Interference-free transmission of signals between different earth potentials

A voltage converter (100) for converting between a DC voltage at a DC voltage gate (101) and a multiphase AC voltage at an AC voltage gate (102), comprising an arrangement of switching elements (103a-103f), via which each phase (102a-102c) of the AC voltage gate (102) can be selectively connected to the positive pole or to the negative pole of the DC voltage gate (101), wherein a coupler (1) is provided for transmitting an analog control signal (3) between a first gate driver which is associated with the first switching element (103a-103f) of the arrangement and a second gate driver which is associated with a second switching element (103a-103f) which is associated with another phase (102a-102c) of the AC voltage gate (102), wherein the coupler (1) transmits the control signal (3) output by at least one transmitter (2) having a first ground potential (2a), via at least a first signal line (4a) and a second signal line (4b), to a receiver (5) having a second ground potential (5a), wherein the coupler (1) comprises:

• a filter arrangement (6) configured to receive a first component (3a) of the signal (3) transmitted via the first signal line (4a) and a second component (3b) of the signal (3) via the second signal line (4b) and filter each of the first component (3a) and the second component (3b) separately, wherein this filter arrangement (6) is potential-free or uses the second ground potential (5a);
• a polarity reversal protection element (9);
• and
• a comparator (7),
• wherein the first component (3a′) and the second component (3b′), after being filtered by the filter arrangement (6), are combined in the comparator (7) to form a signal (8) to be supplied to the receiver (5), and wherein the comparator (7) uses the second ground potential (5a), and wherein the comparator (7) subtracts the first component (3a′) and the second component (3b′) transmitted via both signal lines from one another,
• wherein the polarity reversal protection element (9) is designed to divert a voltage that is present on at least one signal line (4a, 4b) and is outside of the specification of at least one input (7a, 7b) of the comparator (7) away from this input (7a, 7b), and
• wherein the polarity reversal protection element (9) comprises a series circuit of two diodes (9c, 9d) that is connected in the reverse direction between two predetermined potentials (9a, 9b), and wherein the input (7a, 7b) of the comparator (7) is connected to the connection between the two diodes (9c, 9d) in the series circuit.