Transcript Compact Device Modelling for System Simulation - MOS-AK

Compact IGBT Modelling for
System Simulation
Philip Mawby
Angus Bryant
Background
• Compact modelling of IGBTs and diodes
• Warwick and Cambridge Universities, UK
• Collaboration with University of South Carolina, USA
• Developed for MATLAB/Simulink, PSpice
• Integrated device optimisation & parameter extraction in
MATLAB
• Proven for a wide range of devices &
conditions
• Includes full temperature dependency
Compact Device Models
• Excess carrier density modelled
• Critical to on-state and switching behaviour
• Ambipolar diffusion equation (ADE) describes
carrier density distribution
• Fourier series used to solve ADE
• Boundary conditions set by depletion layers,
MOS channel, emitter recombination, etc.
• Implemented in Simulink
• Block-diagram form (including circuit)
• Chopper cell circuit (inductive switching)
Model Details
• Excess carrier density (stored
charge) is one-dimensional for 90%
of CSR.
• Fourier series solves 1D carrier
density p(x,t) in CSR:

p( x, t ) 
 k ( x  x1 ) 

pk (t ) cos
x

x
2
1


k 0

• Fourier terms pk(t) solved by
ordinary differential equations
• Boundary conditions: CSR edges
x1,x2 and gradients dp/dx (set by
currents).
• Depletion layer voltage Vd2
provides feedback to keep p(x2)=0.
• Classic MOS model used to
determine e- current In2.
General arrangement of CSR and depletion
layer during turn-off
Model Capabilities
• Temperature-enabled
• Proven capability from –150°C to +150°C.
• IGBT structures:
• 2-D effects (gate structure) accounted for
• Buffer layer enabled: choice of NPT/PT
(including FS/SPT devices)
• Local lifetime control enabled
IGBT Model Outline
Base region resistance
(conductivity modulation)
Emitter recombination (injection)
Carrier storage region (CSR) with
Fourier series solution
Depletion layer equations
Classic MOSFET model
Miller capacitance
Kelvin emitter inductance
Device Matching - 1
• Full chopper cell • All parasitics required (especially stray inductances).
• Initial fit by hand • Estimates of unknown parasitics and parameters.
Device Matching - 2
• IGBT and diode
parameter sets
for compact
models.
Device Matching - 3
• Inductive switching shown here. • Instantaneous power dissipations
• IGBT turn-on (left), IGBT turn-off
shown to validate switching
(right).
energies.
Device Matching - 4
• Inductive switching shown here. • Instantaneous power dissipations
• IGBT turn-on (left), IGBT turn-off
shown to validate switching
(right).
energies.
Device Matching - 5
On-state (forward voltage) shown here.
Turn-on Waveforms
Given at different temperatures and load currents
x-axis is time (us)
Turn-off Waveforms
Given at different temperatures and load currents
x-axis is time (us)
Power Converter Modelling
• IGBT model used in full converter modelling
• Simulation of every switching event is too time-consuming.
• Look-up table of losses is used instead:
•
•
•
•
Generated from device models in MATLAB/Simulink.
Gives losses as a function of load current and temperature.
Simple converter/heatsink model then simulates device temperature.
Rapid and accurate estimation of device temperature for whole load cycle.
EXTERNAL
CONDITIONS
Converter
simulation
Device temp.
System
modelling
Look-up
table
LOSS DATA
Simulation
controller
Power diss.
Heatsink
model
Device
modelling
Compact
models
Look-up Table of Losses
• IGBT power losses (W) for whole switching cycle plotted as a
function of load current (A), duty ratio and temperature (°C).
Full System Simulation
• Example is hypothetical
electric vehicle, running
standard Federal Urban
Driving Schedule.
• Simple drive model gives
inverter electrical
conditions.
• Resulting IGBT
temperature profile
plotted in relation to the
vehicle speed.
• Peaks in temperature
correspond to
acceleration/deceleration.
Conclusions
• Accurate modelling of device losses
• Temperature-enabled
• Proven over a wide range of conditions
• Model can be used to predict behaviour
• Already demonstrated with integrated optimisation.
• Integration with system simulation.
• Whole system runs in MATLAB and Simulink.
• Look-up table decouples device and system simulation.
• Future work will investigate device reliability
• Based on device temperature profiles and thermal
cycling data for device packaging.