CIRCUIT PROTECTION DEVICES

摘要

The present invention provides a circuit protection device for protecting an electrical load (20). The device comprises a three-terminal switch-element (10) having first, second and third terminals, the first terminal for series connecting to the electrical load; a positive temperature coefficient (PTC) resistor (22) having first and second ends, the first end connected to the third terminal of the switch element; and a voltage divider circuit including first and second resistors (14, 16), the first resistor connected between a voltage source and the second terminal of the switch element, the second resistor connected between the second terminal of the switch element and the second end of the PTC resistor. According to the present invention, the switch element may be a metal-oxide-semiconductor transistor (MOSFET) or a junction field-effect transistor (JFET) and the first, second and third terminals of the switch element are drain, gate and source electrodes, respectively. The switch element may also be a bipolar junction transistor and the first, second and third terminals of the switch element are collector, base and emitter electrodes, respectively. Various other embodiments of the invention are disclosed.