A novel method to reduce the operating temperature of high power light-emitting diodes

High power light-emitting diode (HP-LED) is now commonly used in electronic devices. However due to its unique electrical characteristics, it places many obstacles on maximizing the benefits provided by HP-LED. One of the obstacles is the rise of junction temperature due to current ripple that is inherent in all switching power supply. This affects the performance of HP-LED such as wavelength, luminance and life time which is difficult to predict for each HP-LEDs. There are many different methods to reduce the ripple. The most common and simplest solution is by using an filtering capacitor. However this usually requires a large capacitor that may not be desired in certain application. Several possible solutions were proposed in the past and one of them uses a linear regulator to compensate the ripple. But due to the way this technique is implemented, it has accuracy and efficiency problems. Therefore an improved active filter using operational amplifier to smooth the output ripple with enhanced accuracy and higher efficiency is introduced in this paper.