Diode

Piecewise or exponential diode

Library:
Simscape / Electrical / Semiconductors & Converters / Semiconductors

Description

The Diode block can represent either a piecewise linear diode, an exponential diode, or a diode with tabulated I-V curve.

Piecewise Linear Diode

The piecewise linear diode model is the same model as the Simscape™ > Foundation Library > Electrical > Electrical Elements > Diode block, with the addition of a fixed junction capacitance and optional charge dynamics. If the diode forward voltage exceeds the value specified in the Forward voltage parameter, the diode behaves as a linear resistor with the resistance specified in the On resistance parameter. Otherwise, the diode behaves as a linear resistor with the small conductance specified in the Off conductance parameter. Zero voltage across the diode results in zero current flowing.

Exponential Diode

The exponential diode model represents the following relationship between the diode current I and the diode voltage V:

$\begin{array}{l} I = I S \cdot (e^{\frac{q V}{N k T_{m 1}}} - 1) V > - B V \\ I = - I S \cdot (e^{\frac{- q (V + V z)}{k T_{m 1}}} - e^{\frac{q V}{N k T_{m 1}}}) V \leq - B V \end{array}$

where:

q is the elementary charge on an electron (1.602176e–19 coulombs).
k is the Boltzmann constant (1.3806503e–23 J/K).
BV is the Reverse breakdown voltage parameter value.
N is the emission coefficient.
IS is the saturation current.
T_m1 is the temperature at which the diode parameters are specified, as defined by the Measurement temperature parameter value.

When (qV / NkT_m1) > 80, the block replaces $e^{\frac{q V}{N k T_{m 1}}}$ with (qV / NkT_m1– 79)e⁸⁰, which matches the gradient of the diode current at (qV / NkT_m1) = 80 and extrapolates linearly. When (qV / NkT_m1) < –79, the block replaces $e^{\frac{q V}{N k T_{m 1}}}$ with (qV / NkT_m1+ 80)e^–79, which also matches the gradient and extrapolates linearly. Typical electrical circuits do not reach these extreme values. The block provides this linear extrapolation to help convergence when solving for the constraints during simulation.

When you select Use parameters IS and N for the Parameterization parameter, you specify the diode in terms of the Saturation current IS and Emission coefficient N parameters. When you select Use two I-V curve data points for the Parameterization parameter, you specify two voltage and current measurement points on the diode I-V curve and the block derives the IS and N values. The block then calculates IS and N as follows:

$N = ((V_{1} - V_{2}) / V_{t}) / (\log (I_{1}) - \log (I_{2}))$
$IS = (I_{1} / (\exp (V_{1} / (N V_{t})) - 1) + I_{2} / (\exp (V_{2} / (N V_{t})) - 1)) / 2$

where:

V_t = kT_m1 / q.
V₁ and V₂ are the values in the Voltages [V1 V2] vector.
I₁ and I₂ are the values in the Currents [I1 I2] vector.

When you select Use an I-V data point and IS for the Parameterization parameter, then the block calculates N as follows:

$N = V_{1} / (V_{t} \log (\frac{I_{1}}{I S} + 1))$

When you select Use an I-V data point and N for the Parameterization parameter, then the block calculates IS as follows:

$I S = I_{1} / (\exp (V_{1} / (N V_{t}) - 1))$

Tabulated Diode

To model a tabulated diode, set the Diode model parameter to Tabulated I-V curve. This figure shows the implementation of the tabulated diode option:

When choosing this parameterization, you must provide the data for the forward bias only. If the diode is reverse biased, it is modeled as a constant off-state conductance specified in the Off conductance parameter instead. The value of the Off conductance must be less than the gradient of the forward I-V curve for small positive voltages.

The block implements the diode using a smooth interpolation option. If the diode exceeds the provided tabulated data range, the block uses a linear extrapolation technique at the last voltage-current data point.

Note

The tabulated diode does not model the reverse breakdown.

Junction Capacitance

The block provides the option to include a junction capacitance:

When you select Include fixed or zero junction capacitance for the Junction capacitance parameter, the capacitance is fixed.
When you select Use parameters CJO, VJ, M & FC for the Junction capacitance parameter, the block uses the coefficients CJO, VJ, M, and FC to calculate a junction capacitance that depends on the junction voltage.
When you select Use C-V curve data points for the Junction capacitance parameter, the block uses three capacitance values on the C-V capacitance curve to estimate CJO, VJ, and M and uses these values with the specified value of FC to calculate a junction capacitance that depends on the junction voltage. The block calculates CJO, VJ, and M as follows:
- $C J 0 = C_{1} {((V_{R 2} - V_{R 1}) / (V_{R 2} - V_{R 1} {(C_{2} / C_{1})}^{- 1 / M}))}^{M}$
- $V J = - (- V_{R 2} {(C_{1} / C_{2})}^{- 1 / M} + V_{R 1}) / (1 - {(C_{1} / C_{2})}^{- 1 / M})$
- $M = \log (C_{3} / C_{2}) / \log (V_{R 2} / V_{R 3})$
where:
- V_R1, V_R2, and V_R3 are the values in the Reverse bias voltages [VR1 VR2 VR3] vector.
- C₁, C₂, and C₃ are the values in the Corresponding capacitances [C1 C2 C3] vector.
The reverse bias voltages (defined as positive values) should satisfy V_R3 > V_R2 > V_R1. This means that the capacitances should satisfy C₁ > C₂ > C₃ as reverse bias widens the depletion region and hence reduces capacitance. Violating these inequalities results in an error. Voltages V_R2 and V_R3 should be well away from the Junction potential VJ. Voltage V_R1 should be less than the Junction potential VJ, with a typical value for V_R1 being 0.1 V.

