Ideal diode

Piecewise-linear diode: Ron when conducting, Goff when blocking.

  • electrical
  • Modelica Standard Library
  • 2 ports
  • 3 parameters
BlockIdeal diodeKindidealDiodeLibrarySemiconductors

Description

A piecewise-linear diode: a small resistance Ron when conducting, a small conductance Goff when blocking. It switches at the knee point v = Vknee with no smooth transition.

Use it for rectifiers and freewheeling paths where the exact forward curve does not matter.

Example

Diodes and a Zener regulator Three diode models rectifying a 10 V sine, and a Zener diode holding 5.1 V.

10 V 50 Hz ADiodeLoad Av AGround A10 V 50 Hz BIdeal diodeLoad Bv BGround B10 V 50 Hz CDiode (exponential)Load Cv CGround C12 VR 100 ΩZener 5.1 Vv ZenerGround (Zener)
In Gradara, select a Ideal diode block and press F1, then choose Open example. It opens as a new model in My models, ready to run.

Also in this example:DC voltageVoltage sensorGroundResistorDiodeAC voltageDiode (exponential)Zener diode

Ports

Conserving terminals 2

  • +pelectrical

    Anode. Current into p is counted as positive (forward).

  • −nelectrical

    Cathode.

Parameters

  • On resistanceRon0.00001 Ω

    ≥ 0

    On resistance, in ohms: the slope of the conducting branch. 0 or more; the default 10 µΩ is near-ideal.

  • Off conductanceGoff0.00001 S

    ≥ 0

    Off conductance, in siemens: the slope of the blocking branch, so the leakage is Goff · v. 0 or more; the default 10 µS leaks 10 µA per volt.

  • Knee voltageVknee0 V

    ≥ 0

    Forward threshold voltage, in volts. 0 or more; the diode conducts once v exceeds it.

Equations

Modelica
v = p.v − n.v, i = p.i
Blocking (v < Vknee): i = Goff · v
Conducting: v = Vknee + Ron · (i − Goff · Vknee)

Implementation

Modelica Standard Library 4.1.0Modelica.Electrical.Analog.Ideal.IdealDiode
MSL documentation

Assumptions and limitations

  • No reverse recovery, junction capacitance, or reverse breakdown.
  • Each change of state is an event; many diodes switching at high frequency slow the simulation.

Tips

  • Set Vknee to about 0.7 V for a silicon forward drop, or use Diode (exponential) for the smooth curve.

Used in

These larger examples use it too. Open them from Examples in the app.

  • 480 VAC → 24 VDC flyback

See also

Select a block in Gradara and press F1 to open its page offline.