Semiconductor device with independent over-current and short-circuit protection

A semiconductor device adapted to monitor and protect against over-current and short-circuit in a load device, said device comprising, in combination:

• at least one current-sensing semiconductor element having collector and emitter layers adapted to be connected to respective terminals of a load device to be protected, a gate layer, and at least one current-sensing layer having an area smaller than the area of said emitter layer adapted to produce two or more sensing-currents proportional to the current produced by the emitter layer;
• and
• control circuit means coupled to the gate layer of said semiconductor device for controlling a flow of main current in said semiconductor element, said control circuit means comprising:
• first circuit means including first resistance means for receiving a first selected one of said sensing-currents from said semiconductor element, and a constant voltage device for applying a fixed voltage to the gate layer of said semiconductor element in response to said main current when exceeding a predetermined short-circuit level, and
• second circuit means including comparator means, a reference voltage source connected to a first input terminal of said comparator means, and second resistance means for receiving a second selected one of said sensing-currents from said semiconductor element for turning said semiconductor element off in response to said main current when exceeding a predetermined over-current level, said second resistance means being connected to a second input terminal of said comparator means;
• whereby voltages developed by sensing-current from said semiconductor element flowing through said first and second resistance means are independent of each other to allow independency of said predetermined short-circuit and over-current levels.