Ground fault current interrupter circuit

A method for ground fault current interruption, comprising:

• comparing a signal representative of a difference of current flow to a load and current flow from the load to a plurality of threshold voltages;
• wherein each of the threshold voltages corresponds to a different value of the difference of current flow;
• and
• activating a fault signal responsive to determining that, for at least one of the threshold voltages, the signal representative of the difference of current flow exceeds the at least one of the threshold voltages in at least half of a predetermined number of previous alternating current cycles;
• wherein the predetermined number increases with lower values of the threshold voltages.

A method for ground fault current interruption, comprising:

• comparing a signal representative of a difference of current flow to a load and current flow from the load to a plurality of threshold voltages;
• wherein each of the threshold voltages corresponds to a different value of the difference of current flow;
• and
• activating a fault signal responsive to determining that, for at least one of the threshold voltages, the signal representative of the difference of current flow exceeds the at least one of the threshold voltages in at least half of a predetermined number of previous alternating current cycles;
• wherein:
• a first of the threshold voltages corresponds to a difference of current flow of 5 ma and the predetermined number of previous alternating current cycles is at least 64;
• a second of the threshold voltages corresponds to a difference of current flow of 20 ma and the predetermined number of previous alternating current cycles is at least 16;
• a third of the threshold voltages corresponds to a difference of current flow of 40 ma and the predetermined number of previous alternating current cycles is at least 4;
• and
• a fourth of the threshold voltages corresponds to a difference of current flow of 100 ma and the predetermined number of previous alternating current cycles is 2.

A ground fault current interrupter (GFCI) circuit, comprising:

• a plurality of comparators, each of the comparators configured to compare a threshold voltage to a signal representative of a difference of current flow to a load and current flow from the load;
• threshold generation circuitry configured to generate a plurality of different threshold voltages, each of the different threshold voltages provided as the threshold voltage for one of the comparators;
• a plurality of timer circuits, each of the timer circuits comprising:
• a filter counter coupled to one the comparators, the filter counter configured to activate a filter output signal responsive to the output of the comparator being active for longer that a predetermined time;
• wherein the predetermined time increases with lower values of the threshold voltage;
• a phase counter coupled to the filter counter, the phase counter configured to trigger a fault signal based on the filter output signal being active in more than half of a predetermined number of previous alternating current cycles.