Method and System for Intrinsic LED Heating for Measurement
OwnerMark McCord, Yu Guan +1inventors
InventorsMark McCord, Yu Guan, James George
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Abstract
The present disclosure provides methods and apparatus for testing light-emitting diodes (LEDs), for example, measuring the optical radiation of an LED. In a method, a pulse-width modulated signal is provided to the LED. One or more characteristics of the PWM signal are varied so as to provide a forward voltage, Vf, corresponding to a target junction temperature, Tj, of the LED. The optical radiation of the LED is measured when the LED obtains the target junction temperature.
Claims23
A method for measuring optical radiation from a light-emitting diode (LED), comprising:
- providing a pulse-width modulated (PWM) signal to the LED, the PWM signal having current pulses with a duty factor, a pulse width, an amplitude, and a frequency;
- adjusting the duty factor, the pulse width, the amplitude, and/or the frequency of the current pulses to provide a forward voltage, Vf, which corresponds with a target junction temperature, Tj, of the LED;
- and
- measuring, when the target junction temperature is obtained, the optical radiation of the LED during a current pulse.
An LED test apparatus, comprising:
- a stage configured to hold one or more LED for testing;
- a signal generator for providing a power signal to an LED in the stage, and wherein the signal generator is configured to provide a PWM signal wherein the signal generator can adjust a duty factor, a pulse width, an amplitude, and/or a frequency of the PWM signal such that the LED operates at a target junction temperature, Tj;
- and
- a photospectrometer for measuring an optical radiation of the LED in the stage.
A method for calibrating an LED test apparatus, comprising:
- providing a pulse-width modulated (PWM) signal to an LED calibration standard, the PWM signal having current pulses with a duty factor, a pulse width, an amplitude, and a frequency;
- adjusting the duty factor, the pulse width, the amplitude, and/or the frequency of the current pulses to provide a forward voltage, Vf, which corresponds with a target junction temperature, Tj, of the LED calibration standard;
- measuring, when the target junction temperature is obtained, the optical radiation of the LED calibration standard during a current pulse;
- and
- calculating optical measurement offset values for the LED test apparatus according to the measured optical radiation of the LED calibration standard.
An LED driver comprising a PWM signal generator for providing a plurality of current pulses to an LED and configured to vary a duty factor, a pulse width, amplitude, and/or a frequency of the current pulses such that the LED operates at a target Tj.
A method for heating a light-emitting diode (LED) to a target junction temperature, Tj, comprising:
- providing a pulse-width modulated (PWM) signal to the LED, the PWM signal having current pulses with a duty factor, a pulse width, an amplitude, and a frequency;
- and
- adjusting the duty factor, the pulse width, the amplitude, and/or the frequency of the current pulses to provide a forward voltage, Vf, which corresponds with the target Tj of the LED.
An LED test apparatus, comprising:
- a stage configured to hold one or more LED for testing;
- an LED calibration standard affixed to the stage;
- a signal generator for providing a power signal to an LED in the stage;
- and
- a photospectrometer for measuring an optical radiation of the LED in the stage or the LED calibration standard affixed to the stage.
Dependencies are inferred from the claim text.