Circuit Arrangement for Measuring Current

A circuit arrangement for measuring current in a conductor through which a current flows, the arrangement comprising:

• a current transformer configured to generate an input voltage from the current in the conductor;
• a diode bridge circuit, the current being supplied to an input of the diode bridge circuit, and a first output of the diode bridge circuit being located at a connection of two identical first electrodes of diodes of the diode bridge circuit;
• a measuring resistor for measuring current inserted between two identical second electrodes of the diodes of the diode bridge circuit, a the type of the second electrodes differs from a type of the first electrodes;
• a second output of the diode bridge circuit located at a connection of one diode of the diodes diode bridge circuit to the second electrodes and the measuring resistor;
• an extended bridge node is located at the connection of the other diodes to the second electrodes and the measuring resistor, a diode of the diode bridge circuit which is located at the second output being formed by a source-drain diode of a first normally-off field-effect transistor, and a diode of the diode bridge circuit, which is located at the extended bridge node being formed by a source-drain diode of a second normally-off field-effect transistor;
• a control apparatus configured to actuate a gate of the first field-effect transistor and a gate of the second field-effect transistor via a control voltage which is identical in each case to switch the circuit arrangement between a charging mode for a capacitor connecting the first output to the extended bridge node and a measuring mode;
• and
• a measuring apparatus configured, in the switched measuring mode, to measure a measuring voltage at the measuring resistor which is proportional to the current in the conductor.