Patent ID: 8686666
Filing Date: 2014-04-01
Classification: G01K,H05B

Abstract:
1. A method for determining a temperature of at least one light emitting diode (LED) in a circuit which includes (i) a power supply for powering the LED and (ii) a thermistor electrically connected in parallel with the LED, the thermistor having an effective resistance range that is lower than a reverse bias resistance of the LED and that is higher than a forward voltage resistance of the LED, where the LED is operable to generate light, the method comprising: providing an operating current and an operating voltage to the LED; superimposing a current pulse on the operating current, superimposition of the current pulse causing a relatively larger amount of the current pulse to flow through the thermistor and a relatively smaller amount of the current pulse to flow through the LED; determining a temperature of the thermistor based on the amount of the current pulse flowing therethrough; sensing a magnitude of a voltage pulse across the LED resulting from the applied current pulse superimposed on the operating current; and determining an operating temperature of the LED at the provided operating current based on a magnitude of the amount of the current pulse caused to flow through the LED and the magnitude of the voltage pulse.