Devices and methods for LED life test

A lifetime test equipment for a plurality of light-emitting diodes (LEDs) comprising:

• an oven having an oven temperature, wherein the LEDs are disposed in the oven, the oven gradually changes the oven temperature during a first period and sustains the oven temperature at a predetermined oven temperature point during a second period;
• a control module for providing a first current control signal, a second current control signal, a voltage measurement signal, and a switch signal;
• a first current source for providing a first current according to the first current control signal;
• a second current source for providing a plurality of second currents according to the second current control signal, wherein each of the second currents corresponds to one of the LEDs;
• a power switch unit for outputting the first current or the second currents to the LEDs according to the switch signal;
• a voltage meter for measuring forward voltages of the LEDs according to the voltage measurement signal;
• and
• a processing module;
• wherein for each of the LEDs, the processing module calculates a junction temperature of the LED according to the forward voltage of the LED and a variation relationship equation between the forward voltage of the LED and the oven temperature.

A lifetime test method for a light-emitting diode (LED) disposed in an oven, comprising:

• during a first period, gradually changing an oven temperature;
• obtaining a variation relationship equation between a forward voltage of the LED and the oven temperature;
• during a second period, sustaining the oven temperature at a predetermined oven temperature point;
• during the second period, providing a decay test current to the LED, and at every predetermined time interval, providing a first current to the LED to obtain a forward voltage of the LED;
• and
• calculating a junction temperature of the LED according to the variation relationship equation and the obtained forward voltage.