Thyristor, TRIAC and DIAC.

The Silicon Controlled Rectifier (SCR), TRIAC and DIAC are models that are based on the diode model. The main difference for the SCR and TRIAC 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 SCR and TRIAC from the semiconductor library are 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. The ideal circuit component DIAC can be combined with the SCR and TRIAC model from the semiconductor library.

Since the ideal circuit components are described in the reference guide, only the models from the semiconductor library are discussed here.

Static characteristics
The static characteristics include the turn on and turn off parameters. Te minimum latch and hold current are specified here as well as the on state characteristics.

Dynamics
The SCR and TRIAC are turned on, when the voltage over the component rises to fast. The maximum du/dt can be specified.

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

SCR Static Parameters
ParameterDefaultFunction
BV1e6Breakdown voltage, if the voltage accross the device is larger than BV, the device turns on.
IHold1The minimum current during on-state to keep the device in conductive on-state
ILatch1The minimum current when changing from off to on-state.
Igt300mThe minimum gate current when changing from off to on-state.
Vgt3The minimum gate voltage (with reference to terminal T1 for the TRIAC) when changing from off to on-state.
Ron10mOn-state resistance.
Roff100kOff-state resistance.
Von1On-state series voltage.

SCR Dynamic Parameter
ParameterDefaultFunction
dU/dt[V/us]1000Maximum transient voltage rise. If the voltage rises faster than this value, the SCR is turned on.

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

TRIAC Static Parameters
ParameterDefaultFunction
BV1e6Breakdown voltage, if the voltage accross the device is larger than BV, the device turns on.
IHold1The minimum current during on-state to keep the device in conductive on-state
ILatch1The minimum current when changing from off to on-state.
Igt300mThe minimum gate current when changing from off to on-state.
Vgt3The minimum gate voltage (with reference to terminal T1 for the TRIAC) when changing from off to on-state.
Ron10mOn-state resistance.
Roff100kOff-state resistance.
Von1On-state series voltage.

TRIAC Dynamic Parameter
ParameterDefaultFunction
dU/dt[V/us]1000Maximum transient voltage rise. If the voltage rises faster than this value, the TRIAC is turned on.

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