Some update to SOA for a diode:
Limit output to four digits Add power and temperature limits. Derating with self-heating, or with fixed temperature, or no derating at all, selectable by setting model parameters. Example file: SOA plotted as frame, with diode current.
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Holger Vogt
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33571877dc
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SOA test for generic diode, including self-heating
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* forward direction
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* ngspice-35
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*.temp 200
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vtamb tamb 0 27
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v1 1 0 0.7
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R1 1 0 100 ; just a parallel resistor
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D1 1 0 tj dmod thermal
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Rtj tj tamb 100 ; the thermal resistance junction to ambient
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* diode model parameters include all SOA parameters
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.model dmod d (rs=200m bv=21 rth0=1e6 tnom=25 fv_max=1.5 bv_max=20 id_max=1.5 pd_max=1 te_max=175)
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.option warn=1 maxwarns=2
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.control
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save @d1[id] all
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*dc v1 3 -22.5 -0.5
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dc v1 0.02 2 0.02
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*display
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set xbrushwidth=3
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* get data from diode model
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let pdmax = @dmod[pd_max]
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let idmax = @dmod[id_max]
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let vmax = @dmod[fv_max]
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let tmax = @dmod[te_max]
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let tnom = @dmod[tnom]
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let iid = @d1[id]
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let ilen = length(iid)
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let soa = unitvec(ilen) * idmax
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* the current power dissipation in the diode
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let pd=@d1[id]*v(1) + 1p ; 1p for log scale, avoid 0
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* plot the static SOA diagram
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* no self heating
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let i = 0
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while i < ilen
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* power limit
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let pp = soa[i] * v(1)[i]
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if pp > pdmax
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let soa[i] = soa[i] * pdmax / pp
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end
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* voltage limit
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if v(1)[i] > vmax
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let soa[i] = 1p
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end
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* temperature limit
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let tcur = pp * @Rtj[r] + v(tamb)
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if tcur[i] > tmax
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let soa[i] = 1p
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end
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let i = i + 1
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end
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settype current iid soa
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plot iid soa loglog ylimit 10m 10 xlimit 0.1 1 title 'Diode SOA (safe operating area, no self-heating)' ylabel 'Diode current' xlabel 'Diode forward voltage'
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unlet pdmax
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let pdmax = @dmod[pd_max] - (v(tj) - tnom) / @Rtj[r]
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let tdio = v(tj)
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echo
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*echo pdmax $&pdmax
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*echo temp $&tdio
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*echo tnom $&tnom
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echo
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let plen = length(pdmax)
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let i = 0
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while i < plen
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if pdmax[i] < 0
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let pdmax[i] = 1p
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end
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let i = i + 1
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end
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* plot the static SOA diagram
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* now with self heating
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let i = 0
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while i < ilen
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* power limit
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let pp = soa[i] * v(1)[i]
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if pp > pdmax[i]
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let soa[i] = soa[i] * pdmax[i] / pp
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end
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* voltage limit
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if v(1)[i] > vmax
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let soa[i] = 1p
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end
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* temperature limit
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let tcur = pp * @Rtj[r] + v(tamb)
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if tcur[i] > tmax
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let soa[i] = 1p
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end
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let i = i + 1
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end
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settype current iid soa
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plot iid soa loglog ylimit 10m 10 xlimit 0.1 1 title 'Diode SOA (safe operating area, including self-heating)' ylabel 'Diode current' xlabel 'Diode forward voltage'
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*settype power pd pdmax
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*plot pd pdmax loglog ylimit 1m 10 xlimit 0.1 1
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*settype temperature tj
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*plot tj
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*plot pd vs tj pdmax vs tj
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.endc
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.end
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@ -20,6 +20,7 @@ DIOsoaCheck(CKTcircuit *ckt, GENmodel *inModel)
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double vd; /* current diode voltage */
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double id; /* current diode current */
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double pd; /* current diode power */
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double pd_max; /* maximum diode power */
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double te; /* current diode temperature */
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int maxwarns;
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static int warns_fv = 0, warns_bv = 0, warns_id = 0, warns_pd = 0, warns_te = 0;
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@ -45,7 +46,7 @@ DIOsoaCheck(CKTcircuit *ckt, GENmodel *inModel)
