ELECTRONIC SAFETY DEVICE Russian patent published in 2002 - IPC

FIELD: overcurrent and short- circuit protection of loads and power circuits of secondary power supplies. SUBSTANCE: device has power MIS transistor, control transistor, and voltage regulator diode; first leads of first and second resistors are connected to terminal for connecting plus lead of power supply and their second leads are connected, respectively, to first lead of switch and to collector of control transistor, the latter being also connected to voltage regulator diode cathode and through third resistor, to gate of power MIS transistor; control transistor base is connected to intermediate leads of switch and through fourth resistor, to load terminal and to first leads of first capacitor and fifth resistor whose second leads are connected to common wire of circuit, connected to the latter are also control transistor emitter, voltage regulator diode anode, source of MIS transistor which is connected through series-interconnected second capacitor and sixth resistor to drain of this transistor, second lead of switch, and, through fuse, terminal for connecting minus lead of power supply. Power MIS transistor drain is directly connected to load terminal. Newly introduced in device are first and second comparators and thermistor, the latter being in thermal contact with power MIS transistor case and its leads are connected to common wire and to input of first comparator; second comparator input is connected to terminal for power supply plus lead and outputs, to inputs of control device whose output is connected to control transistor base; when output signals of first and second comparators take values corresponding to logic 1, then output signal of control device cuts off control transistor for the time required to set steady conductive state for power MIS transistor; when output signal of one of comparators takes the value of 0, output signal of control device drives control transistor in conduction. Newly introduced in electronic safety device are also diode and seventh resistor; diode cathode is connected to cathode of voltage regulator diode, its anode is connected to gate of power MIS transistor and to one lead of seventh resistor whose other lead is connected to common wire of circuit. EFFECT: enhanced reliability. 2 cl, 2 dwg