Segmented LED Driver And Its Application In LED Light Communication

LEDs as the fourth generation light source,have the incomparable characteristics of high luminous efficiency,small volume,long life span and environmentally friendliness.So LEDs have been widely used in the lighting field.In addition,LEDs also have the advantages of good modulation performance,no electromagnetic interference,high response sensitivity.In recent years,the application of LEDs has expanded from the field of lighting to the field of visible light communication.Therefore,it’s a future development trend of LED to achieve both lighting and communication functions in future.However,to achieve high efficient LED lighting and LED visible light communication,it is needed to design a high performance LED driver.With the development of high voltage LED(HV-LED)and bulb thermal insulation technology,the high voltage isolation in LED driver is no longer a problem,and the price of LED is getting cheaper and cheaper.Thus,the non-isolated LED drivers have gained rapid development because of high efficiency and small volume.The piecewise current-controlled high voltage LED drivers are based on high voltage linear driving topology,and this kind of LED driver has better performances.It not only brings improvement to flicker problem,power factor,efficiency and the implement of dimming control,but also makes it possible to achieve small volume and can be easily integrated,because transformers,large inductors or electrolytic capacitors are not required in such kind of LED driver.Therefore,the piecewise current-controlled high voltage LED drivers have great application value and development prospects.This dissertation includes two parts,in the first part,a BJT-type segmented LED driver was proposed based on the existing segmented LED driver.The proposed LED driver not only has a high overall performance,but also can modulate the information very conveniently.In the second part,the LED visible light communication is studied and realized based on the proposed BJT-type segmented LED driver topology.The main contents of the whole dissertation are as follows.In this dissertation,the operation principle of the segmented current-controlled LED driver is introduced in detail.The ideal waveforms and theoretical calculation formulas are given.The loss of the circuit and the key factors which can influence the performance of piecewise current-controlled LED driver are analyzed too.In consideration of the circuit efficiency,power factor and total harmonic distortion,the principle of selecting the total number of LED beads,the phase coefficient and the section number of LED is presented.Secondly,in order to avoid the difficulty in driving the MOSFETs when the power supply is directly derived from the high voltage AC input,a BJT-type segmented LED driver was proposed in this dissertation.By introducing a sinusoidal input-current shaping strategy and an input-adaptive current control strategy,the proposed LED driver can perform high efficiency,high power factor,low total harmonic distortion and small output power fluctuation in wide input voltage range.Besides,the driver is very small in size,and the cost is very low.For experimental verification,a 5-W prototype LED driver was implemented.The test results show that the prototype LED driver(without any input filter)had the PF from 0.95 to 0.98,the THD40 from 18% to 33%,the efficiency from 80% to 86%,and the output power fluctuation of only ±8.4% while the input voltage covered 220 V±13.8%.Furthermore,the harmonic quality of the input current mostly satisfied the EN61000-3-2 Class D standard.Finally,based on the above advantages of segmented current-controlled LED driver,a visible light communication device was implemented based on the piecewise sinusoidal current-controlled LED driver.The whole scheme of LED visible light communication based on segmented sinusoidal current-controlled LED driver is introduced in detail.The hardware circuit and software design of transmitting device and receiving device controlled by TMS320F28027 are introduced.The transmitting device can work in the input voltage range of 190 V to 250 V,the circuit power factor(PF)is greater than 0.96 and the THD40 is between 21% and 24% when the data is not transmitted.The circuit input power can be stabilized at about 6 W.In addition,the data transmission and reception performance of the whole communication device and the receiving device are tested.The test results show that the transmitter and the receiver of the visible light communication device can transmit and receive data within about 2 meter,and the error rate is lower than 0.14% under the existing test conditions.