CIRCU125


Diode

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CIRCU125 Element Description

CIRCU125 is a diode element normally used in electric circuit analysis. The element may also interface with electromagnetic and mechanical finite elements to simulate fully coupled electromechanical analyses at the lumped parameter level. The element has 2 nodes to define the circuit component and one degree of freedom per node to model the circuit response. The element may interface with the electric circuit element CIRCU124, with the mechanical elements MASS21, COMBIN14, and COMBIN39, and with the electromechanical transducer element TRANS126. CIRCU125 is applicable to static analyses and transient analyses with restart.

CIRCU125 Input Data

The geometry, node definition, and degree of freedom options are shown in Figure 125.1: CIRCU125 Element Options.

The diode element is defined by the KEYOPT(1) setting and its corresponding real constants. Real constant input is dependent on the diode option used. A summary of the element input options is given in "CIRCU125 Input Summary". Real constants numbers 1 and 2 are created by the GUI Circuit Builder (see the Modeling and Meshing Guide), and are not required input for analysis purposes. The element is characterized by one degree of freedom, VOLT (voltage).

Figure 125.1: CIRCU125 Element Options

CIRCU125 Element Options

The I-U characteristics of the diodes are approximated by the piecewise linear functions shown in Figure 125.2: CIRCU125 I-U Characteristics. The characteristic of a common (non-Zener) diode consists of line segments corresponding to the closed and open states. The characteristic of a Zener diode consists of three segments corresponding to the Zener, closed, and open states. The diode characteristic can be ideal or lossy depending on the values of the real constants.

Figure 125.2: CIRCU125 I-U Characteristics

CIRCU125 I-U Characteristics

CIRCU125 Input Summary

Nodes

I, J

Degrees of Freedom

VOLT

Real Constants
Dependent on KEYOPT(1) settings.
For KEYOPT(1) = 0:
GOFFST, ID, (blank), RESF, VLTF, RESB,
(blank), (blank)
For KEYOPT(1) = 1:
GOFFST, ID, (blank), RESF, VLTF, RESB,
RESZ, VLTZ
See Table 125.1: CIRCU125 Real Constants.
Material Properties

None

Surface Loads

None

Body Loads

None

Special Features

None

KEYOPT(1)

Select diode options:

0 -- 

Common Diode

1 -- 

Zener Diode

KEYOPT(7)

Element level time increment control:

0 -- 

No control

1 -- 

Predictions are made to achieve a reasonable time (or load) increment

If you are using the Circuit Builder to construct your model, the real constants GOFFST and ID are provided automatically.


Note:  The real constant default values may not be appropriate to analyze micro devices (that is, devices with extremely small dimensions) in MKSA units.


Table 125.1: CIRCU125 Real Constants

Real Constant No.NameDescription
Common Diode (D) (KEYOPT(1) = 0)
1GOFFSTGraphical offset
2IDElement identification number
3--(blank)
4RESFForward resistance (if not entered, defaults to 1.0e-12 Ohm)
5VLTFForward voltage (if not entered, defaults to 0.0e0 Volt)
6RESBBlocking resistance (if not entered, defaults to 1.0e+12 Ohm)
7, 8--(blank)
Zener Diode (Z) (KEYOPT(1) = 2) - use real constants 1 through 6 as above, then:
7RESZZener resistance (if not entered, defaults to 1.0e+12 Ohm)
8VLTZZener voltage (if not entered, defaults to 1.0e-12 Volt)

CIRCU125 Solution Considerations

CIRCU125 is a highly nonlinear element. To obtain convergence, you may have to define convergence criteria instead of using the default values. Use CNVTOL,VOLT,,0.001,2,1.0E-6 if you need to change the convergence criteria.

CIRCU125 Output Data

The element output for this element is dependent on the circuit option selected. Table 125.2: CIRCU125 Element Output Definitions summarizes the element output data.

The Element Output Definitions table uses the following notation:

A colon (:) in the Name column indicates that the item can be accessed by the Component Name method (ETABLE, ESOL). The O column indicates the availability of the items in the file jobname.out. The R column indicates the availability of the items in the results file.

In either the O or R columns, “Y” indicates that the item is always available, a letter or number refers to a table footnote that describes when the item is conditionally available, and “-” indicates that the item is not available.

Table 125.2: CIRCU125 Element Output Definitions

NameDefinitionOR
For KEYOPT(1) = 0: Common Diode
ELElement NumberYY
NODESNodes - I, JYY
RESTTangent ResistanceYY
VOLTAGEVoltage drop between node I and node JYY
CURRENTCurrentYY
POWER Power lossYY
STATDiode status11
DYNRESDynamic resistance at operating pointYY
AMPGENNorton equivalent current generatorYY
For KEYOPT(1) = 1: Zener Diode
ELElement NumberYY
NODESNodes - I, JYY
RESTTangent resistanceYY
VOLTAGEVoltage drop between node I and node JYY
CURRENTCurrentYY
POWER Power lossYY
STATDiode status22
DYNRESDynamic resistance at operating pointYY
AMPGENNorton equivalent current generatorYY

  1. Common Diode Status Values

    1 - Forward, open

    2 - Reverse, blocked

  2. Zener Diode Status Values

    1 - Forward, open

    2 - Reverse, blocked

    3 - Zener, breakdown

Table 125.3: CIRCU125 Item and Sequence Numbers lists output available through the ETABLE command using the Sequence Number method. See The General Postprocessor (POST1) in the Basic Analysis Guide and The Item and Sequence Number Table in this reference for more information. The following notation is used in Table 125.3: CIRCU125 Item and Sequence Numbers:

Name

output quantity as defined in Table 125.2: CIRCU125 Element Output Definitions

Item

predetermined Item label for ETABLE command

E

sequence number for single-valued or constant element data

Table 125.3: CIRCU125 Item and Sequence Numbers

Output Quantity NameETABLE and ESOL Command Input
ItemE
VOLTAGESMISC1
CURRENTSMISC2
POWERNMISC1
blankNMISC2
blankNMISC3
DYNRESNMISC4
AMPGENNMISC5
STATNMISC6

CIRCU125 Assumptions and Restrictions

  • If either the Zener voltage or Zener resistance is blank or very small, the Zener diode will be replaced with a common diode and a warning will be issued.

  • Only MKS units are allowed (EMUNIT command).

  • If the Zener Voltage is entered as a positive number, the element will negate the entered value. If the Forward Voltage is entered as a negative number, the element will replace it with its absolute value. All resistance must be positive. Any negative resistance value is replaced by its absolute value.

  • This element does not support harmonic analysis.

  • This element does not work with the CIRCU94 piezoelectric element.

  • This element may not be compatible with other elements with the VOLT degree of freedom. To be compatible, the elements must have the same reaction force (see Element Compatibility in the Low-Frequency Electromagnetic Analysis Guide).

  • This element cannot be used in a distributed-memory parallel solution.

CIRCU125 Product Restrictions

There are no product-specific restrictions for this element.