Electronic switch with automatic protective turn-off followed by automatic reset

Claim 1

A switch comprising: a switch transistor having a control electrode and also having a controlled path for connection in a circuit to be switched; first means connected to said switch transistor for supplying control signals to said control electrode to render the controlled path conductive; trip means including a second transistor connected to said first means and in a bypass path from the control electrode of said switch transistor and activated by a potential difference across said controlled path exceeding a threshold value to close said bypass path and render said switch transistor non-conducting, the trip means being connected to receive said control signals via delay means and said potential difference without substantial delay, so as to permit operation of the trip means only after the expiration of a predetermined delay period following application of said control signals to the control electrode of the switch transistor; and said trip means also including control means comprising a third transistor with its control electrode supplied via an RC delay element from the control electrode of said switch transistor and coupled to said switch transistor to open said bypass path when rendered non-conductive thus rendering said switch transistor at least partially conductive at the expiration of a predetermined delay period following actuation of the trip means.