The voltage-dependent junction capacitance is defined in terms of the capacitor charge storage Q_j as:

For V < FC·VJ:

$Q_{j} = C J 0 \cdot (V J / (M - 1)) \cdot ({(1 - V / V J)}^{1 - M} - 1)$
For V ≥ FC·VJ:

$Q_{j} = C J 0 \cdot F_{1} + (C J 0 / F_{2}) \cdot (F_{3} \cdot (V - F C \cdot V J) + 0.5 (M / V J) \cdot (V^{2} - {(F C \cdot V J)}^{2}))$

where:

$F_{1} = (V J / (1 - M)) \cdot (1 - {(1 - F C)}^{1 - M}))$
$F_{2} = {(1 - F C)}^{1 + M}))$
$F_{3} = 1 - F C \cdot (1 + M)$

These equations are the same as used in [2], except that the temperature dependence of VJ and FC is not modeled.

Charge Dynamics

For applications such as commutation diodes it can be important to model diode charge dynamics. When a forward-biased diode has a reverse voltage applied across it, it takes time for the charge to dissipate and hence for the diode to turn off. The time taken for the diode to turn off is captured primarily by the transit time parameter. Once the diode is off, any remaining charge then dissipates, the rate at which this happens being determined by the carrier lifetime.

The Diode block uses the model of Lauritzen and Ma [3] to capture these effects. These are the defining equations.

i = \frac{q_{E} - q_{M}}{T_{M}}

(1)

\frac{d q_{M}}{d t} + \frac{q_{M}}{τ} - \frac{q_{E} - q_{M}}{T_{M}} = 0

(2)

q_{E} = (τ + T_{M}) i

(3)

where:

i is the diode current.
q_E is the junction charge.
q_M is the total stored charge.
T_M is the transit time.
τ is the carrier lifetime.
v_D is the voltage across the diode.
v_F is the diode forward voltage.
R is the diode on resistance.
G is the diode off conductance.

This graphic shows a typical reverse-mode current characteristic for a diode device.

where:

i_RM is the peak reverse current.
i_F is the starting forward current when measuring i_RM.
a is the rate of change of current when measuring i_RM.
t_rr is the reverse recovery time.

Data sheets for diodes quote values for peak reverse current for an initial forward current and a steady rate of change of current. The data sheet might also provide values for reverse recovery time and total recovery charge.

How the Block Calculates T_M and Tau

The block calculates transit time T_M and carrier lifetime τ based on the values you enter for the Charge Dynamics parameters. The block uses T_M and τ to solve the charge dynamics equations 1, 2, and 3.

During initial current drop in reverse mode, the diode is still on, and the rate of change of current is determined by an external test circuit.

First, the block uses equation 1 to perform this calculation.

i_{F} + a t = \frac{q_{E} - q_{M}}{T_{M}}

(4)

Then, it substitutes equation 4 into equation 2.

\frac{d q_{M}}{d t} + \frac{q_{M}}{τ} = i_{F} + a t

(5)

Then, it solves equation 5 for q_M,

q_{M} = i_{F} τ - a τ^{2} + \frac{k}{\exp (\frac{t}{τ})} + a τ t,

(6)

where k is a constant.

When t is zero, i = i_F and q_M = τi_F because the system is in steady state.

Substituting these relationships into equation 6 and solving the equation gives k = aτ².

Therefore,

q_{M} = i_{F} τ + a τ^{2} (\frac{1}{\exp (\frac{t}{τ})} - 1) + a τ t .

(7)

At time t = t_s, the current is i_RM and the junction charge q_E is zero.

The block substitutes these values into equation 1.

i_{R M} = \frac{- q_{M}}{T_{M}}

(8)

The block rearranges equation 8 to solve for q_M and substitutes the result into equation 7.

- T_{M} i_{R M} = i_{F} τ + a τ^{2} (\frac{1}{\exp (\frac{t_{s}}{τ})} - 1) + a τ t_{s}

(9)

Then, the block expresses time t_s in terms of i_RM, i_F, and a.

t_{s} = \frac{i_{R M} - i_{F}}{a}

(10)

Consider the diode recovery, that is, when t > t_s. The diode is reverse biased, and current and junction charge are effectively zero.

The current is defined by this equation.

i = i_{R M} exp[\frac{- (t - t_{s})}{τ_{r r}}],

(11)

where:

\frac{1}{τ_{r r}} = \frac{1}{τ} + \frac{1}{T_{M}} .

(12)

The block now relates the expression in equation 12 to the reverse recovery time t_rr.

When $t = \frac{i_{R M}}{a} + t_{r r},$ the current is $\frac{i_{R M}}{10} .$

Therefore,

\exp (- \frac{t - t_{s}}{τ_{r r}}) = 0.1

(13)

and

t_{r r} = τ_{r r} \log (10) + \frac{i_{R M}}{a} .

(14)

The block uses equations 9 and 14 to calculate values for T_M and τ. The calculation uses an iterative scheme because of the exponential term in Equation 9.

Alternatives to Specifying t_rr Directly

In addition to allowing you to specify reverse recovery time t_rr directly, the block supports two alternative parameterizations. The block can derive t_rr from either of these parameters:

Reverse recovery time stretch factor λ
Reverse recovery charge Q_rr, when the data sheet specifies this value instead of the reverse recovery time.

The relationship between reverse recovery time stretch factor λ and t_rr is expressed by the equation

$λ = \frac{t_{r r} a}{i_{R M}} .$

Reverse recovery time must be greater than $\frac{i_{R M}}{a}$ and a typical value is $3 (\frac{i_{R M}}{a}) .$

Therefore, a typical value for λ is 3. λ must be greater than 1.

