Intelligent solid state relay/breaker

A solid-state relay/breaker having over-current characteristics of a slow-blow fuse of the type used to control high power AC or DC loads, the relay/breaker being commanded to turn on or off by a digital control signal comprising:

• at least one pair of MOSFET power transistors controlling a load current;
• a current sense path sensitive to at least three different frequency bands providing a feedback value proportional to said load current, said current sense path being sensitive to both AC and DC load currents;
• a signal processing circuit coupled to said current sense path for turning off said MOSFET power transistors after a delay using a pair of control signals when said load current exceeds a predetermined threshold, said delay being related to said load current, said control signals having a fast turn-on slew rate and a slower turn-off slew rate;
• said signal processing circuit also acting in response to a turn-on/turn-off command to switch said MOSFET power transistors and said current sense path off or on, switching of said MOSFET power transistors and said current sense path occurring with staggered timing.

A method for providing a slow-blow solid-state relay breaker action comprising the steps of:

• providing a MOSFET power switch transistor pair to switch current from a load;
• providing a current sense transistor to provide a bypass current proportional to load current flowing through said MOSFET power switch transistor pair;
• providing signals in at least three different frequency bands for determining if said bypass current is within range;
• providing delayed turnoff to said MOSFET power switch transistor pair using a first control signal when said bypass current exceeds a predetermined threshold, said delayed turnoff related to said bypass current;
• turning on said MOSFET power switch transistor pair using a second control signal before turning on said current sense transistor when starting said solid-state relay/breaker;
• and wherein said first control signal has a faster slew-rate than said second control signal.