Research On Independent Current-control Topology Structure For LED Color-mixing System

With the increasing demand for high lighting quality,the requirements for lighting control are becoming increasingly high.Lighting control can be divided into brightness control and color control.Brightness and color control refers to the control of light intensity and color,respectively.So far,the simplest and easiest way is to use different color light sources for color-mixing.Since LED has a lot of advantages such as low power consumption,fast response speed,easy control of brightness and chromaticity,etc.,it is generally used as the optimum light source for multi-channel color mixing to construct a chromaticity coordinates tracking system.Multi-channel topology structure for LED color-mixing system has been studied,and a novel LED driver topology with fully-decoupled independent-current control was proposed in this dissertation.In multi-channel LED color mixing system,due to the different thermal sensitivity for different color of LEDs,the currents of the different color LEDs have a big difference.The unbalanced current can shorten the life of LED with high current or even burn out all the LEDs in this channel.Besides,the luminous efficiency of the LED with low current will be reduced.However,most of prior-art rarely take current balancing into the consideration in color-mixing system.In addition,the cross-coupling issues exist in many independent control topologies for color mixing systems,so the complexity of control is increased because of the switching sequences.In order to address the current-unbalancing and cross-coupling issues,an independent current control topology structure based on Daisy-Chain transformer structure was proposed in this dissertation.The “Coupling-decoupling” mode makes the currents flowing through multi-channels independent and balancing.Firstly,the currents flowing through all channels are balanced with daisy-chain transformer structure;Secondly,the currents flowing through all channels are fully-decoupled with PWM control by connecting a switch in series with LEDs.Moreover,the energy can be flowing with two-directions by adopting a bidirectional energy converter.The forward energy converter is used to provide the energy to the LED,and the reverse energy converter is used to send the energy not consumed by the LED to the input.After theoretical derivation and analysis of this topology structure,a 3-channel RGB(Red-Green-Blue)LED color mixing drive topology circuit is designed.Simulation and experimental verification are implemented using PSIM software and laboratory prototype.The function of independent current-control and current balance of the independent current-control topology structure for LED color-mixing system is verified by simulation and experimental results.