Molecular Crystals and Liquid Crystals, Vol.618, No.1, 1-9, 2015
Red/Infrared LED Unit with Moderate Light Intensity and Low Heat Generation for Personal Phototherapy Applications
A new phototherapy unit for personal and home application is developed based on red and infrared LEDs. The wavelengths of the LEDs used are 660nm for red light and 840nm for infrared. The array of red and infrared LEDs were designed to generate mixture of red and infrared light and the current flowing through red and infrared LEDs were driven by using micro control unit (MCU) so that the light output and the heat generated from LEDs could be controlled in order not to exceed the certain limit. Light output from the personal phototherapy unit depends on the current flowing through red and infrared LEDs. The current can be controlled by MCU and constant current LED driver ICs by adjusting the duty ratio of the driving pulse generated by MCU and the operation time of the phototherapy unit is also controlled by MCU. The average red and infrared light output from the phototherapy unit developed for personal application was set to 50 mW/cm(2). The surface temperature of the phototherapy unit after 10 minutes operation did not exceed 41 degrees C at the light output of 50 mW/cm(2) while LEDs were in contact with the skin.