Monitoring circuit for vehicle incandescent lamp - has parallel diode protecting precision current detecting resistor from overload

摘要

The monitoring circuit, for incandescent lamps in motor vehicles, has a precision resistor in series with each lamp and a circuit to monitor the voltage drop across the resistor. A diode (SD) shunts the precision resistor (R1) to limit the voltage across the resistor when current is flowing and thereby overloading. The diode may consists of several parallel diodes and is chosen so that its forward voltage is greater than the normal voltage drop across the resistor.