Reserch On Dimmable LED Digital Driver Based On NB-IoT

LED lamps have become the mainstream lamps in the lighting field.However,the traditional LED driver usually does not integrate the wireless communication function,therefore,it is necessary to combine the single lamp controller to realize the operation of intelligent networking and intelligent dimming,resulting in the circuit structure becoming relatively complex.Narrow Band Internet of things(NB-IoT)wireless communication technology,digital PFC technology and digital PWM dimming technology are integrated into LED driver,and a dimmable digital LED driver with wireless communication function is designed in this paper.The power factor correction algorithm combined with discontinuous current control and critical current control is adopted to realize high power factor in a wide load range of10W-100 W and low input current harmonic.Combined with remote monitoring platform,the LED driver completes the functions of intelligent networking and intelligent dimming,which inproves the energy-saving level of LED lamps.The thesis analyzes the working principle of Boost power factor correction circuit and PWM dimming principle,and the state equation and output equation of Boost PFC circuit working in continuous conduction mode(CCM),critical conduction mode(CRM)and discontinuous conduction mode(DCM)are deduced.The PFC control algorithm,control principle and theoretical formula under three modes are analyzed.Besides,based on the theoretical derivation and design requirements,the important device parameters of EMI filter circuit,rectifier filter circuit,Boost PFC circuit and PWM dimming circuit in the main circuit are calculated and analyzed.Then,the article designes the control circuit based on DSP TMS320F28335,and its peripheral sampling circuit,driving circuit and NB-IoT communication circuit are analyzed and designed.Based on the hardware circuit,the digital LED driver can adjust the light according to the voltage of the dimming input terminal,or manually adjust the light according to the dimming value specified by the remote monitoring platform received by the NB-IoT communication module,or automatically adjust the light according to the dimming curve sent by the remote monitoring platform.Based on the hardware design and functional requirements of digital LED driver,the main program,timer 0 interrupt service program,timer 1 interrupt service program and serial port receiving interrupt program are written in the DSP program.The main program mainly realizes the initialization subroutine,the wireless communication subroutine necessary for NB-IoT module M5311 and dimming strategy subroutine;Timer 0 interrupt service program completes PFC inner loop control subroutine and circuit protection subroutine,while timer 1 interrupt service program realizes PFC outer loop control subroutine and system time subroutine;The serial port receiving interrupt program is responsible for storing the remote monitoring platform data received by M5311 into the array in real time.The thesis simulates and analyzes the digital LED driver in Simulink,meanwhile,the digital LED driver prototype and the test platform are built;S-Function is used to realize digital control and verify the influence of different PFC control algorithms on output voltage and input current,then,the optimal control mode is selected.The simulation results show that discontinuous current control and critical current control perform better at light load and heavy load,respectively;The NB-IoT communication function and main waveform of digital LED driver are tested on the test platform.The experimental results show that NB-IoT communication is reliable,and the effect of the input and output waveform performs well.