Electric circuit arrangement and a method for a galvanically insulated, AC/DC sensitive differential-current measurement having high resolution

A measuring method for a galvanically insulated, AC/DC sensitive differential-current measurement, the measuring method comprising the following steps:

• detecting a differential current (Id) by means of a toroid current transformer (4) having at least one secondary winding (6),
• powering the secondary winding (6) by means of a driver circuit (12) which is configured as a structurally individual, integrated circuit,
• controlling the driver circuit (12) and generating a time-modulated binary oscillator signal (V) having dwell times (Th, T1) in a state 1 (S1) and in a state 2 (S2) by means of a first oscillator circuit (22),
• determining the corresponding dwell time (Th, T1) in the states 1 and 2 (S1, S2) by means of a second oscillator circuit (32), which is realized as a structurally individual, integrated circuit, by generating a clock signal (C) having a clock rate which is independent of the oscillator signal (V) and causes a high temporal resolution of smaller than 1 ns,
• evaluating the dwell times (Th, T1) by means of an evaluation device (42),
• outputting a differential-current measuring value (Im, I′m) by means of a data interface.