Patent ID: 7656631

Claim:
A circuit protection arrangement for an electronic circuit having a circuit power source, operable to supply operating current, for passage through a load including at least one semiconductor junction device, at an operating voltage sufficient to bias the semiconductor junction device into conduction and control means having output port means operable to provide thereat, or inhibit therefrom, an enabling signal for effecting supply of power to said load from the source, the protection arrangement comprising: a supply switch, responsive to said enabling signal to effect or inhibit supply of power to said load from the source, and off-line load characteristics sensing means, arranged to be coupled to the load where fed with operating power by the supply switch and operable, absent supply of load power to the load from the supply switch, to sense a voltage level across the load, including off-line threshold comparison means operable to compare the sensed voltage level with at least one stored value, the or each stored value being representative of a threshold of a load characteristic that is indicative of a correctly functioning semiconductor junction device, and responsive to a threshold comparison decision indicative of the load characteristics being inconsistent with those of a correctly functioning semiconductor junction device load, to inhibit provision of the enabling signal at said output port means; wherein the off-line load characteristics sensing means comprises off-line load conduction sensing means including a sensing current generator and is operable, absent supply of power to the load from the supply switch, to effect passage through the load of a sensing current having a value that is less, for a semiconductor junction, than the forward conduction threshold thereof, and to sense the voltage level across the load in response to said sensing current, and the off-line threshold comparison means is operable to determine if the sensed voltage level is below a primary stored value, predetermined as the minimum for said sensing current consistent with a semiconductor junction and maximum for the load having conduction characteristics from which the circuit requires protection from the application of said operating power, and respond to said voltage level being below said primary stored value to provide an unfavorable threshold comparison decision to effect inhibition of said enabling signal.