MOS Controlled Thyristor, MCT.

The MOS Controlled Thyristor (MCT)is a models that is based on the diode model. The main difference for the MCT model from the semiconductor library compared to the circuit components is the circuit connection for the gate. The ideal circuit components have a block diagram gate control node, while the models from the semiconductor library have a circuit control node.
This means that the ideal circuit components are controlled by a block diagram signal, that is either 0 or 1. The MCT from the semiconductor library is controlled from a circuit.

What model is required
When one is only interested in the overall system analysis, the ideal circuit components are sufficient. When the entire control circuit has to be modeled, the models from the semiconductor library are required.

Static characteristics
The static characteristics include the turn on and turn off parameters. The on state characteristics are defined by a forward voltage drop over the conducting MCT and a series resistance.

Dynamics
The Gate is modeled asa MOS input. This means charge has to build up in the MCT during turn-on and the charge has to be removed during turn-off. The Gate-Anode capacitance and the internal gate resistance can be defined. When the voltage over the Gate-Anode is crossing the threshold value, the device is switching. (Note, not the external Gate voltage!)

Overview of the MCT parameters
The parameters for the MCT are summarized in the following table. Default values for the parameters are given.

MCT Static Parameters
ParameterDefaultFunction
Ron10mOn-state resistance.
Roff100kOff-state resistance.
Von1On-state series voltage.

MCT Dynamic Gate Parameters
ParameterDefaultFunction
CGA1nFGate capacitance.
RG10Internal Gate resistance.
VonGateThreshold-5To turn-on, the Gate-Anode voltage has to be less than -5 Volts.
VoffGateThreshold5To turn-off, the Gate-Anode voltage has to be larger than 5 Volts.

MCT Reverse Break Down Parameters
ParameterDefaultFunction
ReverseBreakDownVoltage25Breakdown voltage, if the voltage accross the device is larger than BV, the device turns on.
ReverseBreakDownCurrent1Breakdown current, if the voltage accross the device is larger than BV, the device turns on and the current is this specified value.
RonBreakDown1Resistance during break down.

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