Single-inductor Multiple-output Converter For High-power LED Applications Based On SiC SBD

Due to the greenhouse effect and international petroleum crisis,it is increasingly urgent to find a light source with high luminous efficiency to reduce the energy consumption in lighting field.Light-emitting diodes(LEDs)have tremendous advantages,including high efficiency,long lifetime,compact size,rich color and very low maintenance cost over the traditional lighting sources.LED driver plays an important role in the performance and life of LEDs.In recent research,LED drivers mainly focus on small and medium power LED applications and single-stage driver.There is great significance in studying the LED driver for high power applications due to its advantages of small size and low power consumption.For high power LED applications,multiple LEDs are usually arranged in parallel LED strings to obtain the desired luminance.Single-inductor multiple-output LED driver is usually used to reduce the voltage requirement.However,there are many problems in designing a single-inductor multi-output LED driver for high power applications,especially the EMI problem caused by switching and high-side NMOS driver circuit of the branch switches.Therefore,research on the single-inductor multi-output LED driver circuit for high power applications is of great significance.For high efficiency and high power applications,the switching frequency,output voltage and output power of the proposed single-inductor multi-output LED driver circuit for high power applications based on Si C SBD in this paper are designed to be 156 k Hz,150 V and 70 W respectively.Therefore,the source voltage of the branch switches in the power circuit will be as high as 150 V when the circuit is in a steady state.Therefore,a high-side MOSFET driver circuit based on charge pump is designed in this paper.By maintaining the constant voltage difference between VB and the VS terminal of the driver chip,the high-side drive of the branch MOSFET switches can be realized,so that the output voltage of the circuit can be as high as 150 V.In addition,with the single-inductor multi-output topology and timemultiplexing control scheme,the inductor current is time shared by each LED string,so that the designed circuit can be used to drive three LED branches as load and the circuit output power can reach 70 W.In order to improve the efficiency of the power supply and reduce the EMI effect of the circuit,silicon carbide(Si C)Schottky Barrier Diode(SBD)is used as freewheeling diodes instead of silicon(Si)Fast Recovery Diode(FRD)in this paper.The main characteristics of Si C SBD are:(1)Short reverse recovery time and small reverse recovery charge;(2)The characteristics are not easily affected by temperature.The reverse recovery current amplitude is decreased by 50% comparing with circuits based on si diodes,thus the simulation efficiency is up to 98.75% and the experiment results show that the system efficiency can be as high as 92.5%.The main contents of the study are as follows:(1)The working principle of DCM buck circuit,control circuit design,high-side NMOS driver circuit and single-inductor multioutput technology are studied theoretically.(2)Based on the theoretical research,the power circuit component parameter design and selection are given,the control circuit and driving circuit design are fully considered and analyzed.Finally,the circuit is built and simulated in the Cadence PSpice platform.The simulation results show the proposed LED driver circuit can be used to drive three LED strings and 144 LEDs as load,thus it can be used for high efficiency and high power LED applications.Si C SBD can effectively reduce the peak amplitude of the reverse recovery current to improve circuit efficiency.(3)Based on the simulation results,the PCB schematic and layout of the circuit are drawn under Altium Designer,and test of the prototype is made to verify the above design.The measured output voltage,output power and test efficiency can reach 150 V,70W and 92.5% respectively.