Wide-Range Dimming And High-Power LED Driver Based On Single Inductor And Multiple Output Structure

Compared with the traditional lighting sources,lighting-emitting diode(LED)has the obvious advantages of high luminous efficiency,energy saving,environmental protection,long life,easy maintenance and dimming.Since LED is a semiconductor diode with typical PN junction voltage characteristics essentially,so that the design of LED driving circuit is very important.At present,the development of LED drive circuit is fast at home and abroad,especially in reducing the volume of drive circuit and reducing power consumption,such as single inductor multiple output(SIMO)LED driver circuit,which obviously reduces circuit cost and realizes the drive of multiple parallel LED strings.However,there is still much to be explored in high-power LED driving circuit and flexible dimming circuit design.This paper will focus on this research direction.In different environments,people have different requirements for the brightness of LED lamps.The main content of this paper is to design a high-power LED driver based on single inductor and multi output circuit to achieve wide-range dimming.In the traditional PWM dimming circuit,the inductor has a large overshoot current at the instant of the conduction of the dimming switch.It will easily burn the device and affect the stability of the current passing through the LED lamps.Consequently,how to effectively suppress the overshoot current of the inductor is a key point of this paper.At the same time,in order to achieve a wide range dimming of LED,it is necessary to clarify the timing relationship between switches in the circuit at first.Different timing relations may affect the efficiency of the circuit,and the wrong timing relation will cause the circuit to not work properly.In this paper,the LED driving circuit designed in this paper is based on the SIMO structure,adopts BUCK conversion circuit,the input voltage is 150 V,the output voltage is 80 V,the output terminal is three parallel LED strings,each LED string has 24 series LED lamps,the output power is 84 W,the main switch operates at 200 k Hz,the branch switch and the dimming switch operates at 10 k Hz.In order to avoid the interference between the three branches,timing division multiplexing is used in the conduction of the three branches.At the same time,the paper adopts the sample and hold circuit to restrain the inherent defect of the PWM dimming.The wide-range dimmable LED driver designed in this paper can realize wide-range dimming of 5%~100% and is suitable for high power LED lighting applications.At the same time,the switch control circuit in this paper adopts analog control,which can achieve higher precision dimming on the basis of meeting the timing relationship of each switch.In addition,high power circuit is prone to generate electromagnetic interference(EMI),thus,we need to consider how to avoid the EMI problem when designing the circuit.The main contents of this paper are:(1)to understand the current development status and development prospect of LED drive circuit and analyze the significance of wide-range dimming circuit;(2)analyze the system modeling of voltage BUCK driving circuit,understand the theoretical basis of compensation network design,and analyze the factors which need to be considered in selecting the driving circuit;(3)calculate the parameters of the main components in the circuit design,such as master inductance and output filter capacitor,analyze the type of compensation network and calculate the parameters of components.The sample and hold circuit is used to effectively improve the defects of the traditional PWM dimming circuit.The timing relationship between switches is analyzed,and a reasonable switch control signal generation circuit is designed.At the same time,it designs a circuit that can effectively suppress the EMI in the high-power LED driver.(4)the circuit is built on the PSPICE platform,and the simulation is carried out to verify the circuit function through simulation results.Then draw the PCB board and complete the welding to test the function of the circuit.The test results are consistent with the simulation results,and verify that the circuit designed in this paper can achieve high accuracy and wide-range stable dimming for LED,and the impulse current of the inductor is effectively suppressed.And,it is verified that the circuit of this paper can realize the LED dimming with 5%~100% duty cycle in three branches.