Patent ID: 6072681
Filing Date: 2000-06-06
Classification: H02H,H03K

Abstract:
A protection device for protecting a power line, the device comprising:(a) a transistor having an input electrode for receiving an input voltage signal, an output electrode for outputting the voltage signal to an electrical load via the power line and a control electrode for receiving a control signal;(b) a series circuit coupled between the input voltage signal and a voltage return, the series circuit including:(i) a first bias resistor coupled to the voltage return,(ii) a positive temperature coefficient (PTC) element coupled from the input voltage signal to the first bias resistor, the PTC element being also thermally coupled to the transistor; and(c) a triac coupled between the input voltage signal and a reference voltage level, the triac having a gate terminal coupled to a node between the first bias resistor and the PTC element for receiving an activating signal, the triac also having a first anode connected to the input voltage signal, and a second anode forming an output node for outputting the control signal to the control electrode of the transistor upon receiving the activating signal;(d) a second bias resistor having a first end coupled to the second anode and a second end coupled to a voltage return;wherein the PTC element detects a fault condition on the power line and causes the activating signal to be sent to the triac upon detection of the fault condition;wherein upon receiving the activating signal, the triac sends a control voltage to the control electrode of the transistor to latch the transistor into an off state; andwherein the transistor, once latched into the off state, remains in the off state even after the fault condition disappears.