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if (vd > model->DIOfv_max)
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if (warns_fv < maxwarns) {
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soa_printf(ckt, (GENinstance*) here,
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"Vd=%g V has exceeded Fv_max=%g V\n",
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"Vd=%.4g V has exceeded Fv_max=%.4g V\n",
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vd, model->DIOfv_max);
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warns_fv++;
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}
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@ -53,7 +54,7 @@ DIOsoaCheck(CKTcircuit *ckt, GENmodel *inModel)
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if (-vd > model->DIObv_max)
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if (warns_bv < maxwarns) {
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soa_printf(ckt, (GENinstance*) here,
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"Vd=%g V has exceeded Bv_max=%g V\n",
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"Vd=%.4g V has exceeded Bv_max=%.4g V\n",
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vd, model->DIObv_max);
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warns_bv++;
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}
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@ -62,7 +63,7 @@ DIOsoaCheck(CKTcircuit *ckt, GENmodel *inModel)
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if (id > fabs(model->DIOid_max))
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if (warns_id < maxwarns) {
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soa_printf(ckt, (GENinstance*) here,
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"Id=%g A at Vd=%g V has exceeded Id_max=%g A\n",
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"Id=%.4g A at Vd=%.4g V has exceeded Id_max=%.4g A\n",
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id, vd, model->DIOid_max);
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warns_id++;
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}
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@ -72,25 +73,65 @@ DIOsoaCheck(CKTcircuit *ckt, GENmodel *inModel)
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*(ckt->CKTstate0 + here->DIOvoltage) +
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*(ckt->CKTstate0 + here->DIOcurrent) *
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*(ckt->CKTstate0 + here->DIOcurrent) / here->DIOtConductance);
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if (pd > fabs(model->DIOpd_max))
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if (warns_pd < maxwarns) {
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soa_printf(ckt, (GENinstance*) here,
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"Pd=%g W at Vd=%g V has exceeded Pd_max=%g W\n",
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pd, vd, model->DIOpd_max);
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warns_pd++;
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}
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te = here->DIOtemp - CONSTCtoK;
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if (te > model->DIOte_max)
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if (warns_te < maxwarns) {
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soa_printf(ckt, (GENinstance*) here,
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"Te=%g C at Vd=%g V has exceeded te_max=%g C\n",
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te, vd, model->DIOte_max);
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warns_te++;
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/* calculate max power including derating:
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up to tnom the derating is zero,
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at maximum temp allowed the derating is 100%.
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Device temperature by self-heating or given externally. */
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if (here->DIOthermal && model->DIOrth0Given && model->DIOpd_maxGiven
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&& model->DIOte_maxGiven && model->DIOnomTempGiven) {
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te = ckt->CKTrhsOld[here->DIOtempNode];
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if (te < model->DIOnomTemp)
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pd_max = model->DIOpd_max;
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else {
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pd_max = model->DIOpd_max - (te - model->DIOnomTemp) / model->DIOrth0;
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pd_max = (pd_max > 0) ? pd_max : 0.;
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}
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if (pd > pd_max)
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if (warns_pd < maxwarns) {
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soa_printf(ckt, (GENinstance*)here,
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"Pd=%.4g W at Vd=%.4g V and Te=%.4g C has exceeded Pd_max=%.4g W\n",
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pd, vd, te, pd_max);
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warns_pd++;
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}
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if (te > model->DIOte_max)
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if (warns_te < maxwarns) {
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soa_printf(ckt, (GENinstance*)here,
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"Te=%.4g C at Vd=%.4g V has exceeded te_max=%.4g C\n",
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te, vd, model->DIOte_max);
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warns_te++;
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}
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}
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/* derating without self-heating, external temp given */
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else if (!here->DIOthermal && here->DIOtempGiven && model->DIOrth0Given && model->DIOpd_maxGiven
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&& model->DIOte_maxGiven && model->DIOnomTempGiven) {
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if (here->DIOtemp < model->DIOnomTemp)
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pd_max = model->DIOpd_max;
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else {
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pd_max = model->DIOpd_max - (here->DIOtemp - model->DIOnomTemp) / model->DIOrth0;
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pd_max = (pd_max > 0) ? pd_max : 0.;
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}
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if (pd > pd_max)
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if (warns_pd < maxwarns) {
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soa_printf(ckt, (GENinstance*)here,
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"Pd=%.4g W at Vd=%.4g V and Te=%.4g C has exceeded Pd_max=%.4g W\n",
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pd, vd, here->DIOtemp - CONSTCtoK, pd_max);
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warns_pd++;
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}
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}
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/* no derating */
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else {
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pd_max = model->DIOpd_max;
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if (pd > pd_max)
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if (warns_pd < maxwarns) {
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soa_printf(ckt, (GENinstance*)here,
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"Pd=%.4g W at Vd=%.4g V has exceeded Pd_max=%.4g W\n",
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pd, vd, pd_max);
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warns_pd++;
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}
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}
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}
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}
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return OK;
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