MOSFET with Diode
Purpose
Ideal MOSFET with ideal anti-parallel diode
Library
Electrical / Power Semiconductors
Description
This model of a Metal Oxide Semiconductor Field Effect Transistor has an integrated anti-parallel diode. The diode is usually included in power MOSFET packages.
This device is modeled as a single ideal switch that closes when the gate signal is not zero or the voltage becomes negative and opens when the gate signal is zero and the current becomes positive.
Note
Due to the switching conditions described above, this device cannot be turned off actively while the current is exactly zero. This may result in unexpected voltage waveforms if the device is used e.g. in an unloaded converter.
To resolve this problem, either use an individual MOSFET with an individual anti-parallel Diode, or allow a small non-zero load current to flow by connecting a large load resistance to the converter.
Parameters
- Initial conductivity
Initial conduction state of the device. The device is initially blocking if the parameter evaluates to zero, otherwise it is conducting. This parameter may either be a scalar or a vector corresponding to the implicit width of the component. The default value is
0.- Thermal description
Switching losses, conduction losses and thermal equivalent circuit of the component. For more information see chapters Thermal Modeling and Losses of Semiconductor Switch with Diode.
- Thermal interface resistance
The thermal resistance of the interface material between case and heat sink, in \((\mathrm{K}/\mathrm{W})\). The default is
0.- Number of parallel devices
This parameter is used to simulate the effect of connecting multiple identical devices in parallel while adding only one single switch element to the electrical system equations. Other component parameters such as the Thermal description and the Thermal interface resistance refer to the characteristics of an individual device, while the calculated losses and other probe signals refer to the sum over all devices.
If \(N_\mathrm{p}\) is the number of parallel devices, each device will conduct \(1/N_\mathrm{p}\) of the total current through the component, and the total component loss will be \(N_\mathrm{p}\) times the loss of an individual device. The effective thermal interface resistance of the component is also \(1/N_\mathrm{p}\) times the respective parameter value. The default is
1.Example Model
See the example model “Thermal Modelling with Parallel Devices”.
Find it in PLECS under Help > PLECS Documentation > List of Example Models.
- Initial temperature
This parameter is used only if the device has an internal thermal impedance and specifies the temperature of the thermal capacitance at the junction at simulation start. The temperatures of the other thermal capacitances are initialized based on a thermal “DC” analysis. If the parameter is left blank, all temperatures are initialized from the external temperature. See also Temperature Initialization.
Probe Signals
- Device voltage
The voltage measured between drain and source. The device voltage can never be negative.
- Device current
The current through the device. The current is positive if it flows through the MOSFET from drain to source and negative if it flows through the diode from source to drain.
- Device gate signal
The gate input signal of the device.
- Device conductivity
Conduction state of the internal switch. The signal outputs \(0\) when the device is blocking, and \(1\) when it is conducting.
- Device junction temperature
Temperature of the first thermal capacitor in the equivalent Cauer network.
- Device conduction loss
Continuous thermal conduction losses in watts \((\mathrm{W})\). Only defined if the component is placed on a heat sink.
- Device switching loss
Instantaneous thermal switching losses in joules \((\mathrm{J})\). Only defined if the component is placed on a heat sink.