Study On Multi-channel LED Drivers Based On Current Bus

Compared with the traditional lighting sources,light emitting diode(LED)has some prominent advantages such as high efficiency,energy saving,long lifetime,abundant colors,easy dimming control,high safety,non-pollution,etc.It is recognized as a new type of green solid-state lighting source,which has obtained rapid development and huge market applications in recent years.As one of the key parts of an LED lighting system,LED driver plays an important role in its overall performance and reliability.Therefore,it is very necessary to carry out continuous research on LED driver.Power factor correction(PFC),input and output electrical isolation,and flexible control for multiple-output currents are the core functional requirements of LED driver utilizing an AC source.Taking this as a starting point,this dissertation proposes a specific topology structure of DC current bus type(DCCB-type)distributed multiple-output unit.And then combined with the single-stage power factor correction technology,the AC-DC multi-channel LED drivers based on current bus are studied.The main research contents and innovation achievements of this dissertation are as follows:(1)The topology construction theories and methods for basic non-isolated DC/DC converter and non-isolated DC bus type distributed power system are proposed.Starting from the functional decomposition of basic non-isolated DC/DC converter topology,and combining with the basic circuit theory,four categories of basic non-isolated DC/DC converters have been deduced out in this dissertation.Thus,the corresponding topology construction methods have been formed.That is to say,voltage-type(V-type)functional units and current-type(C-type)functional units must be alternately cascaded.Based on the above ideas,the topology construction theories and methods for basic non-isolated DC voltage bus type(DCVB-type)as well as DC current bus type(DCCB-type)distributed power systems have been further researched,which provides theoretical support and basis for constructing a topology structure of DCCB-type distributed multiple-output unit.(2)A DCCB-type distributed multiple-output unit suitable for multi-channel LED drivers is constructed.The topology simplification for it has been completed by combining with multi-channel LED constant current driving application background.Taking three output currents as an example,two kinds of control methods for multiple-output currents,namely the synchronous control and independent control of multiple-output currents,have also been discussed in detail.Furthermore,aiming at the proposed two kinds of specific current control methods,the theoretical analysis,parameter design and related experiment research all have been carried out respectively.The experimental results prove the correctness and effectiveness of simplified DCCB-type distributed multiple-output unit as well as its multiple-output currents control methods.(3)A type of AC-DC distributed multi-channel LED driver topologies based on current bus are derived.1)By combining the Buck-Boost+Flyback single-stage isolated PFC circuit with the simplified DCCB-type distributed multiple-output unit in this dissertation,a two-stage AC-DC DCCB-type multi-channel LED driver utilizing a power frequency AC input source can be produced.Taking independent control of three output currents as an example,the theoretical analysis,parameter design and related experiment research for it all have been completed.Thus,the application of proposed DCCB-type distributed multiple-output unit in LED driver utilizing an AC source is realized.2)In view of the problems that the Flyback transformer volume is large and the voltage stress of secondary-side rectifier diode is high,this dissertation proposes to replace the original secondary rectifier diode of Flyback transformer with a voltage doubler rectifier(VDR).Thus,a two-stage AC-DC DCCB-type multi-channel LED driver with a voltage doubler rectifier can be achieved.Through theoretical analysis,parameter design and related experiment research,the effectiveness of proposed topology improvement method is verified.The actual isolation transformer volume can be reduced to about one-third of the original Flyback transformer,and the voltage stresses of two secondary-side diodes in the VDR can be reduced to about a quarter of the original secondary-side rectifier diode.3)Aiming at some existing problems of two-stage LED driver above,such as low conversion efficiency,large number of components and large volume of the DC bus inductor,further equivalent simplification for the two-stage AC-DC DCCB-type multi-channel LED driver with a voltage doubler rectifier above has been achieved from the perspective of functional equivalence.Therefore,a single-stage series-type multi-channel LED driver can be derived.Likewise,through theoretical analysis,parameter design and related experiment research,it has been proved that the proposed single-stage series-type multi-channel LED driver can still work stably,and the average values of multiple output currents can be fully independent controlled by adopting the independent closed-loop control strategy proposed in this dissertation.It has the characteristics of high input power factor,small size of isolation transformer,and no need to control the DC bus current separately.The conversion efficiency is improved by about 3% compared with the two-stage structure above.(4)A quantitative analysis and design method suitable for single-stage single-phase converter is proposed.The three kinds of AC-DC distributed multi-channel LED driver topologies based on current bus proposed in this dissertation have internal connections and obvious differences in operating modes.Based on the same design ideas and processes,the quantitative design of their circuit parameters all have been completed.The experimental results also prove the correctness and effectiveness of the proposed parameter design method.The above quantitative design method is also applicable to other types of single-stage single-phase converters,which has certain universality.