| 摘要 |
The invention provides a method for determining the light output level of a light emitting diode (LED), the LED being operated with a voltage over the LED and a current through the LED. The method uses obtaining (100) an LED input electrical power value (Pin) to the LED, obtaining (102) an a thermal power value (Pth), and determining (104) a LED output power from at least the input electrical power value (Pin) and the thermal power value (Pth). The thermal power value (Pth) is obtained using a temperature difference value between the temperature values measured at two different locations and a thermal resistance value (Rth). The invention also provides a circuit arrangement using the method, a LED driver IC using the circuit arrangement and a lighting system with at least one LED and such a circuit arrangement. |
