Ramp Load

The Ramp Load subcircuit models a single, non-repeating ramp or step in load current using a resistor and a PWL current source.

  • The resistor models the starting, or minimum, load current.
  • The PWL current source models the ramp portion of the load current.

In DVM, the Ramp Load subcircuit is used in the StepLoad() test objective. You can change any managed DVM load to use the Ramp Load by entering a Ramp() entry in the Load column.

Other similar loads include the following:

In this topic:

  DVM Information Power Supply (Non-DVM) Information
Model Name Ramp Load
Simulator
Parts Selector
Menu Location
  • DVM > Loads > DVM Output Load - 2 Terminal
  • DVM > Loads > DVM Output Load - 3 Terminal
  • DVM > Loads > DVM Output Load - 4 Terminal
Power Supply Loads > Power Supply Load ( DC Current, Pulse, Bode, Zout... )
Symbol Library SIMPLIS_DVM_ADVANCED.sxslb power_supply_source_and_loads.sxslb
Model File SIMPLIS_DVM_ADVANCED.lb power_supply_source_and_loads.lb
Subcircuit Name
  • SIMPLIS_DVM_ADVANCED_LOAD_2T_RAMP
  • SIMPLIS_DVM_ADVANCED_LOAD_3T_RAMP
  • SIMPLIS_DVM_ADVANCED_LOAD_4T_RAMP
 POWER_SUPPLY_LOAD_RAMP
Symbols
Schematic - 2 Terminal
Note: Power Supply probes will not have the "DVM" prefix.
Schematic - 3 Terminal
Note: Power Supply probes will not have the "DVM" prefix.
Schematic - 4 Terminal
Note: Power Supply probes will not have the "DVM" prefix.

Parameters

The table below explains the parameters used in the Ramp Load subcircuit.

Parameter Name Default Data Type Range Units Parameter Description
FINAL_CURRENT 750m Real min: 0 A The final current for the PWL current source portion of the load. The Ramp Load continues at this current for all simulation times greater than TIME_DELAY + RISE_TIME. This can be a numeric value or a symbolic value, such as a percentage of full load.
LOAD_NAME LOAD String n/a n/a Name of the DVM load. This name cannot contain spaces.
LOAD_RESISTANCE 2.00667 Real min: 0 Ω The resistance value which models the starting current of the load
RISE_TIME 100u Real min: 0 s The ramp rise time in seconds
START_CURRENT 0 Real min: 0 A The starting current for the PWL current source portion of the load. This is typically set to 0 since the minimum load current is modeled with the LOAD_RESISTANCE parameter. This can be a numeric value or a symbolic value, such as a percentage of full load.
TIME_DELAY 10u Real min: 0 s The time delay before the ramp initiates

DVM Testplan Entry

To set any managed DVM load to a Ramp Load subcircuit, place a Ramp() testplan entry in the Load column.

The Ramp() testplan entry has the following syntax with the arguments explained in the table below.

Ramp(REF, ISTART, IFINAL)
Ramp(REF, ISTART, IFINAL, OPTIONAL_PARAMETER_STRING)
Argument Range Description
REF n/a The actual reference designator of the DVM load or the more generic syntax of OUTPUT:n where n is an integer indicating a position in the list of managed DVM loads. 
ISTART min: 0 The starting current for the load. This can be a numeric value or a symbolic value, such as percentage of full load.
IFINAL min: 0 The final current for the load. This can be a numeric value or a symbolic value, such as a percentage of full load.
OPTIONAL_PARAMETER_STRING n/a Parameter string with timing parameters TIME_DELAY and/or RISE_TIME*

*    If both parameters are specified, join the two parameter key-value pairs with a space, as shown in the example below. The order of the parameter names does not matter.

DVM calculates the LOAD_RESISTANCE parameter from the ???MATH???I_{START}???MATH??? argument and subtracts the equivalent starting current from the PWL portion of the load. The calculation for the LOAD_RESISTANCE parameter is based on the following:

  • The nominal output voltage which is entered in the Output page of the Full Power Assist DVM control symbol.
  • The starting load current given in the Ramp() function or the StepLoad() objective.
Note: If the specified starting current is 0 and the load is configured by DVM using either a Ramp() function or the StepLoad() test objective, DVM replaces the Ramp Load subcircuit with a Ramp Pure Load subcircuit. The Ramp Pure Load does not use a parallel resistance to model the starting current.

Timing

During a StepLoad() test, DVM sets the output under test to use the Ramp Load subcircuit. Then DVM sets the TIME_DELAY and RISE_TIME parameters for the Ramp Load. You can change the timing with the Ramp() function call by providing the timing parameters as an optional parameter string, which is the fourth argument to the Ramp() function call.

DVM Example

The following example sets the first DVM managed load to a Ramp Load with a starting current of 1A and a final current of 5A.

Note: In this example, the Load column is the first column in the testplan and, therefore, begins with the special three character sequence: *?@.
*?@ Load
Ramp(OUTPUT:1, 1, 5, TIME_DELAY=25u RISE_TIME=100u)

The results of this testplan entry are shown below:

Annotation Value
X0 TIME_DELAY
X1 TIME_DELAY + RISE_TIME
Y0 ISTART(see note below)
Y1 IFINAL (see note below)
Note: The actual load current depends on the LOAD_RESISTANCE parameter and the actual time-varying load voltage. The ISTART current is modeled by a resistor with a resistance equal to the value of LOAD_RESISTANCE . The PWL current source has points defined by the START_CURRENT and FINAL_CURRENT parameter values.

Converting between DVM and Power Supply Loads

To change a Power Supply load to a DVM load, right click the symbol to bring up the context menu, and select the menu option: Upgrade to DVM Source/Load

To change a DVM load to a Power Supply load, right click the symbol to bring up the context menu, and select the menu option: Downgrade to SIMetrix/SIMPLIS Source/Load

Collected links
StepLoad() Test Objective
Load
Ramp Pure Load
Pulse Load - Single Current Pulse
Pulse Load - Single Pure Current Pulse
Symbolic Values
Managed Sources and Loads
Full Power Assist DVM Control Symbol
Ramp Load