Method and apparatus for detecting excessive current draw in an electrical load

摘要

A method and apparatus are disclosed for detecting excessive current draw in an electrical load particularly of the type having an in-rush current when first energized. The electrical load is connectable to an energy source through a current sensing circuit and an actuatable switch. The current sensing circuit provides a load sense signal that varies in response to current draw by the load. A control signal is provided to actuate the switch. A coupling network temporarily couples the control signal to the load sense signal to offset the change in the load sense signal resulting from current in-rush. The load sense signal is compared against a reference signal. The comparator outputs a signal indicative of whether the load sense signal is greater or less than the reference signal. One signal from the comparator is indicative of excessive current draw. The temporary coupling of the control signal with the load sense signal prevents the comparator from indicating an excessive current draw during current in-rush as long as the current draw does not reach a very large value, such as would occur during a short circuit. The output of the comparator is ANDed with the control signal for control of the switch.