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netlist: Make sure diodes step enough ... [Couriersud]

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Long story: The diode model uses log-stepping as proposed in "Circuit
Simulation" (Farid N. Najm) page 183. If the previous voltage was
sufficiently negative the new voltage after a log step could not have
increased enough to alter matrix and rhs vector.
This bug surfaced in stuntcyc video signal mixing which uses a diode for
the composite signal.
This commit is contained in:
couriersud 2020-01-15 21:09:04 +01:00
parent cf24b97012
commit e13f1516fc
1 changed files with 9 additions and 6 deletions
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15
src/lib/netlist/analog/nld_generic_models.h
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@ -153,16 +153,19 @@ namespace analog
void update_diode(nl_fptype nVd) noexcept
{
nl_fptype IseVDVt(nlconst::zero());
if (TYPE == diode_e::BIPOLAR)
{
//printf("%s: %g %g\n", m_name.c_str(), nVd, (nl_fptype) m_Vd);
if (nVd > m_Vcrit)
{
const nl_fptype d = std::min(+fp_constants<nl_fptype>::DIODE_MAXDIFF(), nVd - m_Vd);
// if the old voltage is less than zero and new is above
// make sure we move enough so that matrix and current
// changes.
const nl_fptype old = std::max(nlconst::zero(), m_Vd());
const nl_fptype d = std::min(+fp_constants<nl_fptype>::DIODE_MAXDIFF(), nVd - old);
const nl_fptype a = plib::abs(d) * m_VtInv;
m_Vd = m_Vd + nlconst::magic(d < 0 ? -1.0 : 1.0) * plib::log1p(a) * m_Vt;
m_Vd = old + nlconst::magic(d < 0 ? -1.0 : 1.0) * plib::log1p(a) * m_Vt;
//printf("new VD: %g\n", (nl_fptype)m_Vd);
}
else
m_Vd = std::max(-fp_constants<nl_fptype>::DIODE_MAXDIFF(), nVd);
@ -175,7 +178,7 @@ namespace analog
}
else
{
IseVDVt = plib::exp(m_logIs + m_Vd * m_VtInv);
const auto IseVDVt = plib::exp(m_logIs + m_Vd * m_VtInv);
m_Id = IseVDVt - m_Is;
m_G = IseVDVt * m_VtInv + m_gmin;
}
@ -191,7 +194,7 @@ namespace analog
else // log stepping should already be done in mosfet
{
m_Vd = nVd;
IseVDVt = plib::exp(std::min(+fp_constants<nl_fptype>::DIODE_MAXVOLT(), m_logIs + m_Vd * m_VtInv));
const auto IseVDVt = plib::exp(std::min(+fp_constants<nl_fptype>::DIODE_MAXVOLT(), m_logIs + m_Vd * m_VtInv));
m_Id = IseVDVt - m_Is;
m_G = IseVDVt * m_VtInv + m_gmin;
}