control de conmutación.
*
* CONNECTIONS:   NON-INVERTING INPUT
*                | INVERTING INPUT
*                | | POSITIVE POWER SUPPLY
*                | | |   NEGATIVE POWER SUPPLY
*                | | |   |  OPEN COLLECTOR OUTPUT
*                | | |   |  | OUTPUT GROUND
*                | | |   |  | |
X2              0 10 30 40 20 0 LM311
*
* Control de conmutación. Onda triangular
.param periodo={1/20kHz}
.param subida={periodo/2}
.param bajada={periodo/2}
VG 10 0 pulse 5 -2.5 0 {subida} {bajada} 0.1us {periodo}
* Fuentes de alimentación LM311
V1 30 0 15V
V2 0 40 15V
*Resistencia control de conmutación
R2 30 20 1K
* Modelos
.model UF4004 D (IS=0.65n n=2 TT=50n VJ=0.85 CJO=31.61p MJ=0.33 EG=1.11
BV=400 IBV=10)
.end
--------------------- End of circuit ---------------

Links to subcircuits:


http://www.physics.ohio-state.edu/~durkin/phys517/Spice/LM311.mod
http://www.irf.com/product-info/models/SPICE/irf540n.spi


> > > > Try adding a switch, with the control port across a pair
> > > > of nodes that you think are causing trouble.  Leave the
> > > > output (switched resistor) unconnected.
> > I don't understand very well this. You say that add a switch
> >  in this way?:
> >
> > Sdebug 0 100 (0 80) SW
> > and node 100 is connected to "air".
> > How helps this? Sorry, I'm a bit lost.
>
> Sort of ...  What is node 80?

Node 80 are the "output" of the Mosfet, where I think that are problem 
on circuit.

>  You need to set the threshold of 
> the switch appropriately.  I was thinking of putting a switch 
> input across each diode

Each diode of the main circuit or each diode on the all circuit 
including subcircuits?

I try with the diode of the main circuit, and control with triangle 
wave, but with inverse signal:

D1 0 80 UF4004
S1 0 80 0 10 Int
.model Int SW (VON=0.2V VOFF=-0.2V RON=0.01 ROFF=1M)

Still fails, but it can hold until second zero crossing of triangle wave.

gnucap> tran 0 15ms 0.1us > Salida_802.dat
non-recoverable convergence failure, reducing (itl4)
newtime=5.852500e-05  rejectedtime=5.852500e-05  oldtime=5.852500e-05 
using=5.852500e-05
tried everything, still doesn't work, giving up

My actual knowledge on electronics, no give me more ideas.

You can see the circuit and outputs (and, if you can undestand spanish, 
me request help with this circuit) on:

http://www.foroselectronica.es/f43/problema-diseno-convertidor-cc-cc-3059.html

Thanks so much for your patiente and effort.

Salud y Revolución.

Lobo.
--
Libertad es poder elegir en cualquier momento. Ahora yo elijo GNU/Linux,
para no atar mis manos con las cadenas del soft propietario.
---------
Desde El Ejido, en Almería, usuario registrado Linux #294013
http://www.counter.li.org