NXP has come up with a method to make an LED’s light quality mimic an incandescent light bulb more convincingly, especially when dimmed. While an incandescent bulb’s colour becomes warmer while being dimmed, dimmed LEDs typically emit a colder light colour. NXP’s solution combines white and amber LEDs as a cost-effective way to create pleasing light colours. It implements logarithmic correction for eye sensitivity—an analytical model makes it possible to achieve the desired colour points during the dimming process. Real-time temperature correction also is essential for proper control of LED performance. The company developed and patented a technique called “sensorless sensing,” which measures LED junction temperature through the two existing wires to the LED. This effectively eliminates external temperature sensors. Temperature can be measured with a resolution of around 1°C using this method. Furthermore, self-calibration can be performed to account for the LED’s age.