SimElectronics™

N-Channel IGBT - Model N-Channel IGBT

Library

Semiconductor Devices

Description

The N-Channel IGBT block models a PNP Bipolar transistor driven by an N-Channel MOSFET, as shown in the following figure:

The MOSFET source is connected to the bipolar transistor collector, and the MOSFET drain is connected to the bipolar transistor base. The MOSFET uses the equations shown in the N-Channel MOSFET block reference page. The bipolar transistor uses the equations shown in the PNP Bipolar Transistor block reference page, but with the addition of an emission coefficient parameter N that scales kT/q.

The N-Channel IGBT block uses the on and off characteristics you specify in the block dialog box to estimate the parameter values for the underlying N-Channel MOSFET and PNP bipolar transistor.

• The block uses the off characteristics to calculate the base-emitter voltage, V_be, and the saturation current, I_S

  1. When the transistor is off, the gate-emitter voltage is zero and the IGBT base-collector voltage is large, so the PNP base and collector current equations simplify to:

     

     where N is the Emission coefficient N parameter value, I_c is the Zero gate voltage collector current Ices parameter value, and I_c and I_b are defined as positive flowing out of the collector and base respectively. See the PNP Bipolar Transistor reference page for definitions of the remaining variables.

  2. The block sets β_R and β_F to typical values of 1 and 50, so these two equations can be used to solve for V_be and I_S:

     

     Note   The block doesn't require and exact value for βF because it can adjust the MOSFET gain K to ensure the overall device gain is correct.

• The block uses the on characteristics to calculate the MOSFET gain, K.

  1. The block approximates the base saturation current as

     where I_ce(sat) is the Collector-emitter saturation current Ice(sat) parameter value.

  2. When saturated, PNP transistor base current equation simplifies to:

     

     The block substitutes I_b(sat) for I_b and solves this equation for V_be(sat):

     

  3. When saturated, the MOSFET equation is:

     

     where V_th is the Gate-emitter threshold voltage Vge(th) parameter value and V_GE(sat) is the Gate-emitter voltage for {Vce(sat),Ice(sat)} parameter value.

     V_ds is related to the transistor voltages as V_ds = V_CE – V_be. The block substitutes this relationship for V_ds, sets the base-emitter voltage and base current to their saturated values, and rearranges the MOSFET equation to give

     

     where V_CE(sat) is the Collector-emitter saturation voltage Vce(sat) parameter value.

  These calculations ensure the zero gate voltage collector current and collector-emitter saturation voltage are exactly met at these two specified conditions. However, the current-voltage plots are very sensitive to the emission coefficient N and the precise value of V_th. If the manufacturer datasheet gives current-voltage plots for different V_GE values, then the N and V_th can be tuned by hand to improve the match.

The block models gate junction capacitance as a fixed gate-emitter capacitance C_GE and a fixed gate-collector capacitance C_GC. If you select Specify using equation parameters directly for the Parameterization parameter, you specify these values directly using the Gate-emitter junction capacitance and Gate-collector junction capacitance parameters. Otherwise, the block derives them from the Input capacitance Cies and Reverse transfer capacitance Cres parameter values that IGBT datasheets usually provide. The two parameterizations are related as follows:

• C_GE = Cres

• C_GC = Cies – Cres

Basic Assumptions and Limitations

The model is based on the following assumptions:

• This block does not allow you to specify initial conditions on the junction capacitances. If you select the Start simulation from steady state option in the Solver Configuration block, the block solves the initial voltages to be consistent with the calculated steady state. Otherwise, voltages are zero at the start of the simulation.

• This block does not model temperature-dependent effects. SimElectronics simulates the block at the temperature at which the component behavior was measured, as specified by the Measurement temperature parameter value.

• You may need to use nonzero junction capacitance values to prevent numerical simulation issues, but the simulation may run faster with these values set to zero.

Dialog Box and Parameters

Main Tab

Zero gate voltage collector current Ices

The collector current that flows when the gate-emitter voltage is set to zero, and a large collector-emitter voltage is applied i.e. the device is in the off-state. The default value is 2 mA.

Gate-emitter threshold voltage Vge(th)

The threshold voltage used in the MOSFET equations. The default value is 6 V.

Collector-emitter saturation voltage Vce(sat)

The collector-emitter voltage for a typical on-state as specified by the manufacturer. The default value is 2.8 V.

Collector-emitter saturation current Ice(sat)

The collector-emitter current when the gate-emitter voltage is V_ge(sat) and collector-emitter voltage is V_ce(sat). The default value is 400 A.

Gate-emitter voltage for {Vce(sat),Ice(sat)}

The gate voltage used when measuring V_ce(sat) and I_ce(sat). The default value is 15 V.

Emission coefficient N

The emission coefficient or ideality factor of the bipolar transistor. The default value is 1.

Measurement temperature

The temperature for which the parameters are quoted. It is also the temperature at which the device is simulated. The default value is 25 C.

Junction Capacitance Tab

Parameterization

Select one of the following methods for block parameterization:

• Specify from a datasheet — Provide parameters that the block converts to junction capacitance values. This is the default method.

• Specify using equation parameters directly — Provide junction capacitance parameters directly.

Input capacitance Cies

The gate-emitter capacitance with the collector shorted to the source. This parameter is only visible when you select Specify from a datasheet for the Model junction capacitance parameter. The default value is 26.4 nF.

Reverse transfer capacitance Cres

The collector-gate capacitance with the emitter connected to ground. This parameter is only visible when you select Specify from a datasheet for the Model junction capacitance parameter. The default value is 2.7 nF.

Gate-emitter junction capacitance

The value of the capacitance placed between the gate and the emitter. This parameter is only visible when you select Specify using equation parameters directly for the Model junction capacitance parameter. The default value is 23.7 nF.

Gate-collector junction capacitance

The value of the capacitance placed between the gate and the collector. This parameter is only visible when you select Specify using equation parameters directly for the Model junction capacitance parameter. The default value is 2.7 nF.

Ports

The block has the following ports:

C

Electrical conserving port associated with the PNP emitter terminal.

G

Electrical conserving port associated with the MOSFET gate terminal.

E

Electrical conserving port associated with the PNP collector terminal.

Light-Emitting Diode

N-Channel JFET