Reverse recovery charge Q_rr is the integral over time of the reverse current from the point where the current goes negative until it decays back to zero.

The initial charge, to time t_s (as shown in the figure), is expressed by this equation:

Q_{s} = \frac{1}{2} (- i_{R M}) \frac{i_{R M}}{a} .

(15)

Integrating equation 11 gives the charge between times t_s and inf. This charge is equal to

$τ_{r r} i_{R M} .$

Therefore, total reverse recovery charge is given by this equation:

Q_{r r} = - \frac{i_{R M}^{2}}{2 a} + τ_{r r} i_{R M} .

(16)

Rearranging equation 16 to solve for τ_rr and substituting the result into equation 14 gives an equation that expresses t_rr in terms of Q_rr:

$t_{r r} = (\frac{Q_{r r}}{i_{R M}} + \frac{i_{R M}}{2 a}) \log (10) + \frac{i_{R M}}{a} .$

Temperature Dependence

The default behavior for the Diode block is that dependence on temperature is not modeled, and the device is simulated at the temperature for which you provide block parameters. The exponential diode model contains several options for modeling the dependence of the diode current-voltage relationship on temperature during simulation. Temperature dependence of the junction capacitance is not modeled because it has a much smaller effect.

When including temperature dependence, the diode defining equation remains the same. The measurement temperature value, T_m1, is replaced with the simulation temperature, T_s. The saturation current, IS, becomes a function of temperature according to the following equation:

$I S_{T s} = I S_{T m 1} \cdot {(T_{s} / T_{m 1})}^{X T I / N} \cdot \exp (- \frac{E G}{N k T_{s}} (1 - T_{s} / T_{m 1}))$

where:

T_m1 is the temperature at which the diode parameters are specified, as defined by the Measurement temperature parameter value.
T_s is the simulation temperature.
IS_Tm1 is the saturation current at measurement temperature.
IS_Ts is the saturation current at simulation temperature. This is the saturation current value used in the standard diode equation when temperature dependence is modeled.
EG is the energy gap for the semiconductor type measured in joules(J). The value for silicon is usually taken to be 1.11 eV, where 1 eV is 1.602e-19.
XTI is the saturation current temperature exponent. This is usually set to 3.0 for pn-junction diodes, and 2.0 for Schottky barrier diodes.
N is the emission coefficient.
k is the Boltzmann constant (1.3806503e–23 J/K).

Appropriate values for XTI and EG depend on the type of diode and the semiconductor material used. Default values for particular material types and diode types capture approximate behavior with temperature. The block provides default values for common types of diode.

In practice, the values of XTI and EG need tuning to model the exact behavior of a particular diode. Some manufacturers quote these tuned values in a SPICE Netlist, and you can read off the appropriate values. Otherwise, you can determine improved estimates for EG by using a datasheet-defined current-voltage data point at a higher temperature. The block provides a parameterization option for this. It also gives the option of specifying the saturation current at a higher temperature IS_Tm2 directly.

You can also tune the values of XTI and EG yourself, to match lab data for your particular device. You can use Simulink^® Design Optimization™ software to help tune the values for XTI and EG.

Caution

Device temperature behavior is also dependent on the emission coefficient. An inappropriate value for the emission coefficient can give incorrect temperature dependence, because saturation current is a function of the ratio of EG to N.

If defining a finite reverse breakdown voltage (BV), then the value of the reverse BV is modulated by the reverse breakdown temperature coefficient TCV (specified using the Reverse breakdown voltage temperature coefficient, dBV/dT parameter):

BV_Ts = BV_Tm1 – TCV· (T_s – T_m1)

(17)

Modeling Variants

The block provides a thermal modeling variant. To select a variant, right-click the block in your model. From the context menu, select Simscape > Block choices, and then one of these variants:

No thermal port — This variant does not simulate heat generation in the device. This variant is the default.
Show thermal port — This variant contains a thermal port that allows you to model the heat that conduction losses generate. For numerical efficiency, the thermal state does not affect the electrical behavior of the block. The thermal port is hidden by default. When you select a thermal variant of the block, the thermal port appears.

Thermal Port

The block has an optional thermal port, hidden by default. To expose the thermal port, right-click the block in your model, and then from the context menu select Simscape > Block choices > Show thermal port. This action displays the thermal port H on the block icon, and exposes the Thermal Port parameters.

Use the thermal port to simulate the effects of generated heat and device temperature. For more information on using thermal ports and on the Thermal Port parameters, see Simulating Thermal Effects in Semiconductors.

Variables

Use the Variables section of the block interface to set the priority and initial target values for the block variables prior to simulation. For more information, see Set Priority and Initial Target for Block Variables.

Assumptions and Limitations

When you select Use two I-V curve data points for the Parameterization parameter, choose a pair of voltages near the diode turn-on voltage. Typically, this is in the range from 0.05 to 1 V. Using values outside of this region may lead to numerical issues and poor estimates for IS and N.
The block does not account for temperature-dependent effects on the junction capacitance.
You may need to use nonzero ohmic resistance and junction capacitance values to prevent numerical simulation issues, but the simulation may run faster with these values set to zero.
You cannot use the Tabulated I-V curve parameterization to model the reverse breakdown.

Ports

Conserving

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`+` — Positive terminal
electrical

Electrical conserving port associated with the anode.

`-` — Negative terminal
electrical

Electrical conserving port associated with the cathode.

`H` — Thermal port
thermal

Thermal conserving port. The thermal port is optional and is hidden by default. To enable this port, select a variant that includes a thermal port.

