Theory And Technology Of Electromagnetic Compatibility In DC-DC Converter

Modern electronic information industry is developing towards intelligence and miniaturization,and the integration of electronic products is increasingly high,including the power supply part.Due to the high efficiency of switching power source,a large number of low-power consumption electronic devices adopt the DC-DC converter for power management.Since the voltages and currents of the power source of electronic products are regulated,the electromagnetic compatibility(EMC)of the DC-DC converter should be considered by electronic equipment which used the switching power source.The quality of electromagnetic compatibility will determine the stability of the electronic equipment in the complex electromagnetic environment.Electromagnetic compatibility requires that the output EMI signal power spectrum of any electronic devices meets the preset requirements;Any electronic device can tolerate an input EMI signal below a predetermined level.This is actually a bidirectional requirement to electronic device: the electronic device cannot produce the electromagnetism interference which is harmful to other devices,and the electronic device can bear the electromagnetism interference of a certain intensity.For DC-DC converter,DC-DC converter is the most important part of power supply system,reducing the electromagnetic interference(EMI)in DC-DC converter is an urgent problem to be solved,because the jamming signal can not only radiate through the free space,but also transmit through the power line,the power supply of electronic equipment will be affected.Therefore this paper will have a in-depth study on the conducted EMI suppression in DC-DC converter.Based on the principle of spread spectrum principle,this paper makes an in-depth study on suppression of conducting EMI in DC-DC converter using programmable pulse width modulation(PPWM)technique and grouped clocking technique.This work including three parts: theory,simulation and experiment:Firstly,the research background and significance of this work are emphasized,the development of EMI suppression methods based on spread spectrum(SS)principle is briefly introduced.Then the basic principle of spread spectrum theory,the principle of periodic carrier frequency modulation(PCFM),the principle of programmable pulse width modulation(PPWM),grouped clocking Technique and AC small signalequivalent model of DC-DC converters are described.Secondly,three modulations are used in DC-DC converter.These modulation methods combine the spread spectrum theory with AC small signal model of DC-DC converter,using the genetic genetic(GA)optimization algorithm.The three modulations are: unmodulated PWM technique,programmable pulse width modulation technique,grouped clocking technology.The feasibility of these three modulation methods is analyzed by theoretical deduction.The three techniques of the simulation results are compared,the programmable pulse width sequence obtained in the simulation will be used in the EMI experiment.Finally,based on the LM3424 DC-DC converter and the TMS320F28335 DSP controller,a measurement experiment of the output conducting EMI of the DC-DC converter is performed.The spectrum suppression effects of the three modulation methods are verified by experiments,namely unmodulated PWM technology,PPWM technology and grouped clocking technology,and the DC characteristics of the DC-DC converter are also measured.