Research On LED Driver With High Power Factor And Low Output Ripple

Lighting Emitting Diode(LED)has the advantages of high brightness,low power,long life and so on.The development of LED lighting depends on the maturity and the improvement of the LED driver technology.Power factor and output ripple are important indicators which measure the performance of LED driver.In order to improve the power factor and reduce the output ripple,the cascaded LED driver is researched.Firstly,the research background and significance of LED driver are introduced.The principle and characteristics of LED are described.According to the domestic and foreign references,the research status of high power factor and low output ripple LED driver are summarized separately.The cascaded LED driver is studied.As an example,the conducting modes and the characteristics of a LED driver based on quadratic buck converter are analyzed.The main parameters is optimized.The theoretical analysis is verified by PSIM.Secondly,a novel interleaved LED driver based on quadratic buck converter is proposed.Using the interleaving technology,the original topology is optimized,the voltage stress of the switch device and the output ripple is reduced.Under the condition of different duty ratio,the operating modes of the main circuit are analyzed.The operating performances are analyzed in detail providing the basis for the parameter design.The theoretical analysis is verified by PSIM.Then,for the problem of input current zero dead zone in the interleaved LED driver,a novel interleaved LED driver based on Buck-boost cascading quadratic buck is proposed.On the basis of the original topology,a Buck-boost converter is cascaded sharing one switch.The conducting modes,the characteristics of the intermediate energy storage capacitor,the inductor operating in discontinuous current mode and the switching characteristics are analyzed in detail.Utilizing the characteristic of Buck-boost convertor conducting in discontinuous current mode,it eliminates the problem of input current zero dead zone and improves the total harmonic distortion.The power factor is approximately 1.At last,the experimental prototype of the proposed interleaved LED drivier based on Buck-boost cascading quadratic buck is designed and built.For the switching device selection,the maximum voltage and current stress are analyzed and calculated.The control and driving isolation circuit is designed.The results are consistent with the theoretical analysis by the experimental prototype.The validity of the theoretical analysis is proved once again.