Parameters

expand all

Main

`Diode model` — Diode model
`Piecewise Linear` (default) | `Exponential` | `Tabulated I-V curve`

Select one of these diode models:

Piecewise Linear — Use a piecewise linear model for the diode, as described in Piecewise Linear Diode. This is the default method.
Exponential — Use a standard exponential model for the diode, as described in Exponential Diode.
Tabulated I-V curve — Use tabulated forward bias I-V data plus fixed reverse bias off conductance, as described in Tabulated Diode.

`Forward voltage` — Forward voltage
`0.6` `V` (default)

Minimum voltage that needs to be applied for the diode to become forward-biased.

Dependencies

To enable this parameter, set Diode model to Piecewise linear.

`On resistance` — On resistance
`0.3` `Ohm` (default)

Resistance of the diode when it is forward biased.

Dependencies

To enable this parameter, set Diode model to Piecewise linear.

`Off conductance` — Off conductance
`1e-8` `1/Ohm` (default)

Conductance of the diode when it is reverse biased.

Dependencies

To enable this parameter, set Diode model to Piecewise linear or Tabulated I-V curve.

`Parameterization` — Model parameterization
`Use two I-V curve data points` (default) | `Use parameters IS and N` | `Use an I-V data point and IS` | `Use an I-V data point and N`

Select one of the following methods for model parameterization:

Use two I-V curve data points — Specify measured data at two points on the diode I-V curve. This is the default method.
Use parameters IS and N — Specify saturation current and emission coefficient.
Use an I-V data point and IS — Specify measured data at a single point on the diode I-V curve in combination with the saturation current.
Use an I-V data point and N — Specify measured data at a single point on the diode I-V curve in combination with the emission coefficient.

Dependencies

To enable this parameter, set Diode model to Exponential.

`Currents [I1 I2]` — Vector of current values at two points
`[.0137, .545]` `A` (default)

Vector of the current values at the two points on the diode I-V curve that the block uses to calculate IS and N.

Dependencies

To enable this parameter, set Diode model to Exponential and Parameterization to Use two I-V curve data points.

`Voltages [V1 V2]` — Vector of voltage values at two points
`[.6, .7]` `V` (default)

Vector of the voltage values at the two points on the diode I-V curve that the block uses to calculate IS and N.

Dependencies

To enable this parameter, set Diode model to Exponential and Parameterization to Use two I-V curve data points.

`Saturation current, IS` — Saturation current
`1e-12` `A` (default)

Magnitude of the current that the ideal diode equation approaches asymptotically for very large reverse bias levels.

Dependencies

To enable this parameter, set Diode model to Exponential and Parameterization to Use parameters IS and N or Use an I-V data point and IS.

`Emission coefficient, N` — Diode emission coefficient
`1` (default)

Diode emission coefficient or ideality factor.

Dependencies

To enable this parameter, set Diode model to Exponential and Parameterization to Use parameters IS and N or Use an I-V data point and IS.

`Current I1` — Current value
`0.0137` `A` (default)

Current value at the point on the diode I-V curve that the block uses for calculations. Depending on the Parameterization value, the block uses this parameter to calculate either N or IS.

Dependencies

To enable this parameter, set Diode model to Exponential and Parameterization to Use an I-V data point and IS or Use an I-V data point and N.

`Voltage V1` — Voltage value
`0.6` `V` (default)

Voltage value at the point on the diode I-V curve that the block uses for calculations.

Dependencies

To enable this parameter, set Diode model to Exponential and Parameterization to Use an I-V data point and IS or Use an I-V data point and N.

`Ohmic resistance, RS` — Ohmic resistance
`0` `Ohm` (default)

Series diode connection resistance.

Dependencies

To enable this parameter, set Diode model to Exponential.

`Measurement temperature` — Measurement temperature
`25` `degC` (default)

Temperature T_m1 at which IS or the I-V curve was measured.

`Forward currents, If(Tj,Vf)` — Vector of forward currents
`[.07, .12, .19, 1.75, 4.24, 7.32, 11.2; .16, .3, .72, 2.14, 4.02, 6.35, 9.12]` `A` (default) | nonnegative vector

Forward currents. This parameter must be a vector of at least three nonnegative elements.

Dependencies

To enable this parameter, set Diode model to Tabulated I-V curve.

`Junction temperatures, Tj` — Vector of junction temperatures
`[25, 125]` `degC` (default)

Vector of junction temperatures. This parameter must be a vector of at least two elements.

Dependencies

To enable this parameter, set Diode model to Tabulated I-V curve.

`Forward voltages, Vf` — Vector of forward voltages
`[.5, .7, .9, 1.3, 1.7, 2.1, 2.5]` `V` (default)

Vector of forward voltages. This parameter must be a vector of at least three nonnegative values.

Dependencies

To enable this parameter, set Diode model to Tabulated I-V curve.

`Number of series diodes` — Number of diodes connected in series
`1` (default)

Number of diodes connected in series between the + and – block ports. Multiple diodes are not modeled. Rather, each diode has all voltage-related quantities scaled by the factor that you specify.

`Number of parallel diodes` — Number of parallel diodes
`1` (default)

Number of parallel diodes, or number of parallel paths formed by series-connected diodes, between the + and – block ports. Multiple diodes are not modeled. Rather, each diode has all current-related quantities scaled by the factor that you specify.

Breakdown

`Zener resistance` — Zener resistance
`0.3` `Ohm` (default)

Resistance of the diode when the voltage is less than the Reverse breakdown voltage value.

Dependencies

To enable this parameter, set Diode model to Piecewise linear.

`Reverse breakdown voltage` — Reverse breakdown voltage
`inf` `V` (default)

Reverse voltage below which to model the rapid increase in conductance that occurs at diode breakdown. The default value is Inf V, which effectively omits reverse breakdown from the model.

