Design Of LED Screen Drive Circuit For DMB Applications

Sending information to LED screens via Digital Multimedia Broadcasting(DMB)is a new type of information publishing technology.Because the DMB system has the advantages of wide coverage,high security,and easy construction,this technology has been widely used in schools and scenic spots.The LED drive circuit for DMB applications is a key part of the technology,which is responsible for converting the demodulated DMB information into driving signals for the LED screen.At present,the LED drive circuit used in DMB system is mainly based on embedded software.Due to the limitation of the frequency and internal resources,it can only drive small-scale or low-gray LED screens,which cannot meet users' requirements for full-color and large sizes LED screens.This topic studies the above-mentioned engineering problems.It applies the characteristics of Microcontroller Unit(MCU)that are easy to control and program,and the ability of Field Programmable Gata Array(FPGA)to process data at high speed in parallel.A combined MCU + FPGA solution is designed.DMB information can be received,and parameters can be configured.The LED screen drive circuit of multiple color modes effectively expands the compatibility of DMB information displayed on the LED screen.The main work of the subject is as follows:1.The working principle and related protocols of data transmission in the DMB information distribution system and the basic principles of LED screen display are analyzed.Based on these,a combined design scheme of MCU + FPGA architecture is proposed.The embedded program in MCU is developed to be responsible for receiving and processing DMB data,realize the data communication with DMB receiving module and FPGA,and complete the process of converting DMB data into LED pixel dot matrix.2.This thesis uses Verilog HDL to describe the circuit in FPGA,which is responsible for driving and displaying the LED screen,including data buffer module,off-chip SRAM driver module and Gray modulation and scanning module.The design is based on the LED screen of the general-purpose chip and the special chip to design the driving circuit,so that it supports a variety of screens.All the above circuits are simulated and verified with Modelsim software to ensure the correctness of logic functions.3.The PADS software is used to complete the circuit board design of the overall plan,and a prototype is produced.Using the DMB transmitter and receiver in the laboratory,an experimental environment and a demonstration system were built.After testing,the designed circuit realizes the normal display of the LED screen,the display text is clear,supports multiple gray-scale full-color screen display,supports 2600 Hz refresh rate,and supports a maximum 1024*256 pixel full color screen,which can correctly receive DMB information to achieve synchronous display of all terminals.The size of the produced circuit board is 10.98cm*5.47 cm,which is easy to install in the LED screen and meet the needs of engineering applications.