Research On A Single-stage LED Driver Integrated Bridgeless Boost Circuit With LLC Circuit With VLC Modulation

LED has many advantages,such as low power consumption,high brightness,long life,small size,good dimming,no pollution,etc,which is known as the fourth generation of green light source and widely used in the lighting occasions.Visible light communication technology(VLC)can realize the dual function of communication and lighting by using the characteristics of fast modulation and fast response of LED.With the rapid development of LED,the research of LED driver has been carried out widely in industry and academia.The conventional two-stage LED driver requires two control circuits,which has the problems of high cost,control complexity and poor reliability.In order to solve the above problems,the single-stage LED driver has been widely concerned in recent years,which integrates the power factor correction unit with the DC-DC unit by sharing the same power switch.By integrating the bridgeless Boost circuit and LLC circuit,a novel bridgeless single-stage resonant LED driver is proposed to reduce the conduction loss and switching loss.Its one switch can achieve ZVS and the other one achieves ZCS.The bridgeless Boost circuit is designed in DCM operation,which can realize automatic power factor correction.The operating principle of the proposed driver,the characteristics of PFC unit and DC-DC unit are analyzed in detail in this paper.The key parameters are analyzed and designed in this paper,and the feasibility of the proposed driver is verified by simulation software and experimental prototype.A mathematical model of DC bus voltage is established and the relationship between the control variable D,fs and the DC bus voltage is analyzed.This paper adopts the APWM-PFM hybrid control strategy,in which the voltage feedforward loop is set to reduce the duty cycle of reusing MOSFET so that the amplitude of DC bus voltage can be reduced,and the current feedback loop is set to adjust the switching frequency for keeping output current constantly.The control strategy is realized by DSP digital control system.This paper analyzes the realization mechanism of APWM-PFM hybrid control strategy by TMS320F2812 in detail and designs the corresponding program flow chart.Modulation technology is an important condition for ensuring the quality and speed of VLC.Several common pulse modulation methods and OFDM modulation method are analyzed in detail and the difference between them is given.Using OFDM modulation method,a VLC modulation scheme for realizing OFDM signal injection based on the network transformer is presented,which is combined with the proposed driver.The VLC experimental tests are carried out under different conditions.A prototype with 90?135Vrms input and 2A/100W output is set up to verify the theoretical analysis.The experimental results shows that the highest efficiency is 91.45%,the power factor(PF)is higher than 0.985,the DC bus voltage range is 271?400V when the input voltage is within the range of 90?135Vrms.When the rated input voltage is 110Vrms,the efficiency is 90.68%,the power factor(PF)is 0.993,the harmonics distortion(THD)is 11.2%.