Capacitance

`Capacitance` — Modeling junction capacitance
`Fixed or zero junction capacitance` (default) | `Use C-V curve data points` | `Use parameters CJ0, VJ, M & FC`

Method for modeling the junction capacitance:

Fixed or zero junction capacitance — Model the junction capacitance as a fixed value.
Use C-V curve data points — Specify measured data at three points on the diode C-V curve.
Use parameters CJ0, VJ, M & FC — Specify zero-bias junction capacitance, junction potential, grading coefficient, and forward-bias depletion capacitance coefficient.

`Junction capacitance` — Junction capacitance
`5` `pF` (default)

Fixed junction capacitance value.

Dependencies

To enable this parameter, set Capacitance to Fixed or zero junction capacitance.

`Reverse bias voltages [VR1 VR2 VR3]` — Vector of reverse bias voltage values
`[.1, 10, 100]` `V` (default)

Vector of the reverse bias voltage values at the three points on the diode C-V curve that the block uses to calculate CJ0, VJ, and M.

Dependencies

To enable this parameter, set Capacitance to Use C-V curve data points.

`Corresponding capacitances [C1 C2 C3]` — Vector of capacitance values
`[3.5, 1, .4]` `pF` (default)

Vector of the capacitance values at the three points on the diode C-V curve that the block uses to calculate CJ0, VJ, and M.

Dependencies

To enable this parameter, set Capacitance to Use C-V curve data points.

`Zero-bias junction capacitance, CJ0` — Zero-bias junction capacitance
`5` `pF` (default)

Value of the capacitance placed in parallel with the conduction current term.

Dependencies

To enable this parameter, set Capacitance to Use parameters CJ0, VJ, M & FC.

`Junction potential, VJ` — Junction potential
`1` `V` (default)

The junction potential.

Dependencies

To enable this parameter, set Capacitance to Use parameters CJ0, VJ, M & FC.

`Grading coefficient, M` — Grading coefficient
`0.5` (default)

Grading coefficient.

Dependencies

To enable this parameter, set Capacitance to Use parameters CJ0, VJ, M & FC.

`Capacitance coefficient, FC` — Capacitance coefficient
`0.5` (default)

Fitting coefficient that quantifies the decrease of the depletion capacitance with applied voltage.

Dependencies

To enable this parameter, set Capacitance to Use parameters CJ0, VJ, M & FC.

`Charge dynamics` — Charge dynamics parameterization
`Do not model charge dynamics` (default) | `Use peak reverse current and stretch factor` | `Use peak reverse current and reverse recovery time` | `Use peak reverse current and reverse recovery charge` | `Use transit time and carrier lifetime`

Select one of the following methods for charge dynamics parameterization:

Do not model charge dynamics — Do not include charge dynamics modeling. This is the default method.
Use peak reverse current and stretch factor — Model charge dynamics by providing values for peak reverse current i_RM and stretch factor λ plus information on the initial forward current and rate of change of current used in the test circuit when measuring i_RM and t_rr.
Use peak reverse current and reverse recovery time — Model charge dynamics by providing values for peak reverse current i_RM and reverse recovery time t_rr plus information on the initial forward current and rate of change of current used in the test circuit when measuring i_RM and t_rr. Use this option if the manufacturer datasheet does not provide values for transit time TT and carrier lifetime τ.
Use peak reverse current and reverse recovery charge — Model charge dynamics by providing values for peak reverse current i_RM and reverse recovery charge Qrr plus information on the initial forward current and rate of change of current used in the test circuit when measuring i_RM and t_rr.
Use transit time and carrier lifetime — Model charge dynamics by providing values for transit time TT and carrier lifetime τ.

`Peak reverse current, iRM` — Peak reverse current
`-7.15` `A` (default) | negative scalar

Peak reverse current measured by an external test circuit. This value must be less than zero.

Dependencies

To enable this parameter, set Charge dynamics to Use peak reverse current and stretch factor, Use peak reverse current and reverse recovery time, or Use peak reverse current and reverse recovery charge.

`Initial forward current when measuring iRM` — Initial forward current when measuring iRM
`4` `A` (default) | positive scalar

Initial forward current when measuring peak reverse current. This value must be greater than zero.

Dependencies

`Rate of change of current when measuring iRM` — Rate of change of current when measuring iRM
`-750` `A/μs` (default) | negative scalar

Rate of change of current when measuring peak reverse current. This value must be less than zero.

Dependencies

`Reverse recovery time stretch factor` — Reverse recovery time stretch factor
`3` (default)

Value that the block uses to calculate Reverse recovery time, trr. This value must be greater than 1. The default value is 3.

Specifying the stretch factor is an easier way to parameterize the reverse recovery time than specifying the reverse recovery charge. The larger the value of the stretch factor, the longer it takes for the reverse recovery current to dissipate.

Dependencies

To enable this parameter, set Charge dynamics to Use peak reverse current and stretch factor.

`Reverse recovery time, trr` — Reverse recovery time
`115` (default)

Time between the point where the current initially goes to zero when the diode turns off, and the point where the current falls to less than ten percent of the peak reverse current. The default value is 115 ns.

The value of the Reverse recovery time, trr parameter must be greater than the value of the Peak reverse current, iRM parameter divided by the value of the Rate of change of current when measuring iRM parameter.

Dependencies

To enable this parameter, set Charge dynamics to Use peak reverse current and reverse recovery time.

`Reverse recovery charge, Qrr` — Reverse recovery charge
`1500` `s*μA` (default)

Value that the block uses to calculate Reverse recovery time, trr. Use this parameter if the data sheet for your diode device specifies a value for the reverse recovery charge instead of a value for the reverse recovery time.

The reverse recovery charge is the total charge that continues to dissipate when the diode turns off. The value must be less than $- \frac{i^{2}_{R M}}{2 a},$

where:

i_RM is the value specified for Peak reverse current, iRM.
a is the value specified for Rate of change of current when measuring iRM.

