A Current Compensation Strategy For Multi-Segmented LED Driver

In view of the many advantages of LED(Light Emitting Diode),it has been widely used in various occasions for illumination.Because LED has the ability to be modulated quickly,it has been further developed in the field of visible light communication.LED driver is very important for LED,just as human heart is very important for people.According to the working mode of power devices,LED driver for illumination can be divided into two categories: switching mode and linear mode.Although the current switch-mode LED driver products occupy an absolute advantage in the market,for the application of several-watt AC input,the multi-segmented linear LED driver has the advantages of long life,small size,low cost,easy realization of PF,THD and so on,which has higher performance-price ratio than traditional switch-mode LED lighting driver.However,there is a common problem in the illumination mode of the multi-segmented linear LED driver — the circuit efficiency and the input current of the electrical indicators,PF,THD values can not be optimized at the same time.When the multi-segmented linear LED driver is used in visible light communication,if the communication mode of intensity modulation and direct detection is adopted,the electrical index of circuit current is seriously affected.In order to improve the existing problems of the multi-segmented linear LED driver in the mode of illumination and visible light communication,a current compensation strategy for the multi-segmented linear LED driver is proposed in the thesis.By comparing the two typical multi-segmented linear LED driver topologies for illumination,the common contradictions in the circuit are revealed.In order to verify the feasibility and effect of input current compensation,a multi-segmented linear LED driver prototype is designed and manufactured under illumination and VLC modes respectively.The prototype LED driver adopted the input-voltage adaptive current control strategy which combines current compensation,several input-voltage static and dynamic hysteresis regions used.Some experimental results show that the efficiency of the prototype is higher than that of the prototype without current compensation in illumination mode.In the visible light communication mode,the prototype efficiency has a small loss when using current compensation strategy,but its PF value,THD value and other electrical indicators have been greatly improved.The input current compensation strategy for the multi-segmented linear LED driver proposed in this thesis can improve the existing problems of the circuit in illumination mode and visible light communication mode.However,the energy of the current compensation has not been effectively utilized,and a non-destructive multi-segmented linear LED driver which can collects the energy of the current compensation and feedback to the control circuit can be designed to make full use of the energy to further improve the working efficiency of the whole circuit.The multi-segmented linear LED driver for VLC mode current compensation can be further optimized to achieve seamless current compensation.