Protection circuit connecting and disconnecting a DC operated device from a DC power source

A protection circuit for connecting and disconnecting a DC operated application device from a DC power source, comprising

• a first input terminal and a second input terminal for receiving power from the DC power source;
• a first output terminal and a second output terminal for providing power to the DC operated application device;
• a first stage comprising a voltage measurement circuit coupled between the first and second input terminals;
• a second stage following the first stage comprising a pre-charge control circuit and a pre-charge capacitor in series with the pre-charge control circuit, the second stage is in parallel with the first stage between the first and second input terminals, wherein the pre-charge control circuit includes a power source in parallel with a bypass switch;
• a digital controller arranged for controlling activating and de-activating of a local power supply unit (PSU) for supplying power to electronics of the DC operated application device;
• wherein the digital controller is arranged for:
• measuring an input voltage level of the voltage measurement circuit indicative of the voltage level of the first input terminal;
• determining a pre-charge condition by measuring a voltage level across the pre-charge capacitor and comparing the voltage level across the pre-charge capacitor with the input voltage level;
• operating the bypass switch based on the determined pre-charge condition such that when the voltage across the capacitor matches the input voltage the digital controller is arranged to close the bypass switch and activate the local PSU;
• de-activating the local PSU when detecting a voltage drop having a voltage dropping slope of the first input terminal that exceeds a predetermined threshold in voltage level drop and/or a threshold of the voltage dropping slope.