The ISOVLCL-3 is an isolated current and voltage regulator board intended specifically for use with Enerpro SCR firing boards. In a typical configuration, the regulator board accepts current and voltage feedback and command signals. The regulator circuit drives the firing board's delay angle command signal to produce the output current or voltage specified by the command signals.

Feedback signals for the regulator board are typically derived from a 0-50 mV current shunt and a 0-4 V DC full scale voltage signal (as supplied through an external attenuator).


  • Isolates Voltage and Current Feedback Signals
  • Automatic Crossover Between Regulation Modes
  • Current Trip with Automatic Reset
  • Soft-Start
  • Scaled Current and Voltage Read-Back Signals



The ISOVLCL3 includes the following features:

  • Isolated Voltage and Current Feedback Signals: The current and voltage feedback signals are galvanically isolated from the regulator board by Analog Devices AD202KN isolation amplifiers (1500 Vrms, 2000 V peak). 
  • Load Voltage or Current Limit: Limit amplifiers respond to the difference between either feedback signal and the corresponding limit commands. The resulting signal is the SCR delay angle command signal, SIG HI.
  • Current and Voltage Limit Automatic Crossover: A diode OR circuit provides automatic crossover between voltage and current limiting. The ISOVLCL-3 operates in either current or voltage regulating mode depending on which limit command setting is lowest.
  • Overcurrent Trip with Automatic Reset: A board-mounted potentiometer sets the current trip level. The current trip resets the soft-start circuit; its response time to an overcurrent event is approximately 3 milliseconds. If the over-current condition persists, the current trip will automatically reset and trip, cycling continuously until cleared.
  • Soft-Start and Soft-Stop: The soft-start circuit ramps the gate delay command voltage input to the firing board up to the preset level in approximately 2 seconds; the soft-stop ramps the command down in a similar fashion. Other soft-start times may be specified.
  • Polarity Reversing Compatability: The current and voltage feedback signals are processed by precision absolute value circuits, avoiding positive feedback and permitting operation with polarity reversing applications.
  • Voltage and Current Read-Back Signals: Scaled analog voltage and current signals are available from a dedicated connector.
  • Onboard or Offboard Voltage and Current Commands: Users may command the desired voltage or current level using board-mounted potentiometers or through externally applied voltage and current commands. Several command voltage or current ranges are available, including 0-12 V, 0-10 V, and 4-20 mA.
  • Board Construction: All circuit boards are assembled at the Enerpro plant in Goleta, California and are manufactured by a UL-approved fabricator from 2.4 mm thick FR4 fire resistant fiberglass epoxy laminate. All boards are conformal coated (MIL-1-46058, Type UR).


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