Dependencies

To enable this parameter, set Charge dynamics to Specify reverse recovery charge.

`Transit time, TT` — Transit time
`50` `ns` (default)

Measure of how long it takes carriers to cross the diode junction.

Dependencies

To enable this parameter, set Charge dynamics to Use transit time and carrier lifetime.

`Carrier lifetime, tau` — Carrier lifetime
`100` `ns` (default)

Measure of how long it takes for the carriers to dissipate once the diode is no longer conducting. The default value is 100 ns.

Dependencies

To enable this parameter, set Charge dynamics to Use transit time and carrier lifetime.

Temperature Dependence

This section is applicable to Exponential and Tabulated I-V curve diode models only.

This table shows how the visibility of Temperature Dependence setting depends on how you configure the Diode model parameter in the Main setting and whether you expose the thermal port. To learn how to read this table, see Parameter Dependencies

Visibility of the Temperature Dependence Setting

Parameters, options, and visibility of the setting
Diode model
`Piecewise linear`		`Exponential`		`Tabulated I-V curve`
Thermal Port		Thermal Port		Thermal Port
`Not exposed`	`Exposed`	`Not exposed`	`Exposed`	`Not exposed`	`Exposed`
Hidden	Hidden	Visible	Visible	Visible	Hidden

`Parameterization` — Temperature dependence parameterization
`None - Use characteristics at parameter measurement temperature` (default) | `Use an I-V data point at second measurement temperature` | `Specify saturation current at second measurement temperature` | `Specify the energy gap EG`

Select one of the following methods for temperature dependence parameterization:

None - Use characteristics at parameter measurement temperature — Temperature dependence is not modeled, or the model is simulated at the measurement temperature T_m1 (as specified by the Measurement temperature parameter on the Main tab). This is the default method.
Use an I-V data point at second measurement temperature T2 — If you select this option, you specify a second measurement temperature T_m2, and the current and voltage values at this temperature. The model uses these values, along with the parameter values at the first measurement temperature T_m1, to calculate the energy gap value.
Specify saturation current at second measurement temperature T2 — If you select this option, you specify a second measurement temperature T_m2, and saturation current value at this temperature. The model uses these values, along with the parameter values at the first measurement temperature T_m1, to calculate the energy gap value.
Specify the energy gap EG — Specify the energy gap value directly.

`Current I1 at second measurement temperature` — Current I1 at second measurement temperature
`0.0245` `A` (default)

Specify the diode current I1 value when the voltage is V1 at the second measurement temperature.

Dependencies

To enable this parameter, set Parameterization to Use an I-V data point at second measurement temperature.

`Voltage V1 at second measurement temperature` — Voltage V1 at second measurement temperature
`0.5` `V` (default)

Specify the diode voltage V1 value when the current is I1 at the second measurement temperature.

Dependencies

To enable this parameter, set Parameterization to Use an I-V data point at second measurement temperature.

`Saturation current, IS, at second measurement temperature` — Saturation current, IS, at second measurement temperature
`1.25e-7` `A` (default)

Specify the saturation current IS value at the second measurement temperature.

Dependencies

To enable this parameter, set Parameterization to Specify saturation current at second measurement temperature.

`Second measurement temperature` — Second measurement temperature
`125` `°C` (default)

Specify the value for the second measurement temperature.

Dependencies

To enable this parameter, set Parameterization to Use an I-V data point at second measurement temperature or Specify saturation current at second measurement temperature.

`Energy gap parameterization` — Energy gap parameterization
`Use nominal value for silicon (EG=1.11eV)` (default) | `Use nominal value for 4H-SiC silicon carbide (EG=3.23eV)` | `Use nominal value for 6H-SiC silicon carbide (EG=3.00eV)` | `Use nominal value for germanium (EG=0.67eV)` | `Use nominal value for gallium arsenide (EG=1.43eV)` | `Use nominal value for selenium (EG=1.74eV)` | `Use nominal value for Schottky barrier diodes (EG=0.69eV)` | `Specify a custom value`

Select a value for the energy gap from a list of predetermined options, or specify a custom value:

Use nominal value for silicon (EG=1.11eV) — This is the default.
Use nominal value for 4H-SiC silicon carbide (EG=3.23eV)
Use nominal value for 6H-SiC silicon carbide (EG=3.00eV)
Use nominal value for germanium (EG=0.67eV)
Use nominal value for gallium arsenide (EG=1.43eV)
Use nominal value for selenium (EG=1.74eV)
Use nominal value for Schottky barrier diodes (EG=0.69eV)
Specify a custom value — If you select this option, the Energy gap, EG parameter appears in the dialog box, to let you specify a custom value for EG.

Dependencies

To enable this parameter, set Parameterization to Specify the energy gap EG.

`Energy gap, EG` — Energy gap
`1.11` `eV` (default)

Specify a custom value for the energy gap, EG.

Dependencies

To enable this parameter, set Energy gap parameterization to Specify a custom value.

`Saturation current temperature exponent parameterization` — Saturation current temperature exponent parameterization
`Use nominal value for pn-junction diode (XTI=3)` (default) | `Use nominal value for Schottky barrier diode (XTI=2)` | `Specify a custom value`

Select one of the following options to specify the saturation current temperature exponent value:

Use nominal value for pn-junction diode (XTI=3) — This is the default.
Use nominal value for Schottky barrier diode (XTI=2)
Specify a custom value — If you select this option, the Saturation current temperature exponent, XTI parameter appears in the dialog box, to let you specify a custom value for XTI.

Dependencies

`Saturation current temperature exponent, XTI` — Saturation current temperature exponent
`3` (default)

Specify a custom value for the saturation current temperature exponent, XTI.

