Power LED junction temperature readout circuit based on an off-the-shelf LED driver

A circuit is presented for the on-line measurement of the junction temperature (TJ) of power LEDs. The circuit is integrated with, and makes use of, an off-the-shelf LED driver, so that the proposed architecture can be easily made compatible with existing high-end luminaire platforms. The measurement technique, based on the linear junction voltage vs. temperature relationship, shows good precision and repeatability among devices with the same part number, with an absolute error below 3 °C.