Abstract: LED lamp circuitry that emulates an incandescent lamp's behaviour upon remote verification of the LED lamp. The invention presents a fuse blow-out circuit and a cold filament detection circuit permitting the use of LED lamps in applications, such as railway signal light applications, where there is a need for remote monitoring of the lamps, while keeping the advantageous features of lower power consumption and longer life. The invention also provides a control circuit for enabling/disabling the power supply to LED lamps in relation to the level of the line voltage. The advantage of this embodiment is to avoid unwanted functioning of the LED lamp caused by interference from surrounding electrical cables.

Abstract: A sensor circuit for detecting a current supplied to a non-linear light-emitting diode (LED) and for producing a current reading dependent on temperature. The sensor circuit comprises first and second serially interconnected resistors also connected in series with the LED, and a temperature-dependent impedance connected in parallel with one of the first and second resistors. At least a portion of the current through the LED flows through the sensor circuit to enable the first and second serially interconnected resistors and said temperature-dependent Impedance to produce a variable voltage signal representative of the current through the LED and dependent on temperature.

Abstract: A sensor circuit detects a current supplied to a set of light-emitting diodes and produces a current reading dependent on the temperature of operation of these light-emitting diodes. The sensor circuit comprises first and second serially interconnected resistors also connected in series with the set of light-emitting diodes. The sensor circuit also comprises a temperature-dependent impedance connected in parallel with one of the first and second resistors. At least a portion of the current through the set of light-emitting diodes flows through the sensor circuit to enable the first and second serially interconnected resistors and the temperature-dependent impedance to produce a variable voltage signal representative of the current through the set of light-emitting diodes, this variable voltage signal being dependent upon temperature. The above sensor circuit finds application in a substantially constant intensity light source.