Inverse-System Decoupling Control Of Constant Current Boost LED Drivers

Light Emitting Diode(LED)is widely used in the field of lighting due to its advantages of long life,low energy consumption,green and pollution-free.LED is a low-voltage DC nonlinear semiconductor device.When it is turned on,the small changes of voltage at both ends will make the current change significantly.Therefore,it needs a matching constant current drivers to make it emit light stably and reliably.However,it is difficult to design the controller with linear system theory because of the difficulty of building its linearization model.Aiming at the characteristics of constant current DC-DC LED drivers,this paper takes Boost LED drivers as an example,and proposes an inverse-system decoupling double current loop control method.Firstly,the large-signal averaged model of the main circuit of constant current Boost LED drivers is established.On this basis,in order to control the output current of LED accurately,a double current loop control structure is adopted.In order to reduce the difficulty of decoupling,this paper proposes to divide the model into four sub-modules: input disturbance module,load disturbance module,inner current loop module and outer current loop module,then decouple them separately.Through feedforward decoupling,the effect of input disturbance and load disturbance is eliminated.Based on the inverse-system theory,the inner and outer current loops are decoupled to eliminate the cross-coupling relationship between the inner and outer current loops.And they are compensated as first-order integral pseudo-linear systems respectively.This makes the input disturbance control,load disturbance control,inner current loop dynamic characteristic control and outer current loop dynamic characteristic control of constant current Boost LED drivers independent of each other,so that the linear feedback controller of inner current loop and outer current loop can be designed by applying linear system theory.The control object after decoupling compensation is a first-order integral system.The optimal feedback theory is used to design a linear feedback controller for the first-order integral system to realize the optimal control of tracking the given value.Finally,building a inverse-system decoupling control of constant current Boost LED drivers system simulation model on the MATLAB platform.And compared with the system simulation model of double current loop using the traditional PI control method.The simulation results show that the proposed control strategy can make the constant current Boost LED drivers have good steady-state and dynamic performance.At the same time,a test prototype was designed to further verify the correctness and effectiveness of the proposed control strategy from both electrical and optical perspectives.