Research On A Single-stage LED Driver Combined With Visible Light Communication Modulation

The rapid development of the communication techology in the 21 st century has changed people’s lifestyles,the demand for communication is getting stronger for people.At the same time,Light Emitting Diode(LED),Which is the the fourthgeneration lighting source,has been widely promoted and used in the market due to its advantages of low energy consumption,long life,green environmental protection,and high luminous efficiency.The emergence of LED beyond lighting technology has expanded in the field of communication,a novel wireless communication technologyVisible Light Communication(VLC)is produced by the advantages of LED modulation performance and fast switching speed.The traditionally used radio frequency power amplifiers have disadvantages such as high cost,low efficiency and low power and so on.Therefore,the research on high-efficiency and high-power LED driver combined with visible light communication modulation has theoretical significance and engineering practical value.An AC-DC single-stage large-ratio step-down LED driver circuit to meet lowvoltage output LED applications is proposed in this paper.The proposed circuit topology structure,the operating modes are analyzed in detail,the input and output voltage transformation ratio under the mixed operating principle and process are derived,synchronous rectification characteristics and key parameters are analyzed and designed in detail.A single closed-loop PI control strategy,using digital control to achieve constant current output,is analyzed and designed.A computer simulation analysis is carried out to verify the effectiveness and feasibility of the proposed circuit.Based on the BPSK modulation strategy of visible light communication,a hybrid closed-loop control strategy for the proposed LED driver is proposed.The modulation strategy is based on the theory of binary phase shift keying(BPSK),which controls the current ripple phase by changing the phase of the PWM carrier from 0 to π and correspondingly controlling the on and off of the two switches to achieve data communication.The TMS320F28335 DSP chip is used in this paper to change the counting method inside the DSP chip through the interrupt program to realize the function of variable phase of carrier and generate the corresponding data carrier.Finally,the computer simulation experiment was carried out with PSIM simulation software.Finally,a prototype with AC input of 185～265Vrms/50 Hz and constant current output of 1A/25 W was designed and set up.A low voltage constant current output with a large step-down ratio within the rated input range was achieved.The input current harmonic component meets the IEC61000-3-2 Class C harmonic limit standard,and the power factor(PF)is higher than 0.965.The modulation and demodulation of VLC data transmission was relized by using proposed hybrid control strategy.At rated load,with VLC,the highest efficiency of the prototype is obtained up to 87.63%,the experimental results was get to verify the feasibility of the proposed circuit and proposed control strategy.