A description is given of an apparatus for disconnecting a connection between solar modules of a photovoltaic string. A circuit breaker, a band-stop filter and a supply circuit are arranged in a series circuit between a first and second terminal. The series circuit is configured to conduct a current that includes a DC string current flowing through the photovoltaic string and a high-frequency control signal modulated onto the DC string current. The supply circuit is configured to generate energy to power the apparatus from the DC string current. An AC bypass circuit bridges the circuit breaker in parallel and is configured to conduct the high-frequency control signal. A control unit is configured to operate the apparatus based on the high-frequency control signal. A reverse current diode oppositely polarized relative to an operating current flow is connected in parallel with the circuit breaker or the circuit breaker and the band-stop filter.