Protection circuit with a cut-off switch for power systems

A method of operating a power system comprising a power converter and a protection circuit between the power converter and a voltage supply, the method comprising:

• setting, by a first controller of the protection circuit, a cut-off switch of the protection circuit in an ON state, wherein the cut-off switch is coupled between the voltage supply and an input voltage node of the power converter, wherein setting the cut-off switch in the ON state couples the voltage supply to the input voltage node;
• and
• while the cut-off switch is in the ON state:
• sending, by a second controller of the power converter, a gate control signal to a power switch of the power converter, wherein the gate control signal turns the power switch on and off alternately;
• monitoring, by the first controller of the protection circuit, the gate control signal and a first current flowing through the cut-off switch;
• and
• in response to detecting that the first current is above a first pre-determined value when the gate control signal indicates an OFF state for the power switch, declaring, by the first controller of the protection circuit, an electrical short of the power switch.

A power protection circuit configured to be coupled between a voltage supply and a power converter, the power protection circuit comprising:

• a controller;
• a cut-off switch, wherein a first load path terminal of the cut-off switch is configured to be coupled to the voltage supply, and a second load path terminal of the cut-off switch is configured to be coupled to the power converter;
• a driver circuit coupled between the controller and the cut-off switch;
• a current sensing circuit coupled to the cut-off switch and configured to sense a current flowing through the cut-off switch;
• and
• a current measurement circuit coupled between the controller and the current sensing circuit and configured to provide a first measurement of the current flowing through the cut-off switch;
• wherein the controller is configured to:
• assert a drive signal to the cut-off switch;
• monitor the current flowing through the cut-off switch based on the first measurement;
• detect that there is a current flowing through the cut-off switch when the power converter is activated and when a gate control signal of the power converter indicates an OFF state for a first current path of the power converter, the first current path being coupled to the second load path terminal of the cut-off switch;
• and
• upon detecting that there is a current flowing through the cut-off switch when the power converter is activated and when the gate control signal of the power converter indicates the OFF state for the first current path of the power converter, switch off the cut-off switch.