Constant Current LED Research Articles

LCL-T resonant network-based modular multi-channel constant-current LED driver analysis and design

Multiple output LED drivers are necessary to achieve better performance and higher reliability in street lighting, tunnel lighting and LCD background lighting applications. Based on LCL-T constant-current characteristics, a modular multiple output LED driver is proposed in this paper. The LCL-T rectifiers are connected to the same voltage bus and work like current sources. However, since there are much higher voltage harmonics in the AC square bus voltage, it is very important to quantitatively analyze how these harmonics influence the precision of the output currents. In addition, all of the switches can achieve Zero Voltage Switching (ZVS) by proper design of the LCL-T network. Finally, a 200-W prototype with five channels is established with an efficiency of 92.25%.

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 660 nm for red light and 840 nm 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/cm2. The surface temperature of the phototherapy unit after 10 minutes operation did not exceed 41°C at the light output of 50 mW/cm2 while LEDs were in contact with the skin.

Design of Dimmable Quasi-Resonant Fly Back LED Driver Based on OZ9992

The paper designs a 30W dimmable constant current LED driver. It is designed by O2Micros OZ9992 control chip, and it use quasi-resonant flyback topology. It can achieve zero voltage to reduce switching losses. The LED driver has higher efficiency and can provide a stable current for LED lamps. It has good dimming performance, and is easy to operate. It is suitable for home, hotel and other occasions, and has broad application prospects.