Circuit arrangement for reducing power loss in the case of an active electrical current output of a field device

A circuit arrangement for reducing power loss in the case of an active electrical current output of a field device for determining and/or influencing a process variable, said electrical current output being connected with an external load and said process variable being represented via a selectable electrical current value, said circuit arrangement comprising:

• an external voltage supply;
• a voltage regulator for converting a voltage delivered by an external voltage supply into a lower voltage;
• and
• a control loop associated with said voltage regulator,
• said external load being coupled with the voltage regulator,
• said control loop including:
• an electrical current controller for setting the electrical current value, an analog-digital converter, a computation/control unit and a reference resistor, which is connected in series with said electrical current controller and to a reference potential, said computation/control unit being coupled with said voltage regulator and with said analog-digital converter, and said analog-digital converter being adapted to measure a voltage applied to the reference resistor, to digitize the measured voltage and to forward the digital voltage value to said computation/control unit;
• wherein:
• the computation/control unit is adapted to calculate a voltage to be delivered by the voltage regulator based on:
• said measured voltage forwarded by the analog-digital converter, a known resistance value of the reference resistor and the electrical current value currently to be set, and to operate the electrical current controller for setting the electrical current value and to operate the voltage regulator for tuning the voltage delivered by the voltage regulator as a function of the presently set electrical current value,
• and the control loop is so embodied that the voltage regulator, as a function of the presently set electrical current value, controls the voltage delivered.