Diode
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).
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.
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 (i.e., devices with extremely small dimensions) in MKSA units.
Table 125.1: CIRCU125 Real Constants
| Real Constant No. | Name | Description |
|---|---|---|
| Common Diode (D) (KEYOPT(1) = 0) | ||
| 1 | GOFFST | Graphical offset |
| 2 | ID | Element identification number |
| 3 | -- | (blank) |
| 4 | RESF | Forward resistance (if not entered, defaults to 1.0e-12 Ohm) |
| 5 | VLTF | Forward voltage (if not entered, defaults to 0.0e0 Volt) |
| 6 | RESB | Blocking 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: | ||
| 7 | RESZ | Zener resistance (if not entered, defaults to 1.0e+12 Ohm) |
| 8 | VLTZ | Zener 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 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
| Name | Definition | O | R |
|---|---|---|---|
| For KEYOPT(1) = 0: Common Diode | |||
| EL | Element Number | Y | Y |
| NODES | Nodes - I, J | Y | Y |
| REST | Tangent Resistance | Y | Y |
| VOLTAGE | Voltage drop between node I and node J | Y | Y |
| CURRENT | Current | Y | Y |
| POWER | Power loss | Y | Y |
| STAT | Diode status | 1 | 1 |
| DYNRES | Dynamic resistance at operating point | Y | Y |
| AMPGEN | Norton equivalent current generator | Y | Y |
| For KEYOPT(1) = 1: Zener Diode | |||
| EL | Element Number | Y | Y |
| NODES | Nodes - I, J | Y | Y |
| REST | Tangent resistance | Y | Y |
| VOLTAGE | Voltage drop between node I and node J | Y | Y |
| CURRENT | Current | Y | Y |
| POWER | Power loss | Y | Y |
| STAT | Diode status | 2 | 2 |
| DYNRES | Dynamic resistance at operating point | Y | Y |
| AMPGEN | Norton equivalent current generator | Y | Y |
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
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 solution.