Dependencies

To enable this parameter, set Parameterization to Use an I-V data point at second measurement temperature, Specify saturation current at second measurement temperature, or Specify the energy gap, EG and Saturation current temperature exponent parameterization to Specify a custom value.

`Reverse breakdown voltage temperature coefficient, dBV/dT` — Reverse breakdown voltage temperature coefficient
`0` `V/K` (default)

Modulate the reverse breakdown voltage BV. If you define the reverse breakdown voltage BV as a positive quantity, a positive value for TCV implies that the magnitude of the reverse breakdown voltage decreases with temperature.

Dependencies

`Device simulation temperature` — Device simulation temperature
`25` `°C` (default)

Specify the value for the temperature T_s, at which the device is to be simulated.

Dependencies

Thermal Port

Model Examples

Quantifying IGBT Thermal Losses

The generation of a temperature profile based on switching and conduction losses in an insulated-gate bipolar transistor (IGBT). There are two buck converters. For one converter, the IGBT attaches to a Foster thermal model. For the other converter, the IGBT attaches to a Cauer thermal model. The parameters for the thermal models are tuned to give roughly equivalent results. At a simulation time of 50ms, the driving frequency changes from 40kHz to 20kHz, which increases the conduction losses and decreases the switching losses. The change in the losses results in a corresponding change in the temperature of the IGBT.

Schottky Barrier Diode Characteristics

Generation of the current versus voltage curve for a Schottky barrier diode. Define the vector of temperatures for which to plot the characteristics by double clicking on the block labeled 'Define Temperatures for Tests'. Run the tests and plot the I-V curves by clicking in the model on the hyperlink 'plot curves'.

References

[1] MH. Ahmed and P.J. Spreadbury. Analogue and digital electronics for engineers. 2nd Edition. Cambridge, UK: Cambridge University Press, 1984.

[2] G. Massobrio and P. Antognetti. Semiconductor Device Modeling with SPICE. 2nd Edition. New York: McGraw-Hill, 1993.

[3] Lauritzen, P.O. and C.L. Ma. “A Simple Diode Model with Reverse Recovery.” IEEE^® Transactions on Power Electronics. Vol. 6, No. 2, April 1991, pp. 188–191.

Documentation

Diode

Description

Piecewise Linear Diode

Exponential Diode

Tabulated Diode

Junction Capacitance

Charge Dynamics

Temperature Dependence

Modeling Variants

Thermal Port

Variables

Assumptions and Limitations

Ports

Conserving

+ — Positive terminal electrical

- — Negative terminal electrical

H — Thermal port thermal

Parameters

Main

Diode model — Diode model Piecewise Linear (default) | Exponential | Tabulated I-V curve

Forward voltage — Forward voltage 0.6 V (default)

Dependencies

On resistance — On resistance 0.3 Ohm (default)

Dependencies

Off conductance — Off conductance 1e-8 1/Ohm (default)

Dependencies

Parameterization — Model parameterization Use two I-V curve data points (default) | Use parameters IS and N | Use an I-V data point and IS | Use an I-V data point and N

Dependencies

Currents [I1 I2] — Vector of current values at two points [.0137, .545] A (default)

Dependencies

Voltages [V1 V2] — Vector of voltage values at two points [.6, .7] V (default)

Dependencies

Saturation current, IS — Saturation current 1e-12 A (default)

Dependencies

Emission coefficient, N — Diode emission coefficient 1 (default)

Dependencies

Current I1 — Current value 0.0137 A (default)

Dependencies

Voltage V1 — Voltage value 0.6 V (default)

Dependencies

Ohmic resistance, RS — Ohmic resistance 0 Ohm (default)

Dependencies

Measurement temperature — Measurement temperature 25 degC (default)

Forward currents, If(Tj,Vf) — Vector of forward currents [.07, .12, .19, 1.75, 4.24, 7.32, 11.2; .16, .3, .72, 2.14, 4.02, 6.35, 9.12] A (default) | nonnegative vector

Dependencies

Junction temperatures, Tj — Vector of junction temperatures [25, 125] degC (default)

Dependencies

Forward voltages, Vf — Vector of forward voltages [.5, .7, .9, 1.3, 1.7, 2.1, 2.5] V (default)

Dependencies

Number of series diodes — Number of diodes connected in series 1 (default)

Number of parallel diodes — Number of parallel diodes 1 (default)

Breakdown

Zener resistance — Zener resistance 0.3 Ohm (default)

Dependencies

Reverse breakdown voltage — Reverse breakdown voltage inf V (default)

Capacitance

Capacitance — Modeling junction capacitance Fixed or zero junction capacitance (default) | Use C-V curve data points | Use parameters CJ0, VJ, M & FC

Junction capacitance — Junction capacitance 5 pF (default)

Dependencies

Reverse bias voltages [VR1 VR2 VR3] — Vector of reverse bias voltage values [.1, 10, 100] V (default)

Dependencies

Corresponding capacitances [C1 C2 C3] — Vector of capacitance values [3.5, 1, .4] pF (default)

Dependencies

Zero-bias junction capacitance, CJ0 — Zero-bias junction capacitance 5 pF (default)

Dependencies

Junction potential, VJ — Junction potential 1 V (default)

Dependencies

Grading coefficient, M — Grading coefficient 0.5 (default)

Dependencies

Capacitance coefficient, FC — Capacitance coefficient 0.5 (default)

Dependencies

Charge dynamics — Charge dynamics parameterization Do not model charge dynamics (default) | Use peak reverse current and stretch factor | Use peak reverse current and reverse recovery time | Use peak reverse current and reverse recovery charge | Use transit time and carrier lifetime

Peak reverse current, iRM — Peak reverse current -7.15 A (default) | negative scalar

Dependencies

Initial forward current when measuring iRM — Initial forward current when measuring iRM 4 A (default) | positive scalar

Dependencies

Rate of change of current when measuring iRM — Rate of change of current when measuring iRM -750 A/μs (default) | negative scalar

Dependencies

Reverse recovery time stretch factor — Reverse recovery time stretch factor 3 (default)

`+` — Positive terminal
electrical

`-` — Negative terminal
electrical

`H` — Thermal port
thermal

`Diode model` — Diode model
`Piecewise Linear` (default) | `Exponential` | `Tabulated I-V curve`

`Forward voltage` — Forward voltage
`0.6` `V` (default)

`On resistance` — On resistance
`0.3` `Ohm` (default)

`Off conductance` — Off conductance
`1e-8` `1/Ohm` (default)

`Parameterization` — Model parameterization
`Use two I-V curve data points` (default) | `Use parameters IS and N` | `Use an I-V data point and IS` | `Use an I-V data point and N`

`Currents [I1 I2]` — Vector of current values at two points
`[.0137, .545]` `A` (default)

`Voltages [V1 V2]` — Vector of voltage values at two points
`[.6, .7]` `V` (default)

`Saturation current, IS` — Saturation current
`1e-12` `A` (default)

`Emission coefficient, N` — Diode emission coefficient
`1` (default)

`Current I1` — Current value
`0.0137` `A` (default)

`Voltage V1` — Voltage value
`0.6` `V` (default)

`Ohmic resistance, RS` — Ohmic resistance
`0` `Ohm` (default)

`Measurement temperature` — Measurement temperature
`25` `degC` (default)

`Forward currents, If(Tj,Vf)` — Vector of forward currents
`[.07, .12, .19, 1.75, 4.24, 7.32, 11.2; .16, .3, .72, 2.14, 4.02, 6.35, 9.12]` `A` (default) | nonnegative vector

`Junction temperatures, Tj` — Vector of junction temperatures
`[25, 125]` `degC` (default)

`Forward voltages, Vf` — Vector of forward voltages
`[.5, .7, .9, 1.3, 1.7, 2.1, 2.5]` `V` (default)

`Number of series diodes` — Number of diodes connected in series
`1` (default)

`Number of parallel diodes` — Number of parallel diodes
`1` (default)

`Zener resistance` — Zener resistance
`0.3` `Ohm` (default)

`Reverse breakdown voltage` — Reverse breakdown voltage
`inf` `V` (default)

`Capacitance` — Modeling junction capacitance
`Fixed or zero junction capacitance` (default) | `Use C-V curve data points` | `Use parameters CJ0, VJ, M & FC`

`Junction capacitance` — Junction capacitance
`5` `pF` (default)

`Reverse bias voltages [VR1 VR2 VR3]` — Vector of reverse bias voltage values
`[.1, 10, 100]` `V` (default)

`Corresponding capacitances [C1 C2 C3]` — Vector of capacitance values
`[3.5, 1, .4]` `pF` (default)

`Zero-bias junction capacitance, CJ0` — Zero-bias junction capacitance
`5` `pF` (default)

`Junction potential, VJ` — Junction potential
`1` `V` (default)

`Grading coefficient, M` — Grading coefficient
`0.5` (default)

`Capacitance coefficient, FC` — Capacitance coefficient
`0.5` (default)

`Charge dynamics` — Charge dynamics parameterization
`Do not model charge dynamics` (default) | `Use peak reverse current and stretch factor` | `Use peak reverse current and reverse recovery time` | `Use peak reverse current and reverse recovery charge` | `Use transit time and carrier lifetime`

`Peak reverse current, iRM` — Peak reverse current
`-7.15` `A` (default) | negative scalar

`Initial forward current when measuring iRM` — Initial forward current when measuring iRM
`4` `A` (default) | positive scalar

`Rate of change of current when measuring iRM` — Rate of change of current when measuring iRM
`-750` `A/μs` (default) | negative scalar

`Reverse recovery time stretch factor` — Reverse recovery time stretch factor
`3` (default)

`Reverse recovery time, trr` — Reverse recovery time
`115` (default)

`Reverse recovery charge, Qrr` — Reverse recovery charge
`1500` `s*μA` (default)

`Transit time, TT` — Transit time
`50` `ns` (default)

`Carrier lifetime, tau` — Carrier lifetime
`100` `ns` (default)

`Parameterization` — Temperature dependence parameterization
`None - Use characteristics at parameter measurement temperature` (default) | `Use an I-V data point at second measurement temperature` | `Specify saturation current at second measurement temperature` | `Specify the energy gap EG`

`Current I1 at second measurement temperature` — Current I1 at second measurement temperature
`0.0245` `A` (default)

`Voltage V1 at second measurement temperature` — Voltage V1 at second measurement temperature
`0.5` `V` (default)

`Saturation current, IS, at second measurement temperature` — Saturation current, IS, at second measurement temperature
`1.25e-7` `A` (default)

`Second measurement temperature` — Second measurement temperature
`125` `°C` (default)

`Energy gap, EG` — Energy gap
`1.11` `eV` (default)

`Saturation current temperature exponent parameterization` — Saturation current temperature exponent parameterization
`Use nominal value for pn-junction diode (XTI=3)` (default) | `Use nominal value for Schottky barrier diode (XTI=2)` | `Specify a custom value`

`Saturation current temperature exponent, XTI` — Saturation current temperature exponent
`3` (default)

`Reverse breakdown voltage temperature coefficient, dBV/dT` — Reverse breakdown voltage temperature coefficient
`0` `V/K` (default)

`Device simulation temperature` — Device simulation temperature
`25` `°